1. Farming systems that depend on an
intensive forage supply demand maximum
and consistent feed supplies, which favour
the use of successive forage crops in preference
tomore traditional ‘permanent’ pastures.
2. Establishment of successive forage
crops is only sustainable on a long-term
basis using no-tillage.
3. The integration of forage and arable
cropping systems is desirable in climates
that permit economic utilization of forage
crops by animals.
4. Farmers generally place lower values
on forage crops than on arable crops and
will more readily accept inferior results.
5. Drills for pasture and many forage
crops need to have more accurate depth
control and sow at shallower depths than
equivalent machines for arable crops.
6. Drills for pasture and forage crop species
need to be able to meter small seeds.
7. Forage crops should generally be
treated with the same care and attention as
arable crops, but they seldom are.
8. Drills for pasture need to handle tightly
root-bound soil and also utilize this covering
medium to advantage.
9. With pasture renovation by overdrilling,
there may be a trade-off between
providing a suitable environment for germination
and emergence and reducing competition
from the existing sward.
10. Because the drilling time of forage
crops and pastures is usually not as critical
as with arable crops, there is more opportunity
to wait for suitable weather to offset
substandard openers.
11. On a cost-recovery basis, blanket spraying
of the existing competition will give a
greater long-term return than band spraying,
which gives a greater return than no
spraying.
12. Cross-drilling slowly establishing
pasture species may produce greater shortterm
weed infestation than single-pass
drilling.
13. Drilling early in the autumn is likely to
produce more pasture production than later
drillings, provided adequate soil moisture
exists at the time.
14. Early autumn drilling and spring drilling
are likely to produce more weed problems
than later autumn drilling, especially
with slowly establishing pasture species.
No-tillage for Forage Production 183
15. Single-pass drilling in 75 mm rows
may produce a short-term yield advantage
with slowly establishing pasture species
compared with single-pass drilling in
150 mm rows.
16. Neither single-pass drilling in 75 mm
rows nor cross-drilling in 150 mm rows has
any long-term agronomic advantage compared
with single-pass drilling in 150 mm
rows, or any short-term advantage with
rapidly establishing pasture species.
17. With band spraying for overdrilling,
75 mm wide bands are preferred with
150 mm spaced rows.
18. With overdrilling for pasture renovation,
fertilizer should not be applied at the
time of drilling but should instead be
applied about 3 weeks post-emergence.
19. With complete pasture renewal, the
new pasture should be drilled and fertilizer
applied during drilling, similar to an arable
or forage crop.
184 C.J. Baker and W.R. Ritchie
13 No-tillage Drill and Planter
Design – Large-scale Machines
C. John Baker
A no-tillage seed drill is no more nor less than
a device designed to service the functions of
its openers.
While most of the desirable functions of
no-tillage drills and planters can indeed be
related back to the desirable functions of
their openers, other components and functions
are also important. These will be
examined in a general sense with no attempt
to approve or disapprove design criteria for
individual commercial drills or planters.
Manufacturers and designers who seriously
consider the desirable functions of
drills and planters and variations required
to achieve these most often will present a
range of design options. Consumers must
then ascertain for themselves what represents
the best value after having weighed
the risk, performance and cost factors.
For example, drills for pasture renovation
might not need to be as sophisticated as
those to establish cash crops, because
residue handling is seldom a high requirement
with pasture establishment and there
may be more time flexibility allowable in
choosing an appropriate sowing date. This
in turn permits a delay in drilling until
favourable weather patterns arrive. The target
sowing dates for cash crops, on the other
hand, are often dictated by a narrow window
of climatic opportunity or harvesting
and seldom allow the luxury of being able
to wait very long for favourable conditions.
Cash-cropping drills and planters, therefore,
must function to their maximum
potential with less dependence on weather
and therefore need to be more sophisticated
than pasture renovation drills.
This chapter considers large field-scale
and tractor-drawn machines. The following
chapter considers small field-scale and
animal-drawn machines. In both cases we
consider drill and planter design under
several headings:
● Operating width.
● Surface smoothness.
● Power requirements.
● Downforce application.
● Transport considerations.
● Matching to available power.
● Storage and metering of product.
Operating Width
The most important factors that should
influence the design width of no-tillage
drills and planters are the total time available
to establish a given crop and the tractor
power available to pull the machines.
Unfortunately, many converts from tillage
to no-tillage expect no-tillage to achieve the
© FAO and CAB International 2007. No-tillage Seeding in Conservation
Agriculture, 2nd edn. (eds C.J. Baker and K.E. Saxton) 185
same rates of ground coverage as each of
their previous tillage machines. Such expectations
fail to account for the fact that
no-tillage machines are only going to cover
the field once and can therefore afford to
operate at a slower rate of ground coverage.
Because most no-tillage drills and planters
are capable of operating at equivalent forward
speeds to tillage machines, this means
they can be narrower.
A sensible and practical comparison
was made by an English farmer, who
concluded that, so long as he could drill
with his no-tillage machine at the same rate
as he could previously plough, he would be
gaining by adopting no-tillage. Despite such
pragmatism, it is common to hear other
farmers demanding that no-tillage machines
must be the same width as conventional
tillage machines. Some machinery
designers accede to this request but in so
doing are forced to select openers with low
power demand. Almost invariably, the
lower the power demand from no-tillage
openers, the less work they do on the
untilled soil and the greater will be the risk
of biological failure.
For example, a farmer practising minimum
tillage will cover the field at least
twice and probably three times to establish
a crop. If each of the machines used for
minimum tillage (including the drill) was
4.5 metres wide, the effective working
width would be 1.5 metres (4.5 ÷ 3). And
yet many such farmers complain that a
3 metre wide no-tillage drill would be too
narrow for them, even although once-over
with a 3 metre wide drill would complete
the whole job in half the time that three
times over with 4.5 metre minimum-tillage
machines could achieve. While seemingly
simple, it is surprising how often this
argument is voiced.
For ‘diehard’ tillage exponents, such
an argument seems to be an excuse for
avoiding the issue. For others already practising
no-tillage with wide low-powerdemanding
drills, it reflects ignorance of
the benefits that the more sophisticated
no-tillage technologies offer (which are
almost invariably accompanied by greater
power demand).
While increases in both the power and
downforce demand from openers translate
into increases in tractor power and machine
weight, these are relatively cheap and
readily available inputs. Increases in biological
reliability and crop yield from
improvements in opener design are much
more expensive and sophisticated inputs.
Some operators choose to minimize power
or weight requirements rather than maximize
biological reliability. It is a matter of
how individual operators approach the
whole concept of no-tillage: whether they
are yield-driven or cost-driven.
Those that see no-tillage as shortcutting
tillage, but still regard tillage as the
benchmark, will probably rate cheapness,
maximizing working width and minimizing
power and weight requirements as high
priorities. Those that see no-tillage as the
ultimate goal and regard tillage or minimum
tillage as having been only interim
learning steps (albeit practised for centuries)
will take a different view. They will
seek to maximize biological performance,
almost regardless of cost, weight and width,
and readily add the changes needed to
their management practices. The world is
full of people with both of these outlooks
and is not likely to change in this respect.
The design and desirability of an
operating width include a number of functions
beyond that of the associated opener:
power available, field topography, amount
of product to be carried and field-to-field
transport, to list a few. Each added function
integrates into the overall design and machine
width. Example machines shown in
Figs 13.1 to 13.4 have a range of widths
from 4 to 18 m, all outfitted with the same
inverted-T opener but with widely varied
configurations.
Surface Smoothing
The opportunity to smooth the ground prior
to drilling is lost under a no-tillage regime.
Thus, the drill or planter openers need to
be able to faithfully follow significant
changes in the surface of the soil without
186 C.J. Baker
detriment to drilling depths or functions.
This is a demanding requirement (see
Chapter 8), but for general drill or planter
design it places limitations on overall
machine width and design considerations.
Six metres (20 feet) seems to be about
the upper limit a machine can be expected
to span in a single frame and allow the
openers to rise and fall sufficiently to follow
each hump and hollow. Even then,
unless the openers are pushed in with a
downforce device capable of exerting consistent
force as the openers move vertically
approximately 0.4 metre (16 inches), some
Large-scale Machine Design 187
Fig. 13.1. A 4.5 metre wide rigid-frame end-wheel no-tillage drill.
Fig. 13.2. A 12 metre trailed toolbar with folding wings for transport.
inconsistent seeding depth will result from
a 6 metre wide drill or planter. Where
widths greater than this are required, multiple
units or folding wings from a central
unit should be considered. Even a 6 metre
width with good opener surface-following
ability is feasible only on reasonably flat
ground. A more universal size would be
4.5 metres.
Nor does it make any difference
whether the openers are spaced 150 mm
apart or up to 1 metre apart. Each individual
opener must rise and fall in response
to surface irregularities independently of
188 C.J. Baker
Fig. 13.3. A 4 metre rigid toolbar that is lifted clear of the ground for transport.
Fig. 13.4. An 18 metre toolbar that is end-towed for transport.
its neighbours. Its inability to do so will
result in a missed row, regardless of how
many other rows there are.
Because the micro-contour of the
ground surface remains undisturbed, the
gauge/press wheels of no-tillage openers
must operate on a rougher surface than
with tillage. Cushioning of this roughness
can be achieved by springing the gauge/
press wheels, but this virtually eliminates
their gauging (or depth-control) function,
since the relationship between the position
of the wheels and the base of the slot (position
of the seed) constantly changes when
gauge wheels are sprung. Alternatively,
mounting the wheels on walking beams
effectively halves the magnitude of each
surface irregularity, which will smooth the
passage of an opener equipped with rigid
or semi-pneumatic gauge wheels, without
compromising their gauging function.
Then there is the question of speed.
Obviously the faster the drill or planter is
pulled, the rougher will be the ride. This is
especially important with planters, because
the accuracy of seed selection and final
spacing is affected by the smoothness of
ride. A speed that is acceptable for operating
a given precision seeder on tilled soil
may well be too fast when the same seeder
is operated on untilled soil. This is a negative
factor as far as no-tillage is concerned
but must be balanced against the fact
that several passes with tillage tools would
have been necessary before planting was
even attempted into a tilled soil. Therefore,
if a slower planting speed is necessary for
no-tillage planting, it will only reduce, not
reverse, the advantages associated with
no-tillage. And, with drilling of small seeds
compared with precision planting of larger
seeds, there are almost no speed restrictions.
Indeed, some no-tillage drills operate at
faster speeds than their tillage counterparts.
Power Requirements
No-tillage drills and planters require more
power to pull them through untilled soils
than do their tillage counterparts. This is
partly due to the fact that the openers are
designed to break untilled ground and
partly because the machines are heavier.
Typical power requirements are 3 to 9 tractor
engine kilowatts (kW) (4 to 12 horsepower
(hp)) per opener (see later in this
chapter). This amount of power also
requires an associated traction increase;
thus four-wheel-drive and tracked tractors
are used more with no-tillage drills than
with drills used in tilled seedbeds.
This power requirement places constraints
on the number of openers that can
be pulled with any given tractor. For example,
a 25-opener drill operating on flat, light
soil might require a tractor engine of
approximately 150 kW (200 hp), while the
same drill operating on silty and/or hilly
soils or in dense sod might require a tractor
with 50% more power.
Power requirements are also related to
drilling speed. Some openers can operate
satisfactorily at relatively high speeds (up
to 16 km/h). Others should not be used
above 7 km/h. The tractor power requirement
will increase at higher speeds, but this
will be put to good use by covering the field
more rapidly.
Planters gain an advantage over drills
with respect to tractor power requirement.
The smaller number of openers on planters,
due to their wider row spacing of up to
1 metre, means that tractor size will seldom
be the limiting factor to machine size. Generally,
it will be the surface-following
ability of the openers that will dictate the
upper limit of planter size, whereas with
drills available tractor power is often the
limiting factor. As a rough guide, for any
given width of operation, a planter will
require half the tractor engine power of a
similar-sized drill.
Finally, drill width will be determined
by a combination of opener number and
row spacing. In general, crops benefit from
closer row spacing under no-tillage than
under tillage because of the improved moisture
availability of untilled soils. On the
other hand, the physical limitations imposed
by residue handling dictate that notillage
rows are seldom spaced less than
150 mm apart on drills.
Large-scale Machine Design 189
Weight and Opener Forces
Each design of no-tillage opener requires a
different downforce to obtain its target seeding
depth. Required downforce is determined
by a number of variables:
1. Soil strength, which determines the
soil’s resistance to penetration.
2. Soil moisture and density, which affect
soil strength.
3. The presence or absence of stones and
their sizes.
4. The presence or absence of plant roots
that directly resist penetration.
5. The decay stage of plant roots, which is
affected by the interval between spraying or
harvest and drilling.
6. Operating speed, because openers penetrate
better at slower speeds than at higher
speeds.
7. The draught of the openers (their resistance
to moving through the soil).
8. The attachment geometry of the openers
to the drill frame, because, as an opener
moves downwards into a hollow, the vertical
component of pull increases, acting
upwards, opposing and reducing the downforce
pushing the openers into the soil.
Mai (1978) measured both the downforces
and the draught forces, at 38 mm
seeding depth at very slow speeds, of vertical
triple disc and simple winged no-tillage
openers operating in sprayed turf in a silt
loam soil at two moisture contents. The
results are shown in Table 13.1.
Data of Table 13.1 show that, while the
vertical triple disc opener required about
four times as much force to penetrate to
38 mm depth as the simple winged opener,
it required 50% less force to pull it through
the soil. The penetration action of the triple
disc opener is one of wedging the soil sideways
and downwards, accounting for its
high downforce requirement. The winged
opener, on the other hand, tends to heave
the soil upwards, reducing its penetration
force. In fact, soil acting on the upper surfaces
of the inclined wings tends to draw
that portion of the winged opener into
the ground, although this is more than
countered by the resistance to penetration
of the pre-disc, the vertical shank portion of
the opener and the lower frontal edges of
the wings.
The vertical triple disc opener is comprised
entirely of rolling discs. Once it has
attained operating depth, the forces
required to pull it through the soil are
smaller than with the winged opener,
which cuts roots and shatters a wider zone
of soil than the triple disc opener as it
moves forward. This is reflected in the
downforce : draught ratios for the two openers,
which averaged 0.65 for the vertical
triple disc opener and 0.11 for the simple
winged opener.
Not surprisingly, the wetter soil required
less downforce and draught force from
both openers than the drier soil, but the
downforce : draught ratios remained reasonably
consistent, regardless of soil moisture
content.
190 C.J. Baker
Vertical triple disc openera Simple winged openerb
Moisture content (g/g) 23% 28% 23% 28%
Downforce (N) 882 842 221 203
Draught (N) 1684 1210 2096 1852
Downforce : draught ratio 0.53 0.70 0.11 0.11
Conversion: N (newton) = 0.2 lb force.
aThe vertical triple disc opener had a flat 3 mm thick pre-disc of 200 mm diameter; the double discs were
3 mm thick and 250 mm in diameter.
bThe simple winged opener had a flat 3 mm thick pre-disc of 200 mm diameter; the wings of the tine
measured 40 mm across.
Table 13.1. Downforce and draught requirements of two no-tillage openers.
Baker (1976a), in three separate experiments,
measured the downforces required
for 38 mm penetration by a range of openers
into a dry, fine, sandy, loam soil covered
with sprayed pasture residue and at moisture
contents ranging from 14.1% to 18.2%
(g/g). The results are shown in Table 13.2.
Data of Table 13.2 show that the difference
in downforce between the vertical
triple disc and simple winged openers is
slightly less than in Table 13.1, probably
because of the softer (sandier) soil. The hoe
opener was similar to the winged opener,
suggesting that the draw-in effect of the
wings on the winged opener played only a
small role, since hoe openers do not have
wings.
The angled flat disc opener required
the least downforce of all openers tested, but
the angled dished disc opener required more
downforce than all other openers except
the vertical triple disc, possibly because of
the resistance to penetration of the convex
(back) side of the angled disc.
For a drill or planter to operate, its
weight or downward drag component must
be sufficient to provide the required combined
downforces of all its openers when
operating in the worst (usually driest) conditions
in which its openers can obtain seedling
emergence. This concept is particularly
important and often confuses would-be purchasers
of drills when faced with the claims
and counterclaims of manufacturers. For
example, vertical double or triple disc openers
are known to perform poorly in terms
of seedling emergence in dry soils (see
Chapter 6). With few exceptions, drills and
planters featuring such openers generally do
not provide sufficient downforce (weight)
for them to obtain drilling depth in dry soils.
The drills therefore often appear to be relatively
light in construction, giving the erroneous
impression that they can penetrate the
ground more easily than other drills, when
in fact the reverse is true.
Winged openers, on the other hand, can
tolerate very dry soils, in biological terms, so
their drills and planters are often built to be
heavy enough to force the openers into soils
that might otherwise be biologically hostile.
Thus, the overall weight of a drill or planter
does not necessarily reflect the penetration
requirements of its openers in any given
soil. It may, in fact, reflect more the biological
tolerance (or intolerance) of its openers
to dry soils than anything else.
But there is more to forcing openers into
the ground than just dead weight. Figure 13.5
shows four geometrically different arrangements
for attaching openers to drill frames.
The first (and simplest) arrangement is to
fix the openers rigidly to the drill frame, preventing
articulation between the two. This
gives the drill a very poor ability to follow
ground surface changes, but the downforce
provided for each opener will remain reasonably
constant and largely predictable.
The second arrangement uses a length
of heavy spring steel to: (i) introduce a separate
drag arm between the drill chassis and
the opener; and (ii) provide limited movement
between it and the drill frame. To
accomplish the second function, the upper
Large-scale Machine Design 191
Vertical
triple disca
Simple
wingedb Hoec
Angled flat
discd
Angled dished
disce
Downforce (N) 770 281 263 133 445
Conversion: 1 N (newton) = 0.2 lbs force.
aVertical triple disc design was as for Table 13.1. The value is the mean of three experiments.
bThe simple winged design was as for Table 13.1. The value is the mean of three experiments.
cThe hoe opener had a flat 3 mm thick pre-disc of 200 mm diameter, and the tine was 25 mm wide.
The value is the mean of three experiments.
dThe angled flat disc was 3 mm thick and 250 mm in diameter. The value is for a single experiment.
eThe angled dished disc was 2 mm thick and 250 mm in diameter. The value is for a single experiment.
Table 13.2. Downforce requirements of a range of no-tillage openers.
portion is extended and often coiled several
times to increase its flexibility. In operation
the soil drag on the opener tends to cause
the drag arm to pull backwards as well as
deflect upwards, but the actual displacement
in either direction is relatively small.
This means that the point of action of the
applied downforce in the soil remains relatively
constant in relation to the drill frame,
and there is therefore little change in
downforce as the openers traverse undulations
in the ground surface.
This design limits their ability to faithfully
follow variations in the ground surface.
In addition, many similar designs allow the
openers to wander sideways, with the result
that inter-row spacing varies somewhat,
although this also gives them an ability to
handle large surface stones with less blockage
than either rigid openers or drag arms
that move only in the vertical plane.
The third arrangement is commonly
used for conventional drills for tilled seedbeds
and has been simply transferred to
many no-tillage drills with adjustments
only for robustness and the magnitude of
the applied downforces. It consists of a
pivot-mounted single drag arm, which is
pushed down from above or sometimes
pulled down from beneath. The opener cannot
deflect rearwards, only upwards and
downwards in a limited arc about the pivot
point between the drag arm and the drill
frame. Because the force applied by the
tractor to create forward movement (drag
force) acts through this pivot point and is
opposed by the resistance of the opener at
the point of soil contact, these forces can be
resolved into their vertical and horizontal
components by triangulation.
Figure 13.6 shows the resulting force
diagram. The drag, or draught force applied
by the tractor is opposed by the soil resistance
to forward movement (P) through the
soil. This is shown as the horizontal component
of pull (H) in the diagram. The vertical
component of pull (V) is derived from the
resultant line of pull (R) which passes through
the point of attachment of the opener to
the drill and the centre of resistance (X) of
all soil forces, which is the point of equilibrium
of all soil resistance forces on the
opener and is located somewhere beneath
the soil. The vertical component of pull (V)
acts upwards and, together with the vertical
force arising from the soil’s resistance to
penetration, has to be overcome by the net
vertical downforce (D), which is applied
separately by springs or other means on the
drill (not the tractor) for the opener to remain
in the ground.
All of these forces find an equilibrium,
but a problem arises when the position of
the opener changes relative to the drill
frame. For example, as the opener passes
into a slight hollow and moves downwards
(relative to the pivot point or drill frame),
the horizontal component of pull (H) may
192 C.J. Baker
Fig. 13.5. The geometrical options for attachment of drag arms to a no-tillage seed drill. *Opener also
moves forward, but since the whole machine is moving forward anyway this is ignored as it does not
affect the function of the opener in any way.
not change, but the vertical component of
pull (V) will increase because the resultant
line of pull acting through the pivot point
(R) will have become steeper.
This means there will then be a greater
upward force opposing the net vertical
downforce (D) on the opener, which at best
remains constant, resulting in shallower
drilling. It would be a big enough problem if
the applied downforce did in fact remain
constant, but, where the mechanism of
downforce application on the drill is commonly
a spring, the downforce will actually
decrease somewhat as the opener moves
downwards because the spring lengthens.
The net effect is a significant reduction in
the net vertical downforce (D) applied to
the opener, resulting in shallower drilling
for that portion of the field.
The opposite effect occurs when an
opener passes over a hump. Characteristically,
openers with this common geometrical
arrangement drill ‘hollows’ too shallowly and
‘humps’ too deeply.
However, the problem does not stop
there. If the soil resistance to forward movement
(P) increases because the drill encounters
an area of harder soil, the magnitude of
the resultant line of pull (R) will increase,
even though its slope may remain the
same. This in turn will increase the vertical
component of pull (V), which, unless it is
compensated for by an increase in net
vertical downforce (D), will also result in
shallower drilling.
In reality, both the soil surface and resistance
to forward movement of individual
openers continually change under no-tillage.
Therefore, so too does the vertical component
of pull, causing penetration variation.
The fourth arrangement (Fig. 13.5) is
common on precision planters and more
sophisticated no-tillage drill designs. Here
the single pivoting drag arm used in the
third arrangement is replaced by two parallel
drag arms of equal length arranged as a
parallelogram, illustrated on the right of
Fig. 13.5. The objectives of this configuration
are fourfold:
1. To maintain a predictable relationship
between several components on an opener
assembly. Some planter openers, for example,
have up to six separate components following
one another in a fixed relationship.
If the assembly were mounted on a single
pivot drag arm (Figs 13.5 and 13.6) and
moved in an arc as it rose and fell, the vertical
relationship between the forward and
rear components would alter appreciably as
it travelled vertically.
2. To maintain a given approach angle of
critical components to the soil, regardless of
the vertical position of the opener assembly.
Large-scale Machine Design 193
Fig. 13.6. The distribution of forces acting on a no-tillage opener as it is pulled through the soil.
Winged openers, for example, have soil
wings that slope downwards towards the
front at an angle of 5–7° to the horizontal so
that they can operate at shallow depths
with the wings still beneath the ground. If
the opener were mounted on a single-pivot
drag arm, the preset wing angle would need
to be increased to about 10° to ensure that a
positive wing angle remained at the bottom
of the arc of movement. But in the midposition
an angle of 10° would limit the
shallowness of drilling because the wings
would break through the surface of the soil.
3. To reduce the magnitude of the forces
opposing the downforce. Although a parallelogram
arrangement will have little or no
beneficial effect on the vertical component
of pull opposing the downforce, there is yet
another force that also opposes the downforce
on single-pivot drag arms. This is the
rotational force arising from the horizontal
soil drag acting rearwards on the base of the
opener (which is always positioned lower
than the pivot itself). With a single-pivot
drag arm arrangement, this rotational force
causes the opener to attempt to rotate
upwards, regardless of the opener position
or angle of the drag arm, and opposes the
downforce. The actual magnitude of this
opposing force is somewhat self-cancelling
because, if the opener rotated upwards, the
soil drag would then be reduced because
the opener would be drilling more shallowly.
On the other hand, when the arms
are horizontal in a parallelogram arrangement,
this rotational force is eliminated
altogether and has no effect on the downforce.
Most drills and planters are designed
so that the drag arms are nearly horizontal
in the normal drilling position.
4. To facilitate the design of long and
short drag arms without changing the position
or geometry of the downforce application.
The force mechanics of parallelograms
is such that, if a downforce is applied
part-way along one of the horizontal arms,
there will be a resulting vertical downforce
at the rear pivots. Further, if a rigid horizontal
frame is attached to these rear pivots,
the same downforce will be applied at any
point along this rigid frame. Since an
opener attached to the rear pivots of a
parallelogram acts as a rigid horizontal
frame, this principle applies to openers
mounted on parallelogram arms.
In drill designs, this allows openers of
difference lengths to be attached to parallelogram
linkages in order to create stagger for
residue-clearance purposes, and each opener
will experience the same downforce as its
neighbour.
Although the best of the innovations
and geometric arrangements discussed above
go a long way towards ensuring that notillage
openers receive constant downforces
throughout their extended ranges of travel, it
should be emphasized that the magnitude
and direction of the main opposing forces
(i.e. the upward vertical components of pull
and soil resistance) vary with soil conditions
and the position of the opener at any
one point in time and are therefore seldom
constant. Thus, no geometrical arrangement
so far devised has the ability to maintain a
truly consistent net penetration downforce
on an opener.
Re-establishing Downforce
An adjunct to the general downforce requirements
of no-tillage drills and planters is
the range of methods used to ensure that a
drill or planter re-establishes the downforce
to its preselected level after the openers
have been raised from the ground for transportation
and/or cornering. Repetitive raising
and lowering of the openers are more
common in no-tillage than in tillage because
turning sharp corners with the openers
engaged is difficult in untilled ground. Some
of the systems used are:
1. Manual return to a guide mark. Where a
drill or planter is designed to raise the
openers using one or more hydraulic rams
on the machine frame, the resetting of those
rams to their original positions is achieved
by the operator watching a guide mark to
indicate where the ram(s) had extended or
contracted to previously and stopping the
cycle at that point. The potential exists for
operators to forget to watch the guide mark
194 C.J. Baker
and, in any case, such a repetitive manual
task adds to operator fatigue. On the other
hand, this system allows the downforce on
all openers to be altered by the operator
without leaving the tractor seat.
If a drill or planter is three-point linkagemounted
to the tractor or has a separately
controlled set of transport wheels, the
depth adjustment is usually achieved by
changing a mechanical linkage, a screw of
some description, or the pressure in a second
independent hydraulic system. This
adjustment remains unaltered during drilling
and transportation cycling. Return of
the machine to the ground after transportation
automatically re-establishes the magnitude
of the original downforce, since nothing
will have been altered in that respect during
transportation. While this reduces operator
fatigue, alterations to the downforce often
require the operator to leave the tractor.
2. Return to an automated stop or pressure.
Where a drill or planter is designed to
raise and lower its openers hydraulically,
an adjustable hydraulic or mechanical control
valve can be positioned on the machine
so that a predetermined mechanical movement
or oil pressure build-up will trip the
valve and halt the hydraulic system at any
desired position commensurate with a
given downforce. While this increases convenience
for the operator, a time delay still
results while the tractor hydraulic system
moves the ram to its predetermined position,
and alterations to the magnitude of the
downforce still require the operator to dismount
from the tractor.
One tractor manufacturer for many
years provided a pressure-modulating system
on the internal hydraulic source within
their tractors. This system allowed the operator
to vary the hydraulic pressure from the
tractor seat, useful for pressurizing rams on
drills or planters. Repeatability of the system
simply relied on the setting of a stop on
the tractor’s hydraulic controls. The operator
returned the lever to this position after
actuating the lifting and transport cycles of
the hydraulic system.
3. Automated return. A hydraulic ‘memory
valve’ is supplied on some no-tillage
drills and planters that utilize the same
hydraulic rams for both downforce and
lifting. The memory valve increases the
repeatability of settings during frequent
transportation and drilling cycling by
automatically storing the downforce oil
pressure in the oil-over-gas nitrogen accumulator(
s) when the lifting (transport) cycle
is actuated. Upon return of the openers to
the ground, the memory valve automatically
and instantly returns the original oil
pressure to the downforce system without
further attention from the operator. This
greatly increases the speed of cycling from
drilling to transport modes, and vice versa,
which is important for field efficiency,
operator fatigue and operator accuracy.
The operating down-pressure can be changed
at any time from the tractor seat.
One of the major problems with all
no-tillage drills is that the magnitude of the
forces involved for downforce and draught
places unusually high stress loadings on
drag arms, openers and their supports. This
problem is exacerbated when drills or planters
are required to operate around corners.
The more durable designs have used ball or
roller bearings in the drag-arm pivots,
where simple bushings would usually have
sufficed for the same function with conventional
drills in tilled soils.
Unfortunately, some of the previously
used simple designs of conventional drills
have also been extended to less expensive
no-tillage drills. These units often experience
early failure of components and loss of
accuracy. For example, as pivots of drag
arms become prematurely worn, openers
are difficult to maintain in vertical or tracking
alignment, resulting in inaccurate depth
of seeding and uneven row spacing. The frequency
of breakages increases and residue
handling often suffers. These machine failures
cause frustration for the operators and
result in a decline of enthusiasm for notillage
farming.
Wheel and Towing Configurations
A major distinguishing feature of no-tillage
soils compared with tilled soils is their
Large-scale Machine Design 195
long-term ability to sustain wheel traffic
without compaction damage and their resistance
to surface damage from the scuffing
caused by machinery wheels and tracks.
Even when compaction does occur, as the
populations of soil fauna and bacteria return
to sustainable levels in response to decreased
tillage disruption and increased organic matter,
the natural restorative processes of living
soils soon ameliorate most problems.
No-tillage drills and, to a lesser extent,
planters are inherently heavier than their
tillage counterparts, but it is seldom necessary
to increase the footprint area of their
wheels, tyres or skids on a proportional
basis to their weight because of the increased
load-bearing strength of the soils on which
they operate. None the less, there is little
point in subjecting even untilled soils to
footprint pressures from drills that are significantly
in excess of the tyres on the tractors
that pull them. Tractor tyres usually
exert footprint pressures in the range of
50–85 kPa (7–12 psi) and tracks in the
30–50 kPa (4–7 psi) range.
As with conventional drills and planters,
there are several optional wheel configurations.
Some of these, with their attributes
and limitations, are outlined below.
End wheels
End-wheel designs, as the name suggests,
have wheels positioned at either end of the
drill or planter chassis. Some planters,
because of their wide row spacing, have the
wheels positioned between the rows some
distance from the ends of the machines.
This reduces side forces during cornering
and allows two or more such machines to be
conveniently joined together end to end.
End-wheel designs are suitable for
machines up to 6 metres in width. The
end wheels provide excellent manoeuvrability
and stability on hillsides and are usually
less expensive than other options. Most
designs use single wheels on each end of
the machine, making them unsuitable
for end-towing for road transportation without
the addition of special transport
wheels. Some designs use paired wheels on
walking beams, which double the footprint
area, reduce bounce and provide an opportunity
for convenient conversion to end-towing.
End-wheel drills and planters are not
well suited to the joining of several units
together side by side. Where joining machines
is contemplated, it is necessary to arrange
the multiple units in an offset pattern
from a common and separate towing frame
(as illustrated in Fig. 13.7). On the other
hand, no-tillage farming saves so much
time that had been previously devoted to
tillage before drilling that the need for wide,
multiple drills and planters is reduced
considerably.
Fore-and-aft wheels
Fore-and-aft wheel configurations involve
one or more self-steering wheels on either
the front or rear of the machine and at least
two fixed wheels on the opposite end. The
configuration reduces the lateral distance
between the wheel positions, permitting
wider machines to be designed than with
end wheels. Because there are no wheel
structures on the ends of the machines,
multiple units can be conveniently joined,
as illustrated in Fig. 13.8. Such multiple
arrangements need a much less complicated
common towing facility than do multiple
end-wheel arrangements.
Another arrangement permits two drill
units to be used either as a narrow-row drill
or as a wide-row planter. The row spacing
of each unit is fixed to the desired spacing
for the wide-row planter configuration and
two such units are arranged end to end to
produce a double-width planter (see
Fig. 13.9). When narrow-row drilling is
required, the two units are arranged in tandem
fashion, with the rows of the rear unit
splitting the rows of the front unit, thus
halving the row spacing.
Of course, for this convenient arrangement
to be functional, the seed metering
mechanisms must be capable of sufficient
accuracy to satisfy the needs of both the
planter and the drill. Very few seeders are
capable of this degree of flexibility. Either
duplicate seeders are used (which is
196 C.J. Baker
Large-scale Machine Design 197
Fig. 13.7. End-wheel drills
arranged in an offset multiple
arrangement.
Fig. 13.8. Fore-and-aft wheel
drills arranged for multiple unit
operation.
expensive and mechanically complicated)
or one or the other of the two seed metering
functions is compromised.
The options for transportation conversions
with fore-and-aft wheel configurations
are many and varied. An example of a
convenient arrangement for a three-unit
ganged drill is shown in Fig. 13.10. The two
outer drill units fold forwards after the
whole machine is raised clear of the ground
for transportation. Other options include
folding the outer units upwards, but this
option is limited to air seeders and planters
with lockable lids on their product hoppers
to avoid spillage. The product hoppers
on air seeders are located on the central
drill unit and not involved in the folding
process.
Yet another arrangement for transporting
two fore-and-aft wheel drills is shown
in Fig. 13.11.
Matching Tractors to Drills and
Planters
In conventional tillage, tractors are usually
selected to match the heaviest powerdemanding
implement(s) used, from primary
tillage (usually ploughing) to drilling. Since
drills and planters in conventional tillage
are among the least power-demanding
implements, tractors are seldom selected to
match drills and planters, or vice versa.
Indeed, often a smaller available tractor
than the main tillage tractor(s) is used for
drilling and/or planting.
In no-tillage farming, the sprayer is the
only light power-demanding implement
in the system. Drills and planters are the
heaviest power-demanding implements,
and this power requirement may exceed the
power required by any one of the tillage
implements it replaces. This is not to say
that no-tillage is energy-inefficient. On the
contrary, this single input of energy is
several times more energy-efficient in terms
of total litres of tractor fuel used per sown
hectare than the sum of all of the multiple
smaller inputs of energy during tillage.
With planters, the maximum number of
widely spaced rows to be sown by any one
machine seldom exceeds 12. The power
requirement for such machines is therefore
less likely to be a limiting factor, even
under no-tillage, than with no-tillage drills,
which may have up to 50 such openers.
198 C.J. Baker
Fig. 13.9. Two-wide row units arranged in tandem to produce a drill with half-row spacing.
First-time no-tillage farmers must often
change their evaluations to correctly match
tractors with drills and planters. Difficulties
arise in several ways:
1. Farmers are not used to thinking of
drills in terms of their power requirements.
2. There is little information available to
inform farmers about the specific power
Large-scale Machine Design 199
Fig. 13.10. A folding arrangement for multiple drills.
Fig. 13.11. A towing
arrangement for two
fore-and-aft wheel drills.
and/or draught requirements of different
drills and/or openers.
3. Because no-tillage drills are often considerably
heavier than their tillage counterparts,
some of the power requirements will
be needed to move the machine weight,
especially on hilly land.
4. Since no-tillage drills and planters
break untilled and often hard ground, they
are more sensitive to speed than tillage
drills as far as power demand is concerned.
5. On the other hand, because no-tillage is
so much more time-efficient than tillage,
high drilling/planting speeds may not be
important.
6. Often, in no-tillage, the traction of a
tractor will be more important than its available
engine power. Thus, four-wheel-drive
and tracked tractors are likely to become
more useful.
7. Because turning corners while drilling
with no-tillage drills is more difficult than
with tillage drills, more fields are drilled in
strips (‘lands’). This demands sharp turning
on headlands or looped turns on corners,
requiring a tight turning-circle capability
from the tractor and drill.
8. The annual tractor use for drilling/
planting is likely to be reduced substantially
under no-tillage compared with tillage.
This means that total annual tractor
costs are lower, tractors last longer in terms
of time and replacement scheduling, but
the actual hourly cost may be increased.
9. The necessity to continuously monitor
drill/planter functions from the tractor
seat is increased, because under no-tillage a
farmer has but one chance to get everything
correct. Tractors therefore need to be electronically
as well as mechanically compatible
with their drills and planters.
10. The soil in wheel tracks under notillage
is often loosened because of the high
demand for traction, whereas under tillage
the result is almost invariably compaction
in the wheel tracks. Tractors working near
the traction limit in no-tillage will cause
more soil loosening and therefore greater
differences of opener performances between
those within and outside the wheel
track areas.
It is difficult to generalize power requirements
of no-tillage drills because they have
a large range of weight and draught.
Ignoring the weight of the drill, some generalizations
can be made about the power requirements
of individual no-tillage openers
from Table 13.1. While draught requirements
for only two openers (triple disc and winged)
are shown, these two designs are near either
end of the range of draught requirements for
no-tillage openers. Thus, their requirements
may reflect a range of power requirements for
no-tillage openers in general.
The power required to pull an opener
through the soil is given by the expression:
power (kW) =
pull (newtons) speed (km/h)
3600
×
or
power (hp) =
pull (pounds) speed (miles/ h)
375
×
It can be seen in Table 13.1 that at a
speed of 5 km/h (3 mph) a single triple disc
opener would require up to 2.3 kW (3 hp) and
a single simple winged opener up to 2.9 kW
(3.8 hp). At 10 km/h (6 mph) the respective
power requirements would be 4.6 kW (6 hp)
and 5.8 kW (7.6 hp).
In general, the power requirements of
no-tillage drills and planters might range
between 2 and 6 kW (2.5 and 8 hp) per
opener, depending on the drilling speed, the
ground conditions, the soil type, the density
and state of decay of root material in the soil,
the contour of the field, the method of working
the field, the design of the opener and
the weight of the machine. Allowing for a
tractive efficiency of 65% by the tractor, this
would require a tractor engine size range
from 3 to 9 kW (4 to 12 hp) per opener, which
closely matches field experience.
Product Storage and Metering
For handling products such as seed, fertilizer
and insecticides, the most distinguishing
feature of no-tillage drills in comparison
with their tillage counterparts arises from
200 C.J. Baker
the need for openers to be spaced widely
apart to clear surface residues. With planters,
the openers are spaced widely apart,
usually in a single line, anyway. So no major
distinction is made in this regard between
planters for tillage and for no-tillage.
With drills, the wider-than-normal
opener spacing is usually achieved by
increasing the longitudinal staggering of
alternate openers, since the row spacing
between openers cannot be altered without
affecting the agronomy of the crop. This
increase in longitudinal spacing results in
long seed delivery tubes and shallow drop
angles between the hoppers and openers for
these tubes if supplied by a single hopper.
Such shallow angles interrupt normal gravity
flow, especially on hilly land. The problem
is overcome in one of three ways:
1. Raising the product hoppers to greater
heights above the openers so as to increase
the angles on the delivery tubes (Fig. 13.12).
2. Doubling the number of hoppers so
that each hopper is positioned over the
openers at normal height and delivery tube
angles.
3. Utilizing air delivery of product to the
openers from a central hopper (Fig. 8.14).
There are arguments for and against
each option. Doubling the number of hoppers,
for example, adds to the capital cost of
the drill but increases the amount of
product that can be carried and therefore
reduces the number of times the machine
needs to be out of service for filling, as well
as temporarily adding to the weight of the
machine, which may help with downforce.
Air seeders are inexpensive but larger
designs carry the weight of the product on a
separate axle where neither it nor the
weight of the hoppers themselves contributes
to the overall weight of the machine
to assist downforce.
High hoppers are inexpensive but are
difficult to fill and contribute to drill instability
on hillsides. On very steep hills, at
least one drill that carried liquid fertilizer
tanks provided a facility to slide the tank to
the uphill side of the drill to assist stability
(Fig. 13.13). There are no known designs
that shift dry hoppers on the move.
Because the surface residues common
in no-tillage provide a habitat for pests (and
their predators), it is often necessary to
apply insecticide(s) with the seed at drilling.
Thus, dry granule hoppers and/or
liquid insecticide facilities are common on
Large-scale Machine Design 201
Fig. 13.12. A no-tillage drill with elevated product hoppers.
some no-tillage drills and planters. Some
planter manufacturers have cooperated
with chemical manufacturers to provide
closed transfer systems for insecticides.
This provides for safer handling of chemicals,
although operators need to be cautious
of pesticide residues on drill and planter
components during maintenance.
The concept of drilling and spraying
simultaneously by mounting a spray boom
on the drill or planter was investigated in
New Zealand. While such an achievement
would have made no-tillage a truly onepass
operation, the idea was judged not
practical for several reasons:
1. It was possible to drill on days on which
it was not wise, or possible, to spray because
of wind or rain that might otherwise compromise
the efficacy of weed and pest control
formulations. By restricting drilling opportunities
to those times when spraying was
possible, some of the time advantage of
no-tillage would have been lost.
2. It introduced yet another function to be
observed by the operator and/or monitored,
increasing the potential for error.
3. Some openers displace, or indeed
throw, soil, causing dust, which inactivates
the most commonly used herbicides in
no-tillage (glyphosate and paraquat). Spraying
is better performed with a separate
operation by a specialist prior to drilling.
Although blanket application of herbicides
at the time of drilling appears to be
impractical, banded application on each row
has been used successfully (see Chapter 12).
Summary of No-tillage Drill and
Planter Design – Large-scale
Machines
1. Designs of no-tillage drills need to be
more sophisticated than those of tillage
drills.
2. No-tillage drills are invariably heavier
than tillage drills and are more stressed
during operation.
3. Wear and general maintenance are
more important and expensive on no-tillage
drills and planters than on tillage drills and
planters.
4. The tractor engine power required to
operate no-tillage drills and planters ranges
from 3 to 9 kilowatts (4 to 12 horsepower)
per opener.
202 C.J. Baker
Fig. 13.13. A no-tillage drill with sliding liquid fertilizer tank.
5. The power requirements for no-tillage
drills and planters are more sensitive to
operating speed than those for tillage drills
and planters.
6. Larger tractors are generally required
for no-tillage drilling.
7. Because tractors are operated fewer
hours per year than tillage tractors, their
hourly operating costs are higher than the
latter but their total annual costs are
reduced.
8. The total energy expended per sown
hectare and the annual operating cost of all
equipment are much lower in no-tillage
than for full tillage.
9. No-tillage drills are generally narrower
than tillage drills because of the increased
power requirement. No-tillage planters
may be the same width as tillage planters
because of fewer openers.
10. Although it is not as necessary to travel
as fast during no-tillage drilling or planting
as in tillage because of the time efficiency of
the system as a whole, some no-tillage drills
and planters are actually capable of higher
speeds than their tillage counterparts. On
the other hand, other no-tillage designs
require low speeds.
11. Time analyses to cover a field with a
relatively narrow no-tillage drill compared
with a wider tillage drill often fail to
account for the multiple tillage passes made
before the tillage drill begins work.
12. Downforce systems on no-tillage drills
and planters need to be more sophisticated,
exert greater force and have a greater range
of travel than for tillage machines.
13. The geometry of no-till opener dragarm
attachments must compensate for the
increased drag forces.
14. Parallelogram drag arms with either gas
or oil-over-gas hydraulic pressurized downforce
systems provide the most consistent
downforces and seeding depths.
15. Drill and planter frames should be suspended
on wheel arrangements that minimize
bounce from uneven ground.
16. Turning corners while drilling or planting
is more difficult in no-tillage than in
tillage because of the firmer soils.
17. The firmer ground in no-tillage is better
able to withstand scuffing from the wheels
when turning corners than with tilled soils.
18. Automated systems that return the
opener downforces quickly to preselected
values after raising the openers for transport
are desirable in no-tillage because of the
need to raise the openers more frequently
during operation.
19. End-wheel drill and planter configurations
are generally the cheapest option but
have a maximum width of approximately
6 metres (20 feet).
20. Fore-and-aft wheel configurations
allow greater drilling widths and simpler
side-by-side joining of two or more drills or
planters.
21. Delivery of product from hoppers to
no-tillage openers is somewhat more
demanding than for tillage drills because of
the need for wide spacing between adjacent
no-tillage openers to clear surface residues.
22. Because both tillage and no-tillage
openers on planters are widely spaced,
there are fewer special requirements for
product delivery on no-tillage planters
compared with drills.
Large-scale Machine Design 203
14 No-tillage Drill and Planter
Design – Small-scale Machines
Fatima Ribeiro, Scott E. Justice, Peter R. Hobbs and C. John Baker
Small-scale no-tillage farming is not only
practical but may be the most important
improvement to crop production and
resource protection for developing nations
to be advanced this century.
Characteristics
Small-scale no-tillage is usually characterized
by small field sizes and limited availability
of energy, often also accompanied
by limited financial resources. Operation
of large-scale tractor-drawn implements is
neither practical nor possible for many
farmers on small properties. For these reasons,
most small-scale farmers use either
hand-operating jabbing devices or drills
and planters with one or two rows. Some
triple-row planters are also available but are
reasonably rare.
The limited number of rows influences
several functions, including opener design.
Some of these influences are beneficial. Others
are not. For example, many of the more
advanced opener designs discussed elsewhere
in this book require up to 12 horsepower
per opener, which is often beyond
the resources of small farmers. Also, nonsymmetrical
openers, such as angled discs,
are seldom regarded as an option on singlerow
machines because the side forces are
too difficult to counteract while keeping the
machine heading in a straight line.
But small-scale no-tillage is benefited
by the operator attention to each square
metre being planted, and weeds and residues
are often manipulated by hand or collected
for heating fuel or animal bedding.
Another benefit is that most small-scale
planters sow fertilizer and seed simultaneously
in separate slots. In this way they
may be considerably more sophisticated than
many of their larger counterparts, some of
which do not sow fertilizer at all under
no-tillage because of the mechanical complexity
of achieving such a desirable function
with multiple rows spaced closely together.
Thus, while small-scale no-tillage might
be disadvantaged in some respects by the
necessary simplicity of drills, planters and
available power, it may also benefit in other
respects for the same reasons.
Range of Equipment
There is a wide range of small-scale no-tillage
seeding equipment available, each suited to
different sources of power and field conditions.
The range includes hand jabbing,
animal-drawn planters, power tillers and
planters for limited-powered tractors. Despite
the differences in power requirements, the
© FAO and CAB International 2007. No-tillage Seeding and Conservation
204 Agriculture, 2nd edn. (eds C.J. Baker and K.E. Saxton)
designers of most small machines recognize
the need to be able to handle residues, open
an appropriate slot, meter seed and perhaps
fertilizer, distribute this to the opener(s),
place it in the soil in an acceptable pattern,
and cover and pack the seed and the
fertilizer.
Hand-jab planters (dibblers)
Hand-jab planters are popular amongst
small-scale farmers. Some form the primary
means of sowing seeds under no-tillage.
Others are kept in reserve for filling in
spaces in crops otherwise sown with openers
in rows. Since the residue-handling
ability of small drills and planters is often
limited, spaces occur if and when residue
handling suffers along the row.
Hand jabbers may have either separate
hoppers for seed and fertilizer or one hopper
for seed only. Figure 14.1 illustrates a
typical double-hopper jab planter.
A common seed metering device used
on hand jabbers is a rectangular plate
placed inside the hopper. When the handles
are pulled apart, the seeds drop into the
holes, which are delivered to the outlet and
the discharge tube. Plates with different
hole sizes are available according to the
seed size. Seeding rates can be adjusted
according to the number of holes in the seed
plate that are exposed in the outlet.
Part of the attraction of hand-jab planters
is that they do not require access to animal
or tractor power and they are low-cost,
light and easy to operate, although some
skill is required (Ribeiro, 2004). For these
reasons they are often used by women,
which increases the available labour pool
for small farmers, although no-tillage itself
reduces labour demands significantly anyway.
By planting seeds in pockets, there is
minimal soil disturbance so weed seed germination
is minimized, resulting in easy
hand hoeing between plants. The small size
of the devices makes them suitable for operation
on hilly, stony and stumpy areas and
for intercropping (e.g. sowing mucuna
between maize rows) and for planting in
fallow areas.
Their use is most suited to light soils
since penetration is sometimes too difficult
in harder soils in the absence of some form
of tillage. Some clay soils may also stick to
the blades when working in wet conditions
and seed coverage may be affected by the
V-shaped pockets and minimal disturbance
(Ribeiro, 2004). This limitation is common
to that experienced with V-shaped continuous
slots and is not restricted to discrete
pockets. But during the transitional phase
from conventional tillage to no-tillage it
may be difficult to use a hand-jab planter, in
which case a ripper may be used to loosen a
narrow strip where the hand-jab planter
will place the seeds.
Small-scale Machine Design 205
Fig. 14.1. A hand-jab planter with seed and
fertilizer hoppers.
Many hand-jab planters for no-tillage
are adaptations of similar devices designed
for use in tilled soils. The main modification
has been to provide longer and narrower
points to improve penetration. Such
improvements require less downward force
from the operator and help to cut residues
and penetrate the soil, resulting in lessopen
slots. They have resulted in 28% and
23.6% increases in emergence of maize and
cowpeas seedlings, respectively, compared
with shorter points operating in heavy
residues (Almeida, 1993).
Row-type planters (animal-drawn and
tractor-mounted)
The principles of operation of animal-drawn
and tractor-mounted small no-tillage planters
are the same as for larger machines.
Some of these features are discussed below
and comparisons drawn between small and
large machines in terms of the conditions
under which they each operate.
Downforce
With small machines, an opportunity exists
to use weights as the method of downforce.
Springs are also used but hydraulic downforce
systems are very rare. But weights
have the same advantages as hydraulic systems
at a much lower cost. In its simplest
and cheapest form, weight can be applied
by an operator standing on a platform on the
machine. Figure 14.2 shows such a singlerow
machine directly mounted on a small
tractor. The advantage is that the weight is
easily applied and removed by simply stepping
on and off the operator’s platform.
Since weights apply a consistent downforce
regardless of the vertical position of
the opener, they act in a similar manner to
oil-over-gas hydraulic systems applied to
individual rams on each opener, which are
a feature of some of the most advanced
larger no-tillage drills.
Therefore, some small-scale no-tillage
drills and planters may provide a more
sophisticated downforce system than some
of the less-advanced larger machines. The
electronic modulation of downforce in
response to ground hardness is not possible
on the smaller machines. But, then again,
nor is the direct application of weights a
practical option for larger machines. Operators
would need to be adding and removing
multiple weights every time the downforce
206 F. Ribeiro et al.
Fig. 14.2. A tractor-mounted single-row drill that relies on the weight of an operator for penetration.
was changed. Doing so might be acceptable
on a single-row machine but would soon
fall out of favour on a multi-row machine.
Figure 14.3 shows the main components
of typical small-scale no-tillage
planters. The disc (1) cuts straw (although
the effectiveness of cutting straw in this
manner often leaves much to be desired –
see Chapter 10). Metering devices are positioned
at the bases of the seed (2) and
fertilizer (3) hoppers. The openers (4 and 5)
open slots for placement of fertilizer and
seed, respectively. Usually the fertilizer
opener (4) operates deeper or off-line compared
with the seed opener (5), in the same
manner as bigger machines. The packing
wheel (6) controls the depth of seeding and
firms the soil over the slot. The effectiveness
of packer wheels operating on the soil
over the slot, compared with operating in
the base of the slot before covering, is discussed
in Chapter 6. In general, the value of
packer wheels operating in the manner
shown in Fig. 14.3 is more one of covering
(which is important enough) than of
improving seed-to-soil contact.
Discs
All of the principles of discs and residue
handling, discussed in Chapter 10, apply
equally to small-scale machines as they do
to large-scale machines, except that with
single-row small-scale machines there is
greater clearance around the opener for random
residues to fall away without blocking
the machine.
Most small-scale no-tillage planters have
discs, the effectiveness of which are dependent
upon the disc diameter and design (plain,
notched, wavy, flat or dished), soil conditions,
residue conditions and adjustments
provided on the planter. Ineffective residue
cutting results in clogging of straw on the
seed components, which in turn results in
problems for seed and fertilizer placement
and coverage, and even seed and/or fertilizer
metering.
Uneven straw results in hairpinning by
discs and wrapping of residues on tined
openers, although Casão and Yamaoka (1990)
claimed that the severity of blockages could
be reduced (though seldom eliminated) with
increasing distance between the disc and any
stationary tines that follow (they recommended
a minimum distance of 25 mm).
On the other hand, some of the more
successful combinations of tines and discs
have the discs in close association with the
tine. One example is shown in Fig. 14.4
(centre tine), in which a groove is created in
the leading edge of the tine especially for
the disc to operate within. Figure 4.27
shows the disc version of a winged opener
in which two tines actually rub against the
flat face of a disc.
Small-scale Machine Design 207
Fig. 14.3. The main components of typical small-scale animal-drawn and tractor-mounted
no-tillage planters.
Openers
The functions of openers for small-scale
no-tillage are no different than their functions
for larger-scale machines and are discussed
in detail in Chapters 4, 5, 6 and 7.
On small-scale planters with tined openers,
there should be independent adjustment of
the fertilizer opener so that fertilizer can be
placed deeper than the seed (Van Raij et al.,
1985). Although placing fertilizer beneath
the seed in no-tillage does not always result
in the best crop yield (see Chapter 9), with
small-scale drills and planters it is a more
realistic option than placing fertilizer
alongside the seed because the latter option
requires the fertilizer opener to be operating
in new ground, which requires more energy
than when both openers (seed and fertilizer)
operate at different depths in a common
slot. In any case, placed fertilizer
within the seed zone is far superior to surface
broadcasting causing slow crop access
and increased weed growth.
As with larger machines, there are
advantages for slots with minimal disturbance
(see Chapters 5, 10 and 13). While the
choice of opener type might depend on soil
resistance to penetration and the amount and
resistance to cutting of residues, it is no more
feasible for small-scale no-tillage farmers to
possess more than one no-tillage machine in
order to cope with varying conditions than is
the case for large-scale farmers.
Therefore, to be universally useful for
practising farmers (large or small), it is inevitable
that the choice of preferred opener
types will, over time, gravitate towards
those that function best in the widest possible
range of conditions. Tillage has as one
objective to reduce the physical variability
between different soils so that drills do not
have to cope with widely varying conditions.
But, when the tillage process is eliminated
altogether, emphasis then shifts to the
capability of no-tillage openers to cope
unaided with this variability. By definition,
this demands increasing sophistication
from the designers of no-tillage openers,
regardless of their scale of operation.
Double disc openers (V-shaped slots
with Class I cover) are commonly used on
small-scale drills and planters. The slots are
narrow at the surface and may be compacted
at their bases and sides, but are less
power-demanding than tine-disc openers
that have less compacting tendencies. With
unequal-diameter double disc openers,
because the smaller disc rotates faster than
the larger disc a degree of cutting, or ‘guillotine’,
effect is created (Fig. 4.3 – Chapter 4).
A range of tined openers is shown in
Fig. 14.4. Generally, tines require less downforce
than double disc openers, which contributes
to maintaining a uniform seeding
depth if a suitable depth-control mechanism
is included. Tines are preferred in hard
soils, although their drag force may become
excessive for the power available. And tines
are more susceptible to blockage with residues
and are unsuitable in stony areas.
None the less, most of the planters used
in small-scale agriculture have tines because
of their better penetration of hard ground
and ease of manufacture. In situations where
208 F. Ribeiro et al.
Fig. 14.4. A range of tined openers used with
animal-drawn no-tillage planters. The centre
opener has a groove cut into its leading edge, in
which the leading disc rotates.
soil crusting is a problem (such as where
cattle have trampled the soil when wet),
only tractor-mounted planters with tined
openers will break the compaction in the
soil surface, although this is often only
100 mm deep.
Seed metering devices
There continues to be debate amongst
researchers about the importance of seed
spacing along the row with row crops
such as maize (Sangoi, 1990; Rizzardi et al.,
1994). More recent evidence has shown that
uniform plant emergence along the row
may be more important than plant spacing
to reduce plant competition of smaller plants
by larger plants. But the fact remains that, if
‘perfect spacing’ has become the accepted
norm in conventionally tilled seedbeds, notillage
exponents need to match this norm in
untilled seedbeds in order to avoid introducing
an unnecessary negative factor against
no-tillage.
Seed metering devices are responsible
for governing seed rate (number of seeds/m)
and seed spacing (consistency of spacing
between seeds in the row); thus their accuracy
must be assured.
Most crops sown by small farmers are
in wide rows. Singulation of seeds is therefore
important. So emphasis is placed on
seeding mechanisms and power requirements
as priority design criteria. This contrasts
with larger no-tillage planters where
slot micro-environment, residue management
and fertilizer banding assume at least equal
importance to seed spacing and energy
requirements.
No-tillage farming in Brazil provides an
interesting comparison and contrast of smallscale
machines and tractor-drawn machines.
Both systems are practised widely in a
country that spans many climatic and socioeconomic
zones, often in relatively close
proximity to one another.
Seed metering devices used on animaldrawn
no-tillage planters in Brazil all feature
the same gravity seed plates that are
used on local tractor-mounted planters,
namely plastic or cast-iron horizontal plates.
Figure 14.5 illustrates a horizontal platetype
metering device along with several
alternative plates. Some manufacturers provide
seed plates suited to small seeds (e.g.
canola, hairy vetch, forage radish) as well as
maize and other larger seeds.
The use of such devices has been
driven by their relatively low cost, since
most singulating seeders used in countries
that do not have small-scale agriculture are
now of the vacuum, air pressure or ‘fingerpicker’
type, which involves seeds being
sucked, blown or clamped against vertical
plates rather than falling under gravity into
holes or notches in horizontal plates. Vertical
plate seeding mechanisms are faster and
less sensitive to seed shape and size than
horizontal plate-type seeders, but are also
more expensive. Of course, vacuum and air
singulators also require a powered air fan as
the basis of operation and this would be
Small-scale Machine Design 209
Fig. 14.5. A horizontal plate metering device (left) used in precision planters, with an array of optional
seed plates (right).
difficult to facilitate on an animal-drawn
machine without resorting to a stationary
engine.
Horizontal plate singulators are a very
old, well-proven and refined system that
pre-dated the vertical plate systems now in
common use on larger planters. It is no surprise,
therefore, that, when Ribeiro (2004)
evaluated the uniformity of distribution of
maize seed along the row with four models
of plate planters in Brazil, she found no significant
differences between models in the
proportion of normal spacings, skips and
doubles. The results are summarized in
Fig. 14.6.
To be most effective, horizontal plate
singulators require the seed to be graded
into uniform sizes and the holes or cups in
the plates to be matched to the chosen seed
size. This requires having several plate
sizes and some experimentation when seed
lines or batches are changed. But, with limited
numbers of rows and small quantities of
seed, this is not a difficult undertaking compared
with multi-row machines. But it does
highlight the importance of being able to
change plates without emptying the entire
seed hopper. Figure 14.7 illustrates a closed
hopper system that allows the plate to be
changed without spillage of seed.
Fertilizer metering devices
The types of fertilizer metering devices
found on small-scale no-tillage machines
210 F. Ribeiro et al.
Fig. 14.6. Percentage of normal spacings, skips and multiple seeds provided by four models of
animal-drawn no-tillage (NT) planters (Ribeiro et al., 1998). The criteria for classification of spacing is
based on Kurachi et al. (1993). Each crop has an ideal spacing (Xref), which depends upon the
recommended number of plants/m. For example, if for maize the recommendation is 7 seeds/m,
then Xref is 1.00/6 = 0.17 m. In this manner the following classes are established: normal
(Xref < Xi < 1.5 Xref); doubles (Xi > 1.5 Xref) and skips (Xi < 0.5 Xref).
Fig. 14.7. A closed hopper system for easy seed
plate change.
include rotating bottom, auger type, edge
cell and star wheels (Figure 14.8). The
discharge rate for star-wheel and rotatingbottom
types is controlled by adjustable
outlets, while auger and edge-cell types are
controlled by changing their speed of rotation
relative to the ground speed (Ribeiro
et al., 1998).
Packing wheels
While seed row packing wheels vary in
design, most are of either steel or plastic construction.
V-shaped wheels are used where
soil disturbed by tined openers needs to be
collected and thrown into the open slots.
Good coverage/compaction depends on the
depth of seed placement, the type of seed
compaction wheel and soil moisture. Opencentred
wheels are better for soils with a
tendency towards crusting as they press the
soil laterally towards the seed.
Power requirements and ease of operation
Small-planter operation requires more intimate
operator involvement than for larger
machines. Therefore ease of operation is
important. For example, most small planters
require the operator to hold a pair of
handles and steer the machine, as well as
controlling the animals that may be pulling
them. With small tractor-drawn machines, a
second operator usually controls the tractor.
In either case, energy requirements are
important. But, since the openers used on
most small planters are similar to those
used on larger machines, all of the forces
and principles of soil reaction apply equally
to both classes of machine.
Of the seven machines reviewed by
Ribeiro et al. (1998), four featured tined
seed openers and three featured double disc
openers. Ralisch et al. (1998) evaluated the
draught and energy requirements of a small
planter with tined seed and fertilizer
openers in an untilled soil of quite low bulk
density, 1.07 g/cm3, operating at 100 mm
depth. They recorded a draught force of
834 N, which is less than half the values
recorded by Baker (1976a) for a single simple
winged opener (see Chapter 13).
Draught forces vary widely with soil
strength, which is itself influenced by soil
moisture content, soil type, SOM and the
time under no-tillage. So it is difficult to
compare opener (or, indeed, drill) types in
different conditions. But, at 2.4 km/h, the
machine tested by Ralisch et al. (1998)
would require 1.4 kW of draught power or
approximately 3.6 kW (5 hp) of tractor
engine power (at a tractive efficiency of
0.65). This compares with larger drills,
which commonly require 4–9 kW (5–12 hp)
of engine power per opener to operate at up
to 16 km/h. Such high forward speeds are
unobtainable by small machines, even if
sufficient power is available, because of the
difficulty in controlling them at high speed,
especially if the operator walks behind
the machine. Therefore the lower power
requirement for small machines probably
reflects the lower operating speeds more
than other variables.
Small-scale Machine Design 211
Fig. 14.8. Two examples of fertilizer metering devices used on small-scale no-tillage planters.
Left: edge cell (or fluted roller); right: star wheel.
According to Siqueira and Casão
(2004), differences in power requirements
are primarily due to the design of the
openers, the weight of the planter and the
number, and the contact surface area of
the residue-cutting and groove-opening
components. The main characteristic that
makes such machines suitable for small
tractors or animals is the small number of
rows: two and three rows for maize and soybean
planters and six to seven rows for
wheat and rice drills.
Some of the factors that contribute to
the physical effort by the operator in controlling
the machine are the weight of
the planter, the height of the handle(s),
manoeuvrability, stability and ability to
operate on sloping ground. The height of the
handle(s) becomes particularly important
during headland manoeuvres and in most
cases is adjustable. Multiple-row models
generally require less manual effort from the
operator than single-row models, because
seats or standing platforms are provided.
Models with two rear support wheels
provide good stability when working on flat
land but may be constrained on hillsides.
Models with only one wheel are more
adapted to stony and stumpy areas because
it is easier to steer such machines around
obstacles. For those models that evolved
from ‘fuçador’ ploughs, improved stability
occurs when fixed-shaft systems are used
rather than chains. The ‘fuçador’ plough
consists of a wooden drawbar, which is
fastened to the yoke of the draught animal(
s), on which is mounted a leg and a
shovel-like plough body (Schimitz et al.,
1991). For no-tillage, the mouldboard plough
body is replaced with no-tillage openers.
The device is used in the stony and hilly
areas of south Brazil.
Adjustment and maintenance
All models offer adjustments of both seed
and fertilizer sowing rates. But some models
do not offer many adjustments either for
seed and fertilizer sowing depth or for residue
handling. On the other hand, the most
sophisticated openers do not require adjustments
to handle a wide range of residue
types, but these are seldom used on small
drills or planters. In general, tined openers
have the poorest residue handling characteristics
(see Chapter 10) and disc openers
the best. But certain disc openers (e.g.
double disc) have a tendency to hairpin
pliable straw into the slot, where it interferes
with seed germination in both wet and
dry soils. These disadvantages apply equally
to small planters as to larger equipment.
For this reason, several small planters
with tined openers provide adjustments
that affect their residue-cutting ability. The
two main adjustments are the hitching
point and the front ground wheel. Adjustments
made to the disc will also affect the
depth of the fertilizer slot. For the same
depth of the fertilizer, different depths for
seeds are possible through adjustments of
the rear ground wheel.
In the simplest models, seed rates are
adjusted by changing to different seed plates,
while multiple-row models often provide
sets of gears to change the plate speed. Other
models that do not sow widely spaced rows
provide geared adjustment of the speed of
bulk seeders.
Animal-drawn planters
Figure 14.9 shows a range of no-tillage
drills developed in Brazil. The models
shown in the two top photographs are more
sophisticated, have a greater range of
adjustments and are likely to produce better
results than the models shown in the two
middle photographs, which have evolved
from ‘fuçador’ ploughs. They are lighter,
less expensive and more adaptable to hilly
and stony areas. The model shown in the
bottom photograph features disc openers
and platforms for an operator.
Planters adapted from power tillers
Power tillers that are normally used for
conventional tillage are sometimes used for
strip tillage by eliminating some of the
powered blades to till narrow strips (20 to
200 mm wide), leaving the ground between
212 F. Ribeiro et al.
the rows (up to 500 mm wide) untilled.
Chapter 4 addresses the issues of how larger
versions of such machines have been
adapted to follow the ground surface and
Fig. 4.22 shows an example of one such
machine producing narrow strips.
Tractor-drawn planters
Small farmers also use animal-drawn or
small tractor planters requiring up to 50 hp.
The machines have the same straw-cutting
(smooth disc) and slot-forming (tine or double
disc) openers as the single-row machines
and most are capable of applying fertilizer
at seeding time.
Some models provide bulk seed and/or
fertilizer hoppers in a similar manner to
larger machines (e.g. Figs 14.10 and 14.11)
while other models are set up as multi-row
precision seeders (e.g. Fig. 14.12).
No-tillage farming in Asia
Zero-tillage (or no-tillage) has been adopted
on about 10–15% (2 million out of 13.5 millions
hectares) of the wheat planted after
rice in the rice–wheat cropping system in
India and Pakistan. Spring wheat planted in
Small-scale Machine Design 213
Fig. 14.9. A range of small-scale no-tillage planters developed in Brazil.
the winter season and, increasingly, other
winter crops, such as lentils, are being
zero-tilled. Yet the gains in soil health from
the winter season are countered by puddling
of summer rice. In addition, the vast
majority of the zero-tillage occurs in fields
where the rice residue either is removed as
fodder or fuel or is burned, because the
current low-cost zero-tillage drills have no
residue-handling capacity. In many cases,
only anchored straw remains. This leads to
a hybrid system where yields cannot and will
not be maintained due to soil degradation.
Long-term experiments in Mexico have
shown that zero-tillage without residue
retention in intensive maize–wheat systems
results in more rapid decline of yields than
where a full tillage system is retained in
which residues are buried. But the best
treatment has been no-tillage with residue
retention (Govaerts et al., 2004). This points
out the need for ‘rational residue retention’
in the humid tropics and subtropics with
heavy monsoons and sometimes triple-crop
annual intensity (K. Sayre, 2004, personal
communication).
There is currently research being initiated
and undertaken in some parts of
South Asia on direct-seeded or zero-tilled
rice (RWC website). There is little or no
214 F. Ribeiro et al.
Fig. 14.10. A small tractor-drawn no-tillage drill.
Fig. 14.11. Two small planters with bulk fertilizer hoppers and precision seeders.
prior research on how to plant zero-tilled
rice under monsoon conditions. The major
problems facing scientists and farmers are:
(i) planting time decisions influenced by
erratic onset of pre-monsoon and regular
monsoon rain and little or no assured irrigation
schedule that can otherwise keep
machinery from entering fields when they
are too wet; (ii) the enormous weed management
problems brought about by the loss of
puddle conditions in sandy soils that allow
fast infiltration and therefore reduce the
ability to control weeds by impounded
water; and (iii) the lack of drainage, especially
in the lowlands, which can submerge
and kill recently emerged seedlings. Current
experiments include zero-tillage of
transplanted rice, newly available herbicides,
rice varieties that can withstand submergence
and varieties that do well in
alternating flooded and dry conditions.
Table 14.1 summarizes the special
problems for zero-tilled rice.
Research into residue retention is progressing,
but the normal Western technologies,
such as double disc openers, are
probably too expensive, heavy and need
excessive power. Indigenous or locally made
systems, such as openers, with inverted-T,
double disc and star-wheel injector planters
are moving forward. But research suggests
that much cheaper strip-tillage systems
might provide the answer to low-cost
handling of residues, especially for wealthier
farmers. For poorer farmers, residues are
highly valued for fuel and fodder and will
probably remain so for several decades.
Two-wheeled or four-wheeled tractors?
It is a problem to learn how to apply conservation
agriculture methodologies in
the intensely poverty-stricken areas of
South Asia. Although zero-tillage drills are
becoming more available, there is a dearth
of four-wheel tractors. As a result of poverty,
many holdings are small and scattered.
Intense monsoon rains provide
large challenges to researchers, conservation
agriculture proponents and machinery
designers. Whichever system(s) become
dominant, it is likely that the majority of
small and poor farmers will not own their
own equipment but will rent from service
providers.
There have been efforts in recent years
to bring conservation agriculture to twowheeled
tractor farmers. Although the area
Small-scale Machine Design 215
Fig. 14.12. A small planter adapted from animal operation for tractor mounting.
of adoption is still small, engineers and
researchers feel they are finding attachments
to fit into this complicated socio-ecological
system.
Four-wheeled tractors
India is the largest tractor manufacturer in
the world in terms of numbers. Still today,
only 50% of tillage is mechanized in India
(perhaps 90% in the rice–wheat areas) and
less than 20% in Nepal, but greater than
70% in Bangladesh. The surprising gap
between Bangladesh and the rest of South
Asia is discussed later. Further, the Indian
government laws prohibit tractor manufacturers
from manufacturing implements
such as seed drills in order to promote local
small manufacturing.
TOOLBARS AND TOOLS. Many machine toolbars
in India and Pakistan are based on
early ‘rabi’ (winter wheat, lentil) seed drills
that were developed in the 1970s and
1980s. The manufactures of conservation
agriculture machinery have for the most
part simply strengthened the frames, bars
and shanks (Hobbs and Gupta, 2004). The
toolbars are flat (i.e. not diamond) and generally
made from two pieces of 50 mm angle
steel welded together to form a square
toolbar. Two or three bars are positioned at
fixed distances. There are various systems
for attaching the shanks to the toolbars.
Farmers are learning that an adjustable
shank length provides more adaptability
but has a tendency to swing to one side or
another if not properly tightened or if of
inferior quality.
ZERO-TILLAGE DRILLS. The current level of
enthusiasm for conservation agriculture
research and development in South Asia
was sparked by a CIMMYT (International
216 F. Ribeiro et al.
Problems Possible solutions
1. Majority of rice is rain-fed. Major problems
are erratic monsoon and therefore problems of
entering fields for seeding operations.
1. Planting needs to be done as quickly as
possible when the proper soil moisture is
reached. Once the field is too wet serious
compaction will occur.
2. Smaller, lighter machinery (two- and four-wheel
tractors) may help.
3. Farmers may want to have the option of
transplanting by hand or machine into zero-till
fields if direct seeding is impossible.
4. Move to early dry-season irrigated rice.
2. Lack of drainage and flooding kills off
emerging seedlings after a heavy downpour of
monsoon rain.
1. Permanent beds and introduction of some
drainage capability.
2. Flood-tolerant rice varieties are also possible.
3. Transplanted zero-tilled rice.
3. Problems of weed control when soils are
not kept flooded (more serious on research
stations than in farmer fields).
1. Integrated weed management will be the key,
using competitive varieties, mulching, preventing
seed set of weeds, rotation and various herbicide
strategies. Untilled seedbeds where the first flush
of weeds are allowed to germinate and then
controlled with herbicide is another strategy.
In this system, avoiding ploughing will avoid a
new flush of weeds germinating.
2. Planting of a cover crop after wheat and killing the
cover crop and weeds with herbicide before
zero-tilling rice.
Table 14.1. Problems and possible solutions for zero-tilled rice.
Centre for the Improvement of Maize and
Wheat, Mexico) programme that imported
simple inverted-T drills from New Zealand
(Baker, 1976a, b, Fig. 14.13) into Pakistan in
the early 1980s for wheat. Over a period of
time, various national and international
programmes in Pakistan and India reduced
the size and cost of the initial machines
and ‘indigenized’ them. Specifically, the
popular locally made ‘rabi’ or winter wheat
drills were strengthened and locally made
inverted-T openers attached (Hobbs and
Gupta, 2004).
Toolbar platforms and tools for zerotillage
have become as uncomplicated and
light as possible (Fig. 14.14). Nearly any
medium-sized workshop is able to produce
them. The first system to fail on locally
made tractors is the draught control system
and the second is the hydraulic lift. Many
farmers who purchase zero-tillage machines
therefore find that their three-point-hitch
hydraulic lifts soon need overhauling. So
most zero-tillage drills come with various
types of depth-control wheels. In Pakistan,
pneumatic tyres are often used, but the
cheaper Indian and Pakistani models have
metal wheels.
STRIP TILLAGE DRILLS. Much less popular than
either zero-tillage or bed planting are
strip tillage drills for four-wheeled tractors
(Fig. 14.15). These drills were developed by
Indian scientists and engineers at Punjab
Agricultural University, Ludhiana, in the
late 1980s. Typically they comprise a simple
2.2 metre PTO driven ‘rotavator’ with four
blades or six blades per strip and they come
in nine to 11 row models. Such machines
cost 50% more than zero-tillage drills. Fuel
consumption is greater than zero-tillage but
much less than conventional tillage. Farmers
remark that strip tillage helps in fields where
residue levels are too high for the simple
inverted-T zero-tillage shanks. Yields are
comparable to those of zero-tillage (Hobbs
and Gupta, 2003). Pakistan research on rotating
discs, smooth and serrated, reported that
the disc wear was high.
STAR-WHEEL (PUNCH) PLANTERS. In an attempt
to solve the problem of planting into
Small-scale Machine Design 217
Fig. 14.13. Inverted-T openers mounted on rigid shanks attached to a square hollow toolbar.
(Note that details of typical inverted-T openers can be seen in Figs 4.22, 4.23 and 4.24 – Chapter 4.)
heavy residue, star-wheel or rolling
punch planters (originally developed in
Zimbabwe) have been added to existing
zero-tillage frames (Fig. 14.16). Modifications
have been made to assist with synchronization
of seed delivery and to prevent seed
from falling outside the punch (RWC website).
Perhaps the biggest problem facing
218 F. Ribeiro et al.
Fig. 14.14. A typical zero-tillage drill on a typical Indian tractor.
Fig. 14.15. Strip tillage drill from India.
this system in South Asia is its relatively
high cost.
BED PLANTERS (RIDGE AND FURROWPLANTING).
Bed systems for wheat were originally
developed by Mexico’s Yaqui Valley farmers
to compensate for dwindling water supplies.
Irrigation water is saved by applying
it through the furrows between the beds,
which greatly enhances water conservation
and drainage. Bed-planted wheat also
allows access to the field after planting for
chemical applications and mechanical
weeding. More than 90% of Yaqui Valley
farmers have now adopted the practice
(Aquino, 1998), but they still completely
knock down the beds and reshape them for
the next crop.
Work began on bed-planted wheat in
South Asia in the mid-1990s and current
adoption is increasing (Hobbs and Gupta,
2004). The goal is to eventually have permanent
beds, especially on the dry sandy soils,
where groundwater supplies are fast receding,
or on clayey soils, where wheat is prone to
waterlogging. Some variations exist for
adapting to the erratic monsoon problems
and low-yielding direct-seeded rice by
transplanting rice by hand on to beds using
inverted-T openers to open the slots for
transplanting. There might be good prospects
for bed-planting of rice–vegetable
rotations in India or cotton–wheat rotations
in Pakistan.
Work is still needed to successfully
grow dry-seeded rice on beds, including
selecting sowing dates, weed management,
soil types and climatic and socio-economic
situations under which permanent beds
will be of benefit. There are still questions
to be answered about the shift from anaerobic
to aerobic fluctuating conditions for
rice. And there are questions about the most
appropriate machinery to be used, since the
more complex monsoon systems of Asia
might require more adaptation of designs
first created in the Yaqui Valley (Mexico)
ecosystem (Sayre and Hobbs, 2004).
The majority of current commercial
bed-planter designs are derivatives of
zero-tillage drills, using the same frames
and fluted roller seed meters, but with
simple adjustable-width furrower shovels
added. Much work has been undertaken on
the agronomy of wheat and rice and two
rows sown on 72.5 cm beds has become the
standard in rice–wheat rotations, although
most planters can be adjusted to three rows
and varying bed spacings. Some designs
offer zero-tillage bed-planter combination
machines that have extra inverted-T openers,
shovels and shapers. But these designs
seem to be inadequate for permanent beds
and increased residue levels, and work has
started on adding double disc openers and
star-wheel punch planters.
‘HAPPY SEEDER’. The ‘happy seeder’ (Fig.
14.17) was designed to handle high rates of
residue and seed either on beds or on the flat.
The drill is a combination of two machines,
a forage harvester and a zero-tillage drill
using inverted-T winged openers (RWC
website). The forage harvester cuts, chops
and lifts the straw, providing the drill with
a clean surface for zero-tillage drilling. The
chopped material is blown directly behind
the drill and floats down as mulch. Field
trials in India have confirmed the usefulness
of the approach. But problems with
germination and skips have persisted and
resulted in the need for adjustment for the
cutting height as well as strip tilling in front
of each inverted-T opener. Adaptations in
Pakistan have resulted in optional separation
of the two halves of the machine.
Small-scale Machine Design 219
Fig. 14.16. A multi-row rolling punch planter.
Two-wheeled tractors
Relative poverty results in landholdings
becoming smaller and more fragmented. A
successful small farmer might own 5 hectares
while a financially poor small farmer
will own less than a hectare with an average
of five fragmented parcels. The number of
four-wheeled tractors declines to virtually
zero for poor farmers, as does other modern
machinery. The eastern India and Bangladesh
areas (Fig. 14.18) have arguably the most
fertile land in all of South Asia; yet poverty
and very high population density offer conservation
agriculture researchers a particular
difficult and restrictive socio-economic
situation.
220 F. Ribeiro et al.
Fig. 14.17. An example of a ‘happy seeder’.
Fig. 14.18. The South Asian ‘poverty square’, where 500 million farm-supported families each live on
less than 1 hectare of land per farm.
If conservation agriculture is to be
introduced and adopted by farmers of this
region, the equipment must be adapted to
either bullock or two-wheel tractor power
sources. These power sources must also be
made widely available, as there are currently
large areas where even the simplest
power sources are not available. Two-wheeled
tractors have been seen as appropriate
and socially equitable (Justice and Biggs,
2004a), since the cost of keeping a pair of
bullocks for land preparation and some
transport are becoming prohibitively expensive.
Many farmers seek alternatives to
animal-drawn options, but developers here
and perhaps in other underdeveloped regions
face many extra hurdles:
1. The inherent conservative nature of all
farmers, but particularly those who are
resource-poor and can ill afford to take
cropping risks.
2. A substandard infrastructure, including
local manufacturers and extension systems,
together with low literacy, slows
interest in or adoption of any technology.
3. All farmers focus on low-cost machinery
investment and forgo quality for price.
4. The limited research and development
on conservation agriculture attachments for
two-wheeled tractors compared with fourwheeled
models.
5. Emphasis on four-wheeled tractors and
indigenous production has limited the
availability and competitiveness of twowheeled
models.
THE ROLE OF TRANSITIONAL TECHNOLOGIES.
Despite these hurdles, sales of two-wheeled
tractors and the common ‘rotovator’ have
increased in the last decade, especially in
Bangladesh, where it is estimated that more
than 400,000 Chinese-made two-wheeled
tractors undertake more than 70% of land
preparation by Bangladeshi farmers. This
dramatic increase was brought about by
changes in government policy and development
of a vibrant market for tractors following
a severe cyclone disaster and floods
in 1987 that decimated the animal population.
A similar picture is emerging in
Nepal and to some extent in India. Special
projects in Nepal have made farmers more
aware of the benefits of owning such power
sources to generate income or to provide
contractor services for non-owners of tractors
(Justice and Biggs, 2004b). The availability
of such power sources now allows
conservation agriculture methods and
techniques to be made available to farmers
in these regions.
Besides providing power for conservation
agriculture, these tractors undertake a
multitude of other activities, such as reaping,
pumping, seeding and tillage. The tractor,
or its engine, is also used as a power
source for threshers, winnowing fans, milling
and transport for people and goods,
both on land (pulling 2 t trailers) and on
water (thousands of country boats in Bangladesh).
They also reduce the drudgery of
puddling rice paddies when cage wheels
are fitted. All these functions speed up
farm operations (timely land preparation,
sowing and harvesting), improve yields and
increase cropping intensity and efficiency
of crop production. These results are all
vital for an area where population densities
exceed 1000 people per square arable
kilometre.
Land preparation costs for both winter
crops and summer puddling of rice are onethird
less per unit of land with two-wheeled
tractors than with four-wheeled tractors (Sah
et al., 2004). The time spent by four-wheeled
tractors in turning and backing is also eliminated
with two-wheeled tractors, especially
in small fields. The challenge has been to
extend these advantages to conservation
agriculture. First, a toolbar concept has been
used in zero-till and bed planters; and, secondly,
a reduced-till/shallow-till seed drill
has been modified to strip-till and form beds
in one operation.
TOOLBARS. As with four-wheeled tractors,
toolbar designs for two-wheeled tractors are
largely based on modifications of the familiar
‘rabi’ flat-bar seed drills. The mounting
plate for the toolbar is bolted to the rear of
the transmission of two-wheeled tractors.
Such a rigid mounting system in uneven
fields is a problem compared with more
flexible three-point-hitch systems. None the
Small-scale Machine Design 221
less, it has proved to be a robust platform
for conservation agriculture implements.
Generally, two bars are used to attach tools
and implements.
TOOLBAR ZERO-TILLAGE DRILLS. Most twowheeled
tractors are capable of pulling up to
four-row zero-tillage seeders. Designers have
simply adapted the designs of the fourwheeled
tractor zero-tillage drills to the
reduced row numbers, using full-sized
inverted-T openers and the same shanks but
having downsized the seed and fertilizer hoppers
(Fig. 14.19). The effective field capacity
of such machines is typically 0.20 ha/h for
simultaneous seeding and fertilizer application.
Planting cost for wheat and maize has
been reduced by some 50% compared with
conventional tillage methods.
TOOLBAR BED PLANTERS. Bed planters that
simultaneously till the soil and form the
bed are not considered, regardless of
whether or not they also sow seed and fertilizer,
although such a practice may eventually
lead to a full no-tillage programme
involving permanent beds.
Bed width is limited mainly by limitations
on wheel spacing of two-wheeled tractors.
The standard rice–wheat bed is 65–70 cm
wide. Problems occur when first forming
beds if the land is not previously prepared.
The shovels grab at clods, pulling the
machine off course, which may cause handling
problems if one wheel travels into a
furrow and tilts the bed former. Clods are
less of a problem under permanent bed conditions
where light reshaping of the bed is
performed and the wheels track nicely in
the furrows and greatly reduce fatigue of the
operator.
REDUCED-TILLAGE SEED DRILL. A Chinesedesigned
reduced-tillage/single-pass seed
drill was introduced into Nepal in 1989 and
Bangladesh in 1996 by CIMMYT. It has
been the only conservation technology
available from China for two-wheeled tractors
in those regions and has undergone
much research by Pradhan et al. (1997),
Meisner et al. (2003) and Sah et al. (2004),
who demonstrated consistently high yields
for the following reasons:
1. It was able to drill wheat, lentils and
other winter crops into very wet soils (up to
30% moisture content) immediately following
the rice harvest, avoiding late planting.
2. It provided a very fine soil tilth, which
ensures germination.
3. It placed seeds at a uniform depth.
4. It reduced weed problems associated
with the previous rice crop.
Although the machine cannot be considered
a true no-tillage drill when in its
full-tillage mode (Fig. 14.20), it represents
an excellent transitional (and flexible) technology
from multiple ploughing to zero- or
strip-tillage (Fig. 14.21). The drill’s three
main components are:
1. A 48-blade, 120 cm wide high-speed
shallow tillage (maximum 10 cm deep)
‘rotovator’.
2. A six-row fluted roller seed meter (11
and 17 flutes available) and seed bin.
3. A 120 cm roller for planking, compaction
and depth control.
STRIP TILLAGE. Research on strip tillage is
more recent (Justice et al., 2004), but results
have been promising using the Chinesedesigned
machine. Field efficiency improves
by 15–20% with less fuel and time consumption.
The soil area disturbed can be
adjusted from 15 cm to as little as 2–3 cm
(with straightened blades). For narrow
222 F. Ribeiro et al.
Fig. 14.19. A zero-tillage flat-type toolbar showing
the mounting plate for a two-wheeled tractor.
stripping, additional blade holders are
welded to the axle to compensate for the
absence of a normal spiral pattern and
to reduce vibrations. Work in Mexico,
Bangladesh and Nepal has shown that this
system’s high-speed ‘rotovator’ blades (which
rotate at greater than 400 rpm) are able to
cut and seed into loose straw and may
Small-scale Machine Design 223
Fig. 14.20. A two-wheeled reduced-tillage machine in full-width tillage mode.
Fig. 14.21. A two-wheeled reduced-tillage machine in strip-tillage mode.
present an inexpensive machinery solution
for the residue retention problems throughout
this region for two- and four-wheeled
tractors. Figure 14.21 shows a self-propelled
two-wheeled strip tillage machine creating
50% disturbance and sowing wheat in
100 mm spaced rows.
PERMANENT CONSERVATION AGRICULTURE BEDS.
The flexibility of the Chinese-designed drill
has recently been extended to making new
beds and seeding in permanent beds with
very few modifications. When it is necessary
to reshape permanent beds, the toolbar
system with shovels can be used, or only a
few rotary blades in the furrow might move
soil back on to the undisturbed bed.
STRIP TILLAGE ON PERMANENT BEDS. If the beds
do not require reshaping, the same machine
simply strip-tills on the existing beds. In
Mexico and Bangladesh, modifications to
conventional strip tillage machines have
been carried out by CIMMYT as follows:
1. Two depth-control wheels are positioned
in the furrows in place of the roller.
2. The furrow openers are extended down
about 7 cm.
3. The standard ‘C’-type blades are
straightened to cut through residue and
reduce the amount of soil movement.
4. Extra blades are added to reduce vibration
(circled in Fig. 14.22).
Figure 14.22 shows a modified strip tillage
machine/seed drill, in this case used for
drilling mung bean after wheat on permanent
beds. The straightened ‘C’-type blades
(inset) are able to cut the residue, leaving it
on the surface of the bed with minimal soil
disturbance or raking, which is otherwise
found with fixed inverted-T openers.
There has been much debate about the
most desirable height for beds of this type.
Most bed planters can only make beds up to
10–12 cm high. Early attempts to create
higher beds are now recognized as wasting
energy and are often agronomically undesirable
as they dry out more quickly. It is
now generally accepted that beds need only
to be as high as is necessary to allow water
to move from one end of the field to the
other for irrigation or to drain the field.
Because many fields are small (average less
than 0.2 ha), lower beds are sufficient.
Strip tillage systems based on twowheeled
tractors also involve comparatively
lightweight machines that allow
seeding into wetter soils compared with
four-wheeled tractors and their associated
bed planters. This is important in conservation
agriculture systems in South Asia with
both flat and low-bedded applications.
On the negative side, two-wheeled
strip tillage on permanent beds does not
allow access back into the field after the
crops are established. It would be desirable
to facilitate banded top dressing, inter-row
cultivation and spraying as with fourwheeled
tractor models.
Results of recent tests with wheat
establishment in Bangladesh (Rawson,
2004) found full tillage and strip tillage to
be initially superior to bed planting and
224 F. Ribeiro et al.
Fig. 14.22. A strip tillage drill operating in heavy residues on a permanent bed, sowing mungbean.
zero-tillage, but also noted that results
improved after operators had learned to
plant at the correct soil moisture content,
especially with no-tillage. As a result, it
is now believed that bed-planting and
no-tillage with two-wheeled tractors may be
the future of conservation agriculture in
that region.
Summary of No-tillage Drill and
Planter Design – Small-scale
Machines
1. Most small-scale farmers use either
hand-operated jabbing devices or drills and
planters with one or two rows pulled by
animal or small tractor power.
2. Small-scale no-tillage farming benefits
from increased operator attention to seeding
and weeding details.
3. Many designs of hand or animal planters
have evolved from simple ancient designs.
4. Small-scale opener designs have many
of the same requirements and designs used
on larger-scale farming presented in previous
chapters.
5. Some small-scale opener designs are
restricted by power, downforce and symmetry
requirements.
6. Providing separate fertilizer and seed
placement at seeding time is important to
enhance early crop availability and reduced
weed growth.
7. Seed and fertilizer metering devices
most commonly resemble adaptations of
those used in larger machines.
8. Hoe openers are more common in smallscale
farming due to increased penetration
capability compared with disc openers.
9. Residue handling is often easier with
small-scale machines as a result of fewer
rows and openers.
10. No-tillage in Asia presents special
problems associated with rice–wheat rotations
and monsoonal rains.
11. Extreme poverty is a further problem in
areas of Asia, which limits the sophistication
of no-tillage equipment and consulting
services to service farmers.
12. Widespread use of simple winged
(inverted-T) openers has opened opportunities
for no-tillage in Asia.
13. Bed planting and/or strip tillage is seen
as an interim step towards full no-tillage in
Asia.
14. ‘Happy seeders’, which combine forage
harvesters and seeders, allow residues to
be placed over the seed during no-tillage,
simulating some of the advantages of
larger-scale no-tillage machines.
Small-scale Machine Design 225
15 Managing a No-tillage Seeding
System
W. (Bill) R. Ritchie and C. John Baker
The overall success of a no-tillage seeding
system will be no greater than the least
successful component of that system.
Most of this book relates to the physical,
biological, chemical and economic risks
associated with equipment. But even the
best equipment available will not provide
optimum results if other input factors are
not of equal or similar standard. Consequently,
we must seriously consider the
other factors required to put together a successful
no-tillage seeding system that will
fully minimize the risks. We obviously cannot
provide a ‘recipe’ for fail-safe no-tillage
seeding in every condition. Each successful
package must be tailored to suit an individual
farm, field or field component.
This chapter briefly highlights the range
of factors that can influence the outcome
from no-tillage crop or pasture seeding when
undertaking a no-tillage system. A more
detailed outline of the way such factors interact
and how they determine the success or
otherwise of a no-tillage system as a whole is
given in Successful No-tillage in Crop and
Pasture Establishment (Ritchie et al., 2000).
Site Selection and Preparation
There is often little choice as to which field
or fields will be no-tilled. In other cases,
however, farmers may be in a position to be
more selective about fields, especially if
they are just beginning to convert from
tillage to no-tillage. If this is the case, it is
important to review the criteria that should
be considered.
Many who convert to no-tillage farming
do so on areas with a history of intensive
tillage that has resulted in poor soil structure,
low SOM, low soil microbial activity,
low earthworm numbers and possibly high
soil compaction. Such conditions are not
conducive to high yields from crops under
any crop-establishment system. Although
no-tillage would be expected to repair the
damage over time, the technique may be
disadvantaged in the short term. No-tillage
may not be an overnight cure for such conditions,
even though it is certainly a
long-term cure.
If correctly managed, no-tillage can
provide a sustainable method of crop production
while at the same time allowing the
natural processes of soil formation to continue.
These processes take time, perhaps
years and decades. Until a certain degree of
repair has occurred, yields may even be
reduced, especially if the farmer does not
apply the best-known inputs into the system.
But in other cases, where farmers have
used high levels of inputs, including
banded fertilizer, there are numerous field
examples where crop yields have not
© FAO and CAB International 2007. No-tillage Seeding and Conservation
226 Agriculture, 2nd edn. (eds C.J. Baker and K.E. Saxton)
suffered, even in the first year; and most
have steadily improved thereafter, often to
new levels never before experienced in that
field.
Best results for converting to no-tillage
will come where a farmer has the option to
select fields that have high potential returns
from the outset. On an integrated pasture
(sod) and crop farm, it may be most appropriate
to begin a no-tillage crop rotation in a
field that has been in pasture or lucerne for
some time and contains soil in better condition
than fields that have been cropped for
many years.
On farms that have been entirely tilled
in the past, fields that have been least
affected by the destructive aspects of tillage
should be chosen. It is unrealistic to expect
to objectively assess the potential of a system
such as no-tillage unless it has been
given a realistic opportunity to show its
true potential.
Effective soil drainage will have a
major influence on soil condition. While
no-tillage will improve the natural drainage
capabilities of a soil over time, some artificial
drainage may also be required. Welldrained
soils or fields will provide the best
results.
The importance of no-tillage openers
being able to faithfully follow ground
surface undulations has been outlined in
Chapter 8. But, whatever the merits of any
given technology in this respect, it will
perform more effectively and will allow
higher operating speeds to be used if the
field is smooth. When tilling a field prior
to converting to no-tillage, extra effort
should be put into smoothing the final surface,
a good investment for later no-tillage
farming.
It is worth noting, however, that, over
time, earthworm casting is capable of completely
levelling ruts as deep as 75–150 mm
(3–6 inches). But, of course, increases in
earthworm numbers are a medium-term
result of no-tillage rather than a short-term
effect.
Seeding with no-tillage drills or planters
will also be enhanced if fields are shaped so
as to provide relatively straight lands. The
firmer nature of untilled soils limits the
ability of many no-tillage machines to turn
sharp corners. Pre-planning during subdivision
can assist in this respect.
Weed Competition
Considerable discussion has centred on
weed competition in relation to openers. It
is important to remember that most of the
operations during conventional tillage are
designed to control competition with the
crop arising from weeds (unwanted plant
species). Consequently, the importance of
the spraying operation(s) in no-tillage cannot
be overstressed. Good management will
include careful identification of the weed
species, followed by careful selection of the
most appropriate herbicides or other weed
control strategy, such as mulching. Adequate
planning is important to ensure that
any residual herbicides used will be compatible
with the immediate and other future
crops, as well as desirable soil fauna such as
earthworms. Some herbicides and pesticides,
for example, are toxic to earthworms.
Having chosen the herbicide(s), additional
management input is required to
ensure that the specific chemical is applied
at the correct rate of the active ingredient,
with the correct rate of the carrier (usually
water) and any other allied chemical (e.g.
surfactant). Appropriate weather conditions
during and for a specified period after
spraying may be necessary. The particular
stage and vigour of growth of the plants or
size of leaf material may influence the
activity of the herbicide. With some herbicides,
there may be a minimum time period
between spraying and drilling. In most
cases, it is more critical to ensure that the
timing of herbicide application is optimized
with regard to that particular formulation
and the stage of growth of the weeds
unless there is residual activity from the
herbicide in the soil or danger of the ‘green
bridge’ effect (Chapter 3).
One principle that has repeatedly
occurred has been the shift in troublesome
weed species with continued years of notillage.
Each weed species has an optimum
pattern of tillage, crop competition and
Managing No-tillage Systems 227
moisture to establish. Almost all long-term
no-tillage studies with weed observations
have noted this distinct shift of both species
and intensity. But the same and other
longer-term studies show a significantly
reduced total weed incidence with continued
no-tillage systems that have used appropriate
control and crop rotation strategies.
Pest and Disease Control
Most of the same management principles
that apply to the control of weeds also
apply to the control of pests and diseases.
Accurate identification is essential to
ensure appropriate and cost-effective control.
Most importantly, it is necessary to
recognize that some pests and diseases
behave differently under no-tillage compared
with tillage. It can often be quite
misleading to assume that the control measures
appropriate to tilled soils can be
applied without modification to untilled
soils. These principles apply to both preand
post-drilling/planting management.
Chemical control measures may also be
complemented by other management techniques,
such as crop rotation, which is an
essential tool in the development of sustainability.
Not only is rotation effective to
control pests and diseases, but it can also
enhance weed control by allowing a wider
range of herbicides to be used and/or
enhancing the activity of particular herbicide
treatments, modifying soil fertility and
helping to raise SOM levels. Care must be
exercised, because the chemical eradication
of one unwanted pest species may be detrimental
to other wanted species, especially
earthworms.
Managing Soil Fertility
The development of no-tillage drilling
and planting technologies that provide separate
banding of fertilizer at the time of
drilling/planting has opened the door to new
opportunities for fertility management under
no-tillage. However, all of the old principles
apply.
The key to cost-effective fertilizer use is
accurate assessment of fertilizer levels and
crop requirements. Soil and plant tissue
analyses are useful tools in this process, as
is accurate interpretation of the results.
These results should then provide the basis
for the selection of the most cost-effective
fertilizer options, some of which might be
restricted by machine limitations while
others will not.
Considerably more site-specific research
may be needed under no-tillage to determine
the most appropriate fertilizer regime
for any given combination of crop, soil type
and climate under no-tillage. Fertilizer
responses under no-tillage can differ from
those under tillage in the same soil type. So
the extension of experiences and research
results under tillage may not necessarily be
appropriate when applied to no-tillage
systems. But plant requirements are generally
not changed. No-tillage seeding with
banded fertilizers offers an opportunity for
increased application efficiency, but the
total quantities of nutrients required, with
the exception of nitrogen, may not be
altered greatly.
Seeding Rates and Seed Quality
There is often considerable discussion
about optimum seeding rates for no-tillage.
Some have argued that seeding rates should
be increased, presumably to counter some
expected reduction in seed germination
and/or seedling emergence. This practice has
become known as using ‘insurance’ seeding
rates. But doing so, even with no-tillage
openers that have low emergence, can be
counterproductive if ideal conditions are
experienced that result in plant populations
exceeding the optimum. And high seeding
rates involve unnecessary extra seed cost.
There are few, if any, reasons for seedling
establishment from no-tillage to be any
lower than from conventional tillage if appropriate
equipment is used. In fact, with
advanced equipment and an appropriate
228 W.R. Ritchie and C.J. Baker
system, no-tillage has the potential for
higher establishment percentages than tillage.
In any case, it is not how much seed
that is sown that is important. Established
seedlings are the final measure. Therefore,
seeding rates should be based on an assessment
of the degree of risk associated with
any given situation, leading to a prediction
of the likely effective seedling emergence
(Ritchie et al., 1994, 2000). The first factor
to incorporate is the germination potential
of the seed, which is specified on the
seed certification data. Seeding rate can
then be calculated using the following
formula:
SR
TSW TPP
EFE
= ×
where: SR = seeding rate (kilograms per
hectare); TSW = thousand seed weight
(grams); TPP = target plant population
(plants per square metre); EFE = effective
field emergence (per cent).
The important principle is costeffectiveness
to produce the proper plant
density. To be confident of achieving a
target plant population, a farmer must use
seed of good quality in conjunction with
seeding equipment that provides reliable
seedling establishment under a wide range
of conditions.
Another important factor is accurate
calibration of both seed and fertilizer output
from the drill or planter. Because different
lines of the same seed species can vary
quite markedly in their seed weights and
sizes according to the vigour of the crop and
weather conditions and even the geographical
location at the time of harvest of the
particular line of seed, it is important to
calibrate the metering mechanism when
changing seed lines or varieties. A check on
calibration should be kept during drilling/
planting by matching seed and fertilizer
used to the area covered if monitors are not
available. Some seeders actually change
their metering rates with changing ambient
temperatures. The warming of the day from
morning to afternoon may bring about an
appreciable change in seeding rate with
such seeders.
Farmer experience in Western Australia
with the disc version of winged no-tillage
openers showed that seeding rates for an
equivalent canola stand could successfully
be reduced from 9 kg/ha under tillage to
4–5 kg/ha with no-tillage using an advanced
machine design (J. Stone, 1993, personal
communication). The resulting saving
in seed cost alone was equivalent to the
additional machine cost. Prior to reducing
the seeding rate, the experience of this operator
from sowing at the higher rate with
this no-tillage drill had been an overpopulated
crop, which remained largely vegetative
with poor crop yield.
Operator Skills
No-tillage is a relatively new technique to
tillage farmers. When undertaking conventional
tillage, farmers can draw on a long
history of tillage experience from most soil
types of the world, even if that experience
was not personal. However, only a limited
experience-base exists with no-tillage.
Further, that limited experience-base has
already shown that the two techniques are
quite distinct and that new skills must be
learned.
The ‘one-pass’ nature of no-tillage
leaves little latitude for error. On the other
hand, the range of implements and functions
involved is much smaller. Therefore, a
detailed knowledge of the key machines
(sprayers and seeders) can be more easily
gained.
Since soil physical conditions are more
likely to vary under no-tillage from field to
field, or even within a field, there is a much
greater need for the operator to understand
the principles involved under the conditions
and to be able to adjust the machine
accordingly. Of course, no-tillage drills and
planters vary widely in their respective
abilities to ignore soil variations by automatically
adjusting to them, but all will
require a reasonable level of operator skill
to achieve optimum performance.
It is likely that in the future we shall
see an increase in the use of electronic
Managing No-tillage Systems 229
monitoring and control of no-tillage drill
and planter functions to enhance performance
and reduce dependence on operator
skills. It is also likely that the operation of
no-tillage drills and planters will become a
more specialized task, with an increased
emphasis on operator training.
Post-seeding Management
A key catchphrase that has been coined for
the modern age of intensive agriculture is
‘knee-action farming’. The principle conveyed
by this term is the importance of
monitoring crop performance carefully and
regularly at close quarters throughout the
growth cycle. In many situations, this monitoring
involves kneeling down to inspect
the crop, rather than inspecting it from a
distance in a standing position, and often
with a magnifying glass in hand.
The ‘knee-action farming’ principle is
not exclusive to no-tillage systems but is
crucial to achieving consistently good cropping
results, and is especially important to
no-tillage because so many of the rules of
crop husbandry differ from those common
under tillage. No-tillage as a technique has
suffered in the past from a lack of analysis
of the reasons for poor results. Too often,
farmers and researchers have been prepared
to condemn no-tillage as a system on the
basis of a poor result without determining
the specific reason for the failure. This often
contrasts with an acceptance of failure in a
conventional tillage system on the basis of
poor weather, an ‘act of God’ or just plain
bad luck.
At times, there seems to have been a lack
of realization that tillage crop failures due to
severe wind or water erosion are not caused
by unfortunate timing but an inherent failure
of the tillage system to protect the crop from
such a risk in the first place. No-tillage
reduces some of those risks, but may introduce
other risks of a different nature. For
example, pest control becomes more important
in some no-tillage situations because
there is no physical destruction of their environment
by the tillage process. All of this
means that a farmer must maintain vigilance
over the crop to promptly react to crop management
problems that might arise. It is a necessary
advantage to have the skills to identify
specific problems and how to solve them or
know where to go for assistance. Regular,
close observation is an important tool for
‘knee-action’ farming.
Planning – the Ultimate
Management Tool
No-tillage is potentially a very flexible system.
It provides farmers with the opportunity
to respond at short notice to changes
in soil or climatic conditions or market
indicators. It is also a system, however,
that benefits from effective long-term planning
and regular reviews of the plan. The
success of a crop may well depend on the
implementation of a plan from several previous
months. For example, crop rotation
will influence weed management, pest and
disease management, fertility levels and
residue levels. Forward planning may well
provide key opportunities to take advantage
of these changing circumstances and
markets.
Residue management for no-tillage systems
is a case in point (see Chapter 10).
Obviously, decisions at harvest of the previous
crop will significantly influence the
next phase of the farming rotation, which
might occur several months hence. These
connecting events apply to chemical use,
equipment selection, fertilizer programmes,
crop rotation and harvesting patterns, all of
which emphasizes the role of forward planning
as a management tool.
Another example is the application of
lime to raise soil pH, which with no-tillage
should take place at least 6 months in
advance of drilling because without tillage
there is limited opportunity to mix this
low-solubility fertilizer with the soil.
Most other general aspects of managing
a crop production programme apply, such
as rigorous and regular maintenance of
drilling, planting and allied equipment and
230 W.R. Ritchie and C.J. Baker
maintaining regular contact with suppliers
and contractors to ensure that all components
of the programme come together
when required. Accurate record keeping
is an integral part of any effective management
programme.
Table 15.1 outlines the timing of many
of the key in-field management decisions
that need to be made in New Zealand if a
no-tillage programme is to succeed. It is not
intended as a recipe, but only to highlight
the important issues. Since many of the
Managing No-tillage Systems 231
When What to do Implications
Any time before
drilling
Ensure that drainage
is OK
No-tillage will not rectify poorly drained soils
Any time before
drilling
Determine how much
risk you are prepared
to take
Risk will be influenced by your choice of:
herbicide (effectiveness is a function of
conditions – poor conditions need better
formulations); slug bait (heavy infestations and
wet conditions need better formulations);
pesticide (ensure you have identified the target
pest and have chosen the correct treatment);
drill (difficult conditions and small seeds need
better technology); seed (difficult conditions will
place more pressure on seed quality)
Any time before
drilling
Check for pests that
are not specific to
no-tillage
Some pests may need treating before or at the
time of drilling. Consider using insecticidetreated
seed
Sometime before
drilling
Subsoil to alleviate
compaction if it exists.
Best done when soil
is dry
Use a subsoiler that does not disrupt the surface
sufficiently to require tillage to smooth it out
again. Slant-legged or shallow subsoilers are
best in this regard
When heavy stock is
removed from field
Smooth out hoof marks
greater than 75 mm
deep
Most drills will smooth out 75 mm deep hoof
marks as they drill (some do it better than
others). With deeper hoof marks use a ‘Ground
Hog’, shallow subsoiler or leveller to knock only
the surface humps off when the soil is
somewhat crumbly on top
6 months before
drilling
Apply lime if soil
pH is low
Lime takes longer to act when there is no
cultivation to incorporate it. Do not apply lime
close to spraying time. Lime on plant leaves
may affect the glyphosate and is slow to
dissolve and wash into the soil
3 months before
drilling
Take fertility
samples
It takes time to get the results, analyse fertilizer
options and take action. In long-term no-tillage
75 mm sampling may be more appropriate than
150 mm sampling
3 weeks before
drilling
Aim to spray with
glyphosate plus
chlorpyrifos if springtails,
aphid or Argentine stem
weevil are a risk
Where farmers do not want to use the higher
rates of chlorpyrifos, control of Argentine stem
weevil may be obtained by waiting 3 weeks
between spraying and drilling. However, you
need to be aware that a low rate of chlorpyrifos
may still be necessary to control springtails or
aphids
Continued
Table 15.1. An example of management steps for a no-tillage programme in New Zealand.
232 W.R. Ritchie and C.J. Baker
When What to do Implications
At least 2 weeks
before drilling
Remove stock from the
field (if it is in pasture
that has not already
been sprayed)
To be most effective, glyphosate should be
sprayed on to as much clean, freshly growing
leaf as possible. This also produces a heavy
mulch, which will help control weeds and retain
moisture, so long as the drill can handle the
heavy mulch. If necessary, pastures can be
grazed after spraying, provided that chlorpyrifos
has not been used.
Do not graze just before spraying, as leaf area
will be reduced. Besides, fresh animal manure
will reduce weed control and adversely affect
some drill openers. The time needed to ‘freshen
up’ a pasture will vary with growing conditions at
the time
10 days before
drilling
Check for the presence
of slugs
Scatter short lengths of smooth timber about each
field and leave for 2 or 3 days. One or two slugs on
the underside of a 300 mm length of 150 × 20 timber
indicates sufficient numbers to treat for
1 week before
drilling
Pre-bait for slugs This is only necessary for severe infestations.
Moderate or low infestations can be effectively
treated by applying baits at the time of drilling.
With heavy infestations, apply half the bait
1 week before drilling and the other half at (or
immediately after) drilling. Some drills can apply
slug bait as they drill, either surface broadcast or
‘down the spout’
1–10 days before
drilling
Spray glyphosate (to
control competition),
together with
chlorpyrifos (to control
pests)
Tank-mix chlorpyrifos with the glyphosate where
necessary to control pests. The longer the gap
between spraying and drilling, the more crumbly
the soil will become as roots decompose. But
also be aware that soil dries more slowly after
spraying because the plants are dead. In the
event of rain after spraying, the soil may stay wet
for longer.
When cutting pasture for silage, wait 3–4 days
after spraying before harvesting
1–3 days before
drilling
Look at the moisture
content of the soil
With most drills no-tillage works best when the
soil is a little on the dry side. Being patient and
waiting a few extra days often gives a better result
At the time of
drilling
Preferably apply all of
the crop’s fertilizer
requirements ‘down
the spout’. Crops like
winter wheat and maize
may also need further
fertilizer after
emergence
Only apply fertilizer ‘down the spout’ if the drill is
sophisticated enough to band it separately from
the seed (not mixed with the seed). Crop yield
responses to placed fertilizer under no-tillage
can be spectacular and there are generous limits
to what and how much can be applied. But only
a few advanced no-tillage drills do this. Where
such drills are not available, avoid putting any
fertilizer ‘down the spout’ at all, or be very careful
to select non-burn-type fertilizers. Broadcasting
is then the main option, although some people go
Table 15.1. Continued
Managing No-tillage Systems 233
to the trouble of drilling fertilizer alone first and
then drilling seed at a shallower depth as a
second operation
At the time of
drilling
Ensure all seed is sown
at the target depth
and covered
This is sometimes easier said than done unless
you have sophisticated no-tillage openers.
Where openers are not so sophisticated, a level
of risk must be accepted since germination and
emergence will then be highly dependent on
good weather, smooth fields and low residue
levels
At the time of
drilling
Apply slug bait This is most important with spring drilling but may
also be important in autumn. Moderate to light
infestations of slugs can usually be controlled by
applying slug bait either with the drill or as soon
as drilling has finished. Get specific information
from the experts on the effectiveness of different
baits
In the first 3 weeks
after drilling
Open slots and check
for slug damage
There is often a small window of opportunity to
apply slug baits after drilling if you have not
already done so and you find slugs feeding in the
slots
In the first 3 weeks
after drilling
Open slots and check
for twisted seedlings
Contrary to popular belief, twisted seedlings do not
indicate fertilizer burn. They indicate low-vigour
seeds. Do not be reluctant to have a sample of
seed tested for vigour (not to be confused with
germination) at a seed-testing laboratory. Almost
every case of twisted seedlings we have seen
has been caused by low-vigour seeds, which you
would need to talk to your seed merchant about
In the first 3 weeks
after drilling
Check for damage by
Argentine stem weevil,
springtails or aphids
All should have been controlled by tank-mixing the
appropriate amount of chlorpyrifos with the
glyphosate. But, if that did not occur, be extra
vigilant because these are the main pests of
no-tillage and can decimate an entire crop or
pasture
In the first 3 weeks
after drilling
Check for other pests
not controlled with
chlorpyrifos
Most normal pests of crop and pasture could also
be troublesome under no-tillage. Be at least as
vigilant as you would be with a tilled crop
4–6 weeks after
drilling pasture
Check new grass plants
for resistance to pulling
(by hand)
When new grass plants are not easily pulled from the
ground, they should be ready to be grazed lightly.
Use light stock in large mobs for a short period, rather
than set-stocking smaller mobs for long periods
After 6 weeks Treat crops or pastures
normally
That does not mean relax. It means that any
problems that do arise will be no worse than
under tillage. In fact, new no-tilled pastures,
because of the firmness of the soil, can often be
treated similarly to already established pastures.
Utilization of turnips and swedes will improve
because a greater proportion of the bulbs will be
above the ground
At harvest Spread crop residues
evenly
Do not burn crop residues except where the drill to
be used next will not handle them. Baling is
Continued
Table 15.1.
issues listed occur before the seed is sown,
forward planning becomes one of the most
important issues.
Cost Comparisons
No management analysis of a no-tillage system
would be complete without an examination
of the cost–benefits of choosing a
drill or planter with different complexity,
capability and cost. Economic studies
(Baker, 1993a, b, c, 1994, 1995) show that,
as the annual use of a seed drill increases, a
point is reached where there is little difference
in the ownership and operating costs
between simple low-cost machines and
large sophisticated (high technology) expensive
machines. Table 15.2 shows a comparison
of costs. While the absolute costs
and taxation rates shown in Table 15.2 will
not be generally applicable and will soon be
out of date, the relative values between the
various options are likely to be more nearly
universal.
At annual use levels of 50–100 hectares,
the large sophisticated drills are prohibitively
234 W.R. Ritchie and C.J. Baker
When What to do Implications
acceptable but will slow down the build-up of SOM.
With some drills, chopping of residues will be
necessary. Others can handle
any residue in any form. Still others cannot
handle any residues at all. Operators need to
know what drill will be used for the next no-tilled
crop before making decisions about what to do
with the residues from the present crop
After 1–5 years of
no-tillage
Examine your soil and
bank balance
Both will probably be improved. Soil structure,
health, porosity, organic matter and earthworm
activity will be noticeably improved. Provided
you have managed the system correctly and
used the appropriate levels of inputs for your
chosen level of risk acceptance, gross margins
should increase progressively
Table 15.1. Continued
Area drilled
(ha/year)
Simple
low-cost drills
Conventional
no-tillage drills
Sophisticated
heavy-duty drills
50 69 107 182
100 45 62 95
200 32 39 53
400 26 29 30
600 24 26 23
800 23 23 20
1000 23 21 18
Simple low-cost no-tillage drills = US$15,000.
Conventional no-tillage drills = US$30,000.
Sophisticated advanced no-tillage drills = US$65,000.
Other important assumptions: 24% marginal tax rate; inflation = 4%; interest rate = 11%; depreciation
allowance = 12.5%; analysis period = 5 years; tractor costs are additional.
Table 15.2. Comparative ownership and operating costs (US$/ha) of no-tillage drills.
expensive (US$95–182/ha) compared with
simple low-cost machines (US$45–69/ha).
However, from about 600 hectares per year
upwards, the differences are negligible, at
US$18–26/ha and may even favour the
larger machines. The data in Table 15.2 can
be considered conservative as they do not
account for increased seedling establishment
or yields likely to result from using
the more sophisticated machines. The costs
do, however, account for higher operating
speeds and lower maintenance for the more
advanced machines. Saxton and Baker
(1990), for example, found an advanced notillage
drill with winged openers increased
wheat yields an average of 13%. Calculations
using a higher marginal tax rate than
24% and/or lower interest rates than 11%
will result in the larger machines becoming
economic at a lower annual usage than 600
hectares per year.
Summary of Managing a No-tillage
Seeding System
1. The failure risk of a no-tillage seeding
system can be reduced by ensuring a high
level of input for all factors, not just the
seeding equipment.
2. Choose sites that will offer a high
potential return from the no-tillage system.
3. Chemicals generally replace tillage as a
means of weed control and must be selected
and applied with care.
4. Crop rotation can be an effective management
tool when used in conjunction
with chemicals to control weeds, pests and
diseases.
5. Some no-tillage seeding equipment
permits a wide range of options for fertilizer
application. Accurate analysis of soil fertility
levels and crop requirements will make
full use of this benefit.
6. Using excessive quantities of poorquality
seed to compensate for poor drill or
planter design or technique can be costly
and ineffective.
7. No-tillage requires that new operator
skills be learned but also offers the opportunity
for greater operator specialization.
8. An otherwise well managed and executed
no-tillage seeding programme can fail
from poor post-seeding crop observation and
follow-up.
9. Good planning of all aspects of the
no-tillage programme is a key part of risk
management.
10. Advanced no-tillage drills become
economic at about 600 hectares use per
year.
11. No-tillage is a short cut compared with
conventional tillage. Do not short cut the
short cut!
Managing No-tillage Systems 235
16 Controlled-traffic Farming as a
Complementary Practice to No-tillage
W.C. Tim Chamen
Removing vehicle-induced compaction from
the cropped area liberates crops and soils from
unnecessary stress, enhances their performance
and sustains production with the minimum
of inputs.
What is Controlled-traffic Farming?
Controlled-traffic farming (CTF) divides the
crop area and traffic lanes into distinctly and
permanently separated zones. All implements
have a particular span (or multiple of
it) and all wheel tracks are confined to specific
traffic lanes. It should not be confused
with tramline systems, which just provide
guidance for chemical applicators but do not
offer permanent separation of wheels and
crops. Figure 16.1 shows the system based on
existing technology. In the longer term, it is
likely that more specialized equipment will
be developed that will improve flexibility
and further enhance efficiency of the system.
Why Adopt a CTF Regime within a
No-tillage Farming System?
The benefits of CTF
Soils not only physically support crops;
they are also the medium through which
their roots grow and extract water, nutrients
and air to sustain their development. Confinement
or restriction of roots will almost
invariably lead to a negative outcome. Removing
vehicle-induced compaction improves
and sustains the health of soils. More rainfall
is absorbed and available to crop roots,
which in turn are better able to explore and
extract nutrients. Improved porosity also
ensures effective gaseous exchange and
drainage, both of which further improve the
potential for optimum crop performance.
No-tillage improves many critical soil
properties but some soils are still susceptible
to wheel and hoof compaction, no matter
how long they have been under no-tillage.
Machine performance is also improved
by the avoidance of mechanically induced
compaction. Variably compacted soils differ
greatly in their strength and response to
mechanical inputs. For example, this makes
it difficult to achieve optimum performance
of seed drill openers. Openers may work
well in one condition or position on a drill
and poorly or less well in others. A more
homogeneous soil condition over the field
provides greater machine precision. Soil
responses are more predictable and vary
less from point to point. Avoiding soil compaction
diminishes the heterogeneity (variability)
of soil properties both within and
between soil types, making them easier to
© FAO and CAB International 2007. No-tillage Seeding and Conservation
236 Agriculture, 2nd edn. (eds C.J. Baker and K.E. Saxton)
manage and more suitable for a wider range
of crops under a no-tillage regime.
The effects of CTF on soil conditions
No-tillage farming systems may cause varying
amounts of soil disturbance. Initially
no-tillage concentrated on avoiding general
tillage operations, but recent emphasis has
added the importance of minimizing the disturbance
created by the no-tillage tools (openers)
themselves. Low-disturbance no-tillage
is where drill and planter openers aim to disrupt
the soil as little as possible – sufficient
only to sow the seed and place the fertilizer,
but otherwise leaving the soil almost as if it
had not been drilled at all. Other forms of
no-tillage involve aggressive shank, hoe or
tined openers that leave the surface, and often
deeper layers, in a disturbed state resembling
the effects of minimum or reduced tillage.
Defining low-disturbance no-tillage is
difficult. A general rule of thumb is that at
least 70% of the original surface residues
should remain undisturbed after passage
of the drill. But, for openers operating at
750 mm row spacing, 30% disturbance
allows 112 mm either side of each row to be
disturbed, whereas, at 150 mm spacing, only
22.5 mmeither side of the row is acceptable.
In general terms, the greater the compaction
applied to the soil, the greater will be the
need for repair. No-tillage provides a large
measure of remedial action by reducing the
traffic intensity, avoiding soil disturbance
and allowing the soil to restructure. However,
removing the traffic altogether will allow this
to happen in greater measure and more
quickly. Central to the creation and maintenance
of an improved soil structure is the
minimization of disturbance, and, as we have
seen from the above, the more aggressive the
opener, the more disturbance there will be.
Unlike randomly trafficked soils, where
the openers may need to create a seedbed as
well as sow the seed, non-trafficked soils
tend to retain their seedbeds from one season
to the next, so that only seed and fertilizer
placement is required. From all points of
Controlled-traffic Farming 237
Fig. 16.1. A tractor-based controlled-traffic farming system showing drilling, spraying and harvesting.
On this scale, all wheel tracks other than those used for chemical applications might be sown.
view, the less the disturbance created during
seeding within a no-tillage regime, the better,
and CTF helps to make this possible. Where
comparisons have been made between random
trafficking and CTF, the research data
often do not include details about the opener
designs, and so the optimum no-tillage conditions
for the trials may not always have
been present, which may or may not have
affected the comparisons.
Soil strength
The strength of soils is governed by a number
of factors, some of which are interrelated and
all of which have an impact on no-tillage.
Compacted soils are stronger and have greater
resistance to penetration than non-compacted
soils, particularly when their water contents
diminish (Blackwell et al., 1985; Campbell
et al., 1986; Gerik et al., 1987; Chamen et al.,
1990, 1992; Dickson and Campbell, 1990;
Carter et al., 1991; Unger, 1996; Radford
et al., 2000; Yavuzcan, 2000; Abu-Hamdeh,
2003; Radford and Yule, 2003).
In a 10-year experiment, one particular
treatment subjected a moist (25–32% water
content) Vertisol to a wheel load of 5 t in
year 1 and 3 t annually thereafter for 5 years
(Radford and Yule, 2003). Tillage to control
weeds was used in the first 5 years of an arable
rotation. At the end of the initial 5 years,
no-tillage and controlled traffic were applied
for a further 5 years to these same plots.
The greater shear strength persisted in the
0–100 mm profile for over 3 years, while, in
a treatment with repeated 5 t wheel loads in
all of the first 5 years (compared with the 3 t
after year 1), strength effects to 100 mm persisted
for nearly 5 years after no-tillage was
introduced.
These data suggest that randomly trafficked
soils may exhibit high levels of variability
in strength as a result of a history of
indiscriminate wheeling. Although these
differences may tend to diminish with time
under a no-tillage regime, the natural amelioration
in the top and most important few
centimetres will tend to differ according to
soil type, opener design and newly applied
traffic. Added to this will be a general
increase in soil strength arising from repeated
wheel passes. On some soils this may not be
completely counteracted by structural improvements
resulting from lack of disturbance
or by a greater concentration of organic
matter in the surface layers.
EFFECTS OF SOIL STRENGTH ON NUTRIENTS AND
SEEDLING GROWTH. Increased soil strength
reduces a crop’s ability to extract nutrients
and as a result some will be lost from the
soil system. With any particular soil, strength
variation is dominated by changes in water
content, but strength at a specific water content
is determined by its state of compactness.
Denitrification caused by compaction
is a source of nitrogen loss, and restricted
rooting may cause poor phosphorus uptake
(Wolkowski, 1990, 1991). Potassium uptake
is primarily affected by aeration. Below an
oxygen concentration of about 10%, uptake
is impaired.
Denitrification may lead to fertilizer loss
with no-tillage in wet conditions (Torbert
and Reeves, 1995). When the soil is dry,
uptake of N can be compaction-impaired by
limiting root growth. This effect has been the
cause of N loss, particularly under no-tillage,
following N fertilization and heavy rainfall
(Ball et al., 1999). Denitrification and methane
production were identified as one of the
main constraints to the improved environmental
performance of no-tillage compared
with reduced tillage (King et al., 2004).
King et al. attributed this to an increase in
the bulk density of the topsoil and to poor
aeration.
Soil strength directly above emerging
seedlings may also be an issue. Addae et al.
(1991) suggested the following relationship:
Y = 90.4 – 3.58X
where:
Y = seedling emergence, percentage
X = soil strength, kPa
The maximum force that a wheat seedling
coleoptile can exert is around 30 g and only
when resistance is less than 25 g can 100%
emergence be expected (Bouaziz et al., 1990).
238 W.C.T. Chamen
Compaction of the soil above an emerging
seedling therefore reduces emergence,
particularly if the soil is wet. Variation in
the time to emergence is also often associated
with soil strength variations (Brown,
1997).
EFFECTS OF SOIL STRUCTURE ON SOIL STRENGTH.
Increased soil strength can be attributed to
changes in soil structure. It is a readily
observable fact that compacted non-shrinking
clay soils exhibit plasticity when moist and
cloddiness when dry. They rarely display
the friability and flow characteristics of
non-compacted granular material. Consequently,
randomly trafficked soils not only
reveal large variations in penetration resistance,
but they also react differently when
disturbed. In some areas they will flow and in
others they will smear or fracture into variably
sized and often large aggregates. This is not
easy to deal with when designing an opener
to work consistently within a given soil type at
a given moisture content. It is even more difficult
when soil type changes across a given
field. To overcome the problem of variable
penetration depth, electromechanical control
systems for no-tillage drills have recently
been designed to cope with changes in soil
strength and go a long way towards overcoming
the problem (see Chapter 13).
One of the outcomes of tillage to remedy
compaction, in an attempt to create a
uniform but artificially structured seedbed,
is interruption of natural soil structuralforming
processes. This is despite the fact
that the very mechanical processes being
employed will themselves immediately
render that soil more susceptible to the negative
effects of random wheeling and other
compacting influences. Therefore, although
tillage temporarily makes the operation of
seed drills relatively simple, it commits soil
to a downward negative spiral of compaction
and structural degradation and has never
been a long-term answer.
Cockcroft and Olsson (2000) suggested
that no-tillage and zero traffic could not
avoid the problem of hard setting on some
soils. Although biopores help the infiltration
of water and more organic matter improves
the situation, drainage and root growth can
still be impaired. A sustainable solution has
yet to be found for these soils.
EFFECTS OF SOIL STRENGTH ON DRAUGHT FORCES
AND IMPLEMENT WEAR. Although no-tillage
aims to minimize soil disturbance, the force
required to displace soil during sowing is
still directly proportional to its strength.
Chamen et al. (1990) reported a 25% reduction
in energy requirement for no-tillage in
non-trafficked compared with trafficked soil,
despite a slightly greater depth of operation
(56 mm in the non-trafficked compared with
50 mm in the trafficked soil). This is similar
to reported reductions in energy for tine tillage
in trafficked and non-trafficked soil
(Lamers et al., 1986).
A further consequence of lower soil
strength is proportional reductions in wear
on soil-engaging components. Lower wear
saves on replacements and also saves on
labour and downtime to fit new components.
While in tilled soils and some untilled
soils it is often found that openers working
behind wheels require replacement more
frequently than elsewhere, in other situations
the reverse may be true. When operating
no-tillage drills in long-term pasture with
good load-bearing ability in New Zealand,
often the surface disturbance resulting from
wheel slip by the tractor tyres loosens rather
than compacts the soil and wear of openers
in those wheel marks is reduced [Eds].
Soil structure
Avoiding vehicle-induced soil compaction
can have a major impact on the structurerelated
aspects of water and gas movement
in and out of the soil. Much research has concentrated
on these characteristics. McQueen
and Shepherd (2002) concluded that some
soils brought into cropping from permanent
pasture could suffer from soil deformation
caused by traffic. Compaction, even on
no-tillage soils, reduced water infiltration
(Ankeny et al., 1990; Meek et al., 1990; Li
et al., 2001), soil porosity, saturated hydraulic
conductivity (Wagger and Denton, 1989), airfilled
porosity and permeability (Blackwell
et al., 1985; Campbell et al., 1986).
Controlled-traffic Farming 239
On the other hand, minimal-disturbance
no-tillage openers operating in silty soils in
New Zealand have been shown to leave
most indices of soil health (including soil
structure) in a similar state to the original
permanent pasture. Even after 20 years of
continuous double cropping with no-tillage
and random and repeated trafficking, there
was no obvious effect on such soils compared
with their pasture equivalents (Anon., 2000;
Ross et al., 2000, 2002a, b; Ross, 2001,
2002) [Eds].
Both air capacity and available water
are primarily affected by bulk density,
organic carbon and clay content, the latter
being relatively more important in subsoils.
Variability in air capacity and available water
is highly dependent on bulk density and
soil texture. In a clay loam, available water
has been halved with an increase in bulk
density from 1.4 g/cm3 to 1.75 g/cm3 (Hall
et al., 1977).
Reduced infiltration due to traffic compaction
can increase runoff and erosion.
Wang et al. (2003) measured a twofold
increase in runoff on trafficked compared
with non-trafficked no-tillage plots and an
approximate threefold increase in soil loss.
Environmental improvements associated
with non-compacted soils also relate to
gaseous losses to the atmosphere. Reduced
air-filled porosity due to compaction leads
to denitrification in clay soils. Similarly,
no-tillage and controlled traffic appear to
preserve CH4 oxidation rates (Ball et al.,
1999).
There is also evidence of improved
water availability to crops on some nontrafficked,
albeit shallow-tilled (100 mm)
clay soils. Changes in matric potential at
150 mm depth over a 48 h period showed
large fluctuations on a trafficked soil compared
with relatively small changes on
non-trafficked soil. The latter reinforces the
importance of promoting natural soil structure
through both no-tillage and controlled
traffic (Chamen and Longstaff, 1995).
Campbell et al. (1986) working on a
sandy clay loam found that, in the absence
of traffic, the soil could be reclassified from
being unsuitable to being entirely suitable
for no-tillage.
The implications of CTF for no-tillage
operations
RESIDUES AND RESIDUE HANDLING. Residues
are a critical issue in no-tillage systems
because they are not incorporated into the
soil before the next crop is drilled. Indeed,
many of the benefits of no-tillage accrue from
this fact. It is preferable to leave the residues
in situ on the soil surface to decay slowly
and for both the residues themselves and
their decayed products to be gradually incorporated
into the soil by fauna such as earthworms.
This is also advantageous in terms
of nitrogen, which is often temporarily
locked up by rapid organic matter decomposition.
Residue management prior to
and during drilling is therefore particularly
important if the crop is to be sown without
interference or subsequent adverse effects
on germination and seedling growth.
The additional precision afforded by
controlled traffic (see next section) should
allow crop residues to be manipulated and
placed more precisely, if required. For example,
the tendency to use wider equipment is
already initiating the design of more accurate
residue placement methods by harvesters.
Working from permanent wheel ways created
as part of carefully prescribed routes and
where future sowing lines are predetermined,
residues could specifically be placed to
avoid the new crop row.
With random traffic systems, crop stubbles
and residues are flattened in an arbitrary
way, resulting in their variable orientation
to drill openers. Some openers do not perform
reliably in these conditions; while others
not only perform reliably but they utilize
random residues to control the seed microenvironment.
Controlled traffic avoids random
stubble trampling and its associated
variability. It is possible, for example, to
develop the system where small grains have
been stripped from straw that remains standing
following the harvester pass. Both manual
and assisted-guidance methods could then
allow sowing between the standing straw
rows and into soil that may only have a covering
of the chaff and light fraction (Fig. 16.2).
There will be additional effects on residues
from increased earthworm activity in
240 W.C.T. Chamen
non-trafficked soils. Radford et al. (2001)
recorded an increase in earthworm numbers
from 2 to 41/m2 when all compaction on a
moist vertisol was avoided. Pangnakorn et al.
(2003) found a favourable differential of 26%
in numbers of earthworms in no-till compared
with cultivated soils and an additional
14% increase when traffic was removed.
Compaction restricts oxygen supply,
nutrient intake and physical movement.
Although the effect of additional earthworm
activity is unlikely to have a direct effect on
the sowing operation in terms of residues,
the reverse is often true. Residues encourage
earthworms and they in turn may improve
seedling emergence, particularly in wet soils,
primarily as a result of improved porosity.
(Chaudry and Baker, 1988; Giles 1994).
Considering that there are increasing
levels of CO2 in the atmosphere and this
scenario is likely to continue, crop and
weed residues and crop yields are likely
to increase (Prior et al., 2003). Improved
management of residues will therefore be of
increasing importance, not only to deal with
the quantity, but also to avoid a temporary
lock-up of nutrients and longer-term excessive
acidity in the surface layers. This issue
remains to be dealt with adequately.
WEED CONTROL. Traditional cultivation systems
use a combination of cultural, chemical
and tillage methods to achieve weed control.
Weeds are always a threat to the sustainability
of cropping, and they continuously
evolve to overcome any particular means of
control. The most recent example of this is
the resistance of Lolium rigidum (annual
ryegrass) to glyphosate (Wakelin et al., 2004).
Therefore, it can be argued that reducing the
number of options for weed management is
risky; but there are positive aspects too, some
of which are aided by CTF, the most important
of which is minimizing soil disturbance.
There are several approaches that
improve weed control without tillage. One
of the few defendable objectives of tillage is
to stimulate weed seed germination so that
the offending seedlings can be killed by a
subsequent tillage operation. In the absence
of such stimulation, the most widely practised
weed control measure is to blanket
spray with either selective or non-selective
herbicides. CTF will make this more efficient
because a greater proportion of weed
seeds are likely to germinate during the
inter-crop period. Seeds lying on a friable
soil surface are more likely to germinate
through intimate soil contact or by burial,
either through their own activities (e.g. wild
oats, Avena fatua) or external forces such as
rainfall, frost, wind or the activities of soil
fauna. After spraying, the aim is to avoid
further weed seed germination, and crucial
to the success of this is the minimization of
soil disturbance by the no-tillage openers.
This approach has been effective in
New Zealand. Troublesome weeds such as
wild turnip had forced many farmers to stop
growing forage brassicas by conventional
tillage because of the difficulty in controlling
volunteer wild turnip plants, the seeds
Controlled-traffic Farming 241
Fig. 16.2. Soil and residue conditions following
grain stripping. Global positioning systems (GPS)
and other precision guidance methods allow
sowing to take place between the rows in a CTF
regime.
of which may remain dormant in undisturbed
soil for up to 40 years. Even vigorous
no-tillage openers often disturbed sufficient
soil within the rows to create rows of the
weeds where none had existed before drilling.
But use of the disc version of winged
no-tillage openers or double disc openers,
either of which minimizes surface disturbance,
avoids the problem [Eds].
After drilling, it may be possible to utilize
the close precision of CTF to target
inter-row weeds that will either germinate
as a function of their own activity (as described
above) or be prompted to do so by
shallow inter-row tillage with a light implement.
Inter-row flaming, steaming, mowing
and non-selective herbicides can then be
applied where there is sufficient room
between the rows. Vision guidance methods
for doing this are now fast and reliable.
The efficiency of spray booms is likely
to be improved by CTF systems. Most CTF
systems use extended track widths and it is
anticipated that future developments will
provide additional boom support even further
from the boom centre. Improved stability
reduces roll and allows booms to be positioned
closer to the crop or ground without
fear of contact. The auto-guidance systems
generally associated with CTF also reduce
boom yaw, a feature associated with manual
overcorrection of steering. Reduction of
roll and yaw improve the application accuracy
while diminishing the risk of drift.
OPENER DESIGN AND PERFORMANCE. The main
implication of CTF for no-tillage opener
designs involves the general reduction in soil
strength in the absence of vehicle-induced
compaction. This reduces the penetration
and draught forces required between wheeled
and non-wheeled areas. Chamen et al.
(1990) found that a triple disc opener
pressed into non-trafficked no-tillage soil
by rubber buffers penetrated too deeply. A
solution was to use a traditional single disc
opener designed for cultivated soils. Thus it
may be seen that no-tillage seeding on nontrafficked
soils can be carried out with significantly
lighter and less robust machines.
Non-trafficked soils tend to present a
more friable seedbed regardless of the soil
moisture regime. This can have negative as
well as positive effects. The positive effects
are obvious and important, but hairpinning
with discs may be a greater problem with
CTF because there is less soil resistance to
the vertical cutting of residues. Setting the
discs deeper is unattractive because draught
forces and soil disturbance are greatly
increased. Other options include managing
the residues to avoid their presence in the
sowing line (Fig. 16.2) and using openers
that do not create hairpinning or deliberately
separate the seed from contact with hairpinned
residues. The disc version of a
winged opener places seeds to one side of
any hairpins that the central disc may create,
and eliminates this problem. The more friable
nature of the soil under CTF will have
largely a neutral effect on hairpinning with
this opener [Eds].
Wide spacing of narrow tines works
well in dry conditions but becomes unacceptable
in moist soils because of the large
wedges of residue left as the tines eventually
clear themselves (see Chapter 10). Punch
planters show promise if hairpinning can
be avoided, but their potential has been limited
by the high strength of trafficked soils.
The greatest problems will be with moist
clays, when fine soil and residues cling to
every part of the opener. Experience of these
conditions within a CTF regime is still limited
and further use and customized opener
development are needed.
On a more general note, the more friable
seedbed structure associated with CTF
should ensure that the firming devices of
seed openers operate more effectively. As
suggested by Baker and Mai (1982b) and
Addae et al. (1991), firming should be
around or under the seed, not above it. With
CTF, a more homogeneous soil condition is
likely to be presented to the opener and
there will therefore be less need for compromises
in depth settings between individual
openers and less variation in seed covering.
There will also be less wear, lower overall
draught and reduced power and traction
demands.
Figure 16.3 shows how two disc-type
openers on the same machine can perform
very differently, depending on whether
242 W.C.T. Chamen
they are behind wheels or in between.
In the absence of differential rutting from
wheels, the soil surface will also be smoother.
This reduces the potential for differences
in opener performance, particularly
where they are mounted in gangs. Openers
mounted individually on parallel linkages
will be less prone to depth variation where
ruts are present, but a more level surface
will still have a positive influence on their
performance.
Consistent sowing depth is vital to avoid
too shallow planting in dry conditions or too
deep in others, and Kirby (1993) noted that
the time to emergence was extended as sowing
depth increased. Heege (1993) found
that, in the range of cereal seeding depths
from 25 to 45 mm, field emergence dropped
from 82% when the depth varied by around
6 mm, to 50% when the variation increased
to 20 mm. Heege and Kirby both found
that rate of emergence affected subsequent
growth, as did Benjamin (1990). They all
suggested that differences in date of emergence
were perpetuated and even exacerbated
in subsequent growth. Although these
differences may not be large enough to create
differences in yield, they do make it more
difficult to estimate crop growth stage for
chemical applications. Additionally, this
means that a larger proportion of the crop
will be treated at the wrong growth stage
and, as a result, suffer a greater setback.
In summary, fewer differences in soil
strength and a more level surface will both
help to make sowing depth more consistent.
This minimizes crop emergence time and
makes subsequent management easier and
more effective.
The implications of CTF for soils and crops
AGRONOMY. Provided that severely compacted
soils are loosened before introducing
CTF, it seems certain that the problem
of poor initial crop growth and loss of nitrogen
through denitrification will be reduced,
particularly in the early years of no-tillage.
Improved initial growth will be promoted
by the lack of a compacted surface layer and
encourages crop root growth, which explores
and extracts nutrients from a greater proportion
of the profile.
Australian farmers have found that row
cropping is a natural extension to controlled
traffic. This is possible because the position
of each crop row can be planned in advance
and achieved in practice with precision
guidance techniques.
Seed rates have often been increased
slightly with no-tillage, although rates of
several crops have been actually reduced
with advanced no-tillage openers (Baker
et al., 2001). Regardless, controlled traffic
makes seeding more reliable and works in
favour of lowering seed rates because the
surface is more level and there is less compaction
variation across the drill width.
Without compaction, many soils form a stable
fine crumb at the surface, which readily
accepts seeds with minimal disturbance.
This makes drill setting easier, reduces
Controlled-traffic Farming 243
Fig. 16.3. Performance of two closely adjacent openers on the same drill working in a moist clay soil.
The opener was behind the tractor wheels in the left photo and the seed is clearly visible on the surface,
while on the right it was operating correctly in less compacted soil.
irregularities in performance and avoids
the need for increased ‘insurance’ seed
rates.
A no-tillage farmer in the UK
(Hollbrook, 1995) found that spring barley
sown 3–4 mm deep was noticeably healthier
than the crop sown at 40–50 mm. Shallow
sowing resulted in the first node emerging
from the coleoptile when it was 20–30 mm
above ground rather than at the surface.
This precluded the incidence of eyespot
(Cercosporella) and subsequent weakness of
straws, which often resulted in crop lodging.
Slugs (Deroceras reticulatum) have frequently
been a problem with cropping systems
that retain surface residues, and
particularly those with cloddy seedbeds and
smeared and open sowing slots (Moens,
1989). Slugs attack crops in two ways – below
ground, where they eat the seeds, and above
ground, where they eat the young leaves.
Openers that produce small clods mean that
slugs can access seeds more readily, while
open or smeared sowing lines allow them to
move unhindered from one seed to the next.
CTF has the potential to address these problems
through the avoidance of ‘cloddiness’
and smeared sowing lines.
CROP YIELDS. Most research comparing
trafficked and non-trafficked soils has been
with systems using cultivation, but work on
no-till in Scotland found that, even with
fairly modest wheel loads, no-tillage yields
were reduced. This occurred in the early
years of no-tillage, but differences were
absent by the fourth season, despite no
actual reduction in bulk density on the trafficked
soil (Campbell et al., 1986). In the
USA and in Argentina, soybean yields in
no-tillage systems were reduced by between
10% and 39% with repeated but often quite
modest wheel loads. Even where no-tillage
had been practised for 7 years it was still
possible to reduce yields as a result of
newly imposed wheel loads (Flowers and
Lal, 1998; Botta et al., 2004).
RANGE OF CROPS. Although we have concentrated
primarily on small-grain cropping,
the introduction of CTF should make
it possible to grow a wider range of crops
with no-tillage. No-tillage establishment of
cotton, for example, was successful even in
the presence of wheel compaction. Lint yields
for no-tillage were only reduced in one year
out of three, while those for transplanted
tomatoes, albeit with strip tillage, were
comparable at two sites in 2002. Strip tillage
for melons resulted in marginally lower
yields than the traditional method, but, with
both tomatoes and melons, ‘cloddy’ soil conditions
at planting/sowing were partly responsible
for the poorer crop performance. A
vegetable producer in Australia growing
tomatoes, zucchini, melons, onions and
broccoli predicted that CTF would allow
him to establish these crops with no-tillage.
Potatoes have also been grown successfully
with deep mulches and no-tillage (Lamarca,
1998; Mitchell et al., 2004a, b; Ziebarth,
2003, personal communication).
The possible constraints on cropping
within a no-tillage CTF regime arise from a
number of sources:
● Soil structure/crop interactions.
● Inexperience and perception.
● Machinery.
Because completely non-trafficked soil has
until recently been largely unknown within
farming systems, it is difficult to predict
how some crops will react to these notillage
conditions. Equally, there are very
few data that might be used to determine
whether crops such as carrots, sugar beet
and potatoes will perform adequately in
non-trafficked, non-tilled soil.
The only way that this might be determined
is through the comparison of a number
of soil parameters, such as bulk density,
penetration resistance and porosity. For
example, does the bulk density of a given
non-trafficked non-tilled soil exceed that of
its cultivated counterpart for a particular
crop? In addition, within what soil environment
will a root crop perform equally to
that of the cultivated norm? Many of these
questions remain unanswered. We shall
also have to be aware that considerable soil
disturbance is often experienced during
the harvest of root crops. Although this
would at least partly interrupt the no-tillage
cycle, it would still be advantageous for the
244 W.C.T. Chamen
remainder of the rotation and for establishment
of the root crop. Controlled traffic
would also minimize the repair needed after
harvesting and ensure a quick and effective
return to no-tillage.
The crops that we can probably grow
now under a CTF regime with a proven agronomy
based on no-tillage include:
This range is necessarily more limited than
mentioned previously, and further technological
developments and in-field experience
are needed before more crops can be
considered. However, given the characteristics
of these crops and the typical climatic
conditions under which they have been
successful, it would be quite rational to
extrapolate to other crops and climates in
locations where CTF no-tillage farming has
not been extensively attempted.
Making CTF Happen
Basic principles
There are several principles involved in
CTF:
1. Forward planning.
2. Matching of vehicle track widths.
3. Matching of single (primary) or multiples
of implement widths.
4. Discipline.
These principles will be outlined in the following
sections, but far greater detail can be
found in Tramline Farming Systems, published
by the Department of Agriculture,
Western Australia (Webb et al., 2000), in
conjunction with the Grains Research and
Development Corporation.
Forward planning and machinery
matching
Planning is probably the most important
aspect of conversion to CTF, because it
ensures, amongst other things, that the cost
is kept to a minimum. Some farms may be
able to convert within 12 months; others
may require planning and change extending
over several years. In the context of this
book, it is assumed that the end point of
transition is a no-tillage crop establishment
system, but the starting point could be
mouldboard ploughing, secondary cultivation
and drilling. There must therefore be
an initial commitment to a significantly
lower input system. In some ways, changing
from an extensive machinery system makes
the economics easier because the excess
machinery can be sold and appropriately
sized new or second-hand equipment purchased,
probably at little additional cost. It
will also entail a reduction in labour. The
economics, however, will be dominated by
the change to no-tillage rather than to CTF.
If a minimum- or no-tillage system is already
being used, the transition may have to be
planned more carefully and over a longer
timescale because fewer costs will be lost
from the system, but returns will still be
improved.
The width-matching process
The objective is to match all implement
working widths, on the one hand, and
machine track widths, on the other. The
purpose is to minimize costs and number of
wheel tracks per unit area. The cost factor
means that most transitions will start with
examination of existing equipment to consider
its adaptability. As an example, take
a small farm growing grain crops with a
minimum-tillage system that has a 3.5 m
wide cultivator, a 5 m wide roll and a 3 m
drill; the cereal harvester is 6.1 m wide and
chemicals are applied with 12 m booms.
Tractors are on track widths varying from
1.5 to 1.8 m and trailers have a track of
around 1.8 m; the harvester is on 2.8 m. In
effect, nothing matches up with anything in
Controlled-traffic Farming 245
● Wheat ● Barley
● Oats ● Rye
● Sorghum ● Millet
● Oilseed rape ● Maize
● Soybean ● Dry peas
● Field beans ● Linseed
● Dryland rice ● Cotton
terms of controlled traffic (Fig. 16.4, left).
The tractor wheel track settings can, however,
be changed to 1.8 m (to match the
trailers) relatively easily.
Two challenges remain – the track
width of the harvester and the choice and
width of no-tillage drill. If the 6.1 m harvester
is to be retained, the drill should be
6 m wide (to ensure that the harvester gathers
the entire crop on most occasions) and
the cost of this will need to be budgeted,
with allowance made for the second-hand
value of the existing drill, cultivator and the
rolls (the economics of CTF will be studied
more closely in a later section). It may also
be possible to sell one tractor, but one of the
remaining tractors must be capable of pulling
the proposed replacement drill or a new
(larger) tractor will have to be purchased.
The harvester track width cannot easily
be changed and these wheels will be the
one set that extend outside the primary
track width. Their position, however, is
known and they will not necessarily cause
damage every season because soils are often
drier at this time (and therefore able to
withstand more weight) than at sowing. If
compaction and surface rutting occur, they
can be repaired with a subsoiler having tines
positioned so that they loosen just the additional
width imposed by the harvester. A
6 m system as described will create wheel
ways that cover around 16% of the area,
depending on the width of the tyres used.
Providing the wheel ways are well maintained,
it may be possible in the longer term
to fit narrower tyres.
On a larger farm, an alternative might
be to use a ‘twin-track’ CTF system. This
largely eliminates the harvester problem,
while maintaining wheel track settings more
or less as standard. Figure 16.5 shows that
the system works by straddling the harvester
across adjacent passes of the primary
246 W.C.T. Chamen
Fig. 16.4. Placing all the
equipment in the example around
a common centre line (left) shows
that it is only the harvester that
has a significantly different track
width. Available settings on the
tractors will allow them to be
aligned with the trailers, as
indicated on the right, with only
the cost of time.
Fig. 16.5. Twin-track CTF system,
where the harvester straddles single
tracks of adjacent pairs of tractor tracks.
Primary implement width is determined
by the addition of the tractor and
harvester track widths.
tracks. The primary implement width is
determined from the simple addition of the
common track width of the tractors, trailers
and chemical application equipment, plus
the harvester track width. In the example
above, primary implement width would be:
1.8 + 2.8 = 4.6 m. The harvester cutting
width can be any multiple of this; in this
instance, the most practical would be 4.6 or
9.2 m. The drilling width, however, can
only be odd multiples of the primary implement
width and this probably limits it to a
single multiple. Chemical applications can
be any multiple of the primary implement
width if the primary tracks are used, e.g.
4.6 m, 9.2 m, etc. If the chemical application
equipment is on a wide axle and runs on
the harvester tracks (to improve the stability
of the applicator), the width of the chemical
application equipment can only be
even multiples of the primary implement
width.
Presently none of the implement widths
quoted above is standard, so some adjustment
to the primary track width might be
needed even in a twin-track system. For
example, if the primary track were narrowed
to 1.7 m, this would correspond with available
harvester widths (9 m) and chemical
application equipment (18 m, 27 m, 36 m).
Alternatively, the track settings could be
2 m and 3 m, giving a primary implement
width of 5 m. The harvester cutting width
should be slightly wider than the calculated
width to ensure capture of the entire crop in
all circumstances.
A further method of matching is to
align all field machinery on the same track
width as the harvester because, as previously
mentioned, this machine is difficult to alter.
Unfortunately, the harvester is probably the
machine with the widest track, and with
current designs this will mean a primary
track width of around 3 m for all vehicles
and implements. This is common practice
in Australia (Fig. 16.6), where there may be
less need to drive on highways and where
rural areas have relatively low population
densities. In Europe and other parts of the
world with high population densities and
often-narrow roads, much greater difficulties
are likely. However, because no-tillage
reduces the number of field operations and
future spray vehicles may have ‘on the
move’ variable track widths, the extent of
the problem should diminish considerably.
It may only be the harvester and sowing
machine and associated tractor that have
the 3 m track setting on the road. The advantage
of this system is that there are few constraints
in terms of primary implement
widths. With very wide machines, some
means of extending the harvester’s unloading
auger may be needed to ensure that
the transport unit can be reached in the
adjacent traffic lane.
A further alternative similar to ‘twintrack’
for smaller farms is for the harvester
Controlled-traffic Farming 247
Fig. 16.6. Example of an Australian system with a 9 m primary module and a 3 m primary track width
(Webb et al., 2000).
to span between the same wheels of adjacent
tractor passes, as shown in Fig. 16.7. The
basis for this is:
This system potentially introduces a
large number of wheel tracks, but some of
these may only be used once a year for crop
sowing and most could be sown, as
described later.
So far, we have dealt primarily with the
systems used for small-grain crops, but the
principles of no-tillage can be applied equally
to most other crops. Although little research
has been done on no-tillage for vegetable
crops, improved potential may exist within
CTF systems, as discussed later.
Field layout and system management
Orientation and layout of controlled traffic
wheel ways are all part of the planning
process, and each individual area or block
of land needs to be considered independently.
Detailed field maps are an essential
part of this planning, by measurements,
historical records or aerial photographs.
Topographic data are also valuable, particularly
on farms with significant slopes.
Changes in soil type across a property are
likely to be of lesser significance than with
random traffic systems, but it will still be
useful to know these boundaries, particularly
with respect to drainage. With regard
to drainage, it is essential that any installed
drainage systems are operating properly or
problems corrected before installing a CTF
system. This is also true for soil structural
remediation. If inspection reveals a pan
layer, fissuring of the profile should be
attempted according to the guidelines suggested
by Spoor et al. (2003).
The principal aspects to consider in
any CTF layout are:
● Orientation of permanent wheel ways
in relation to:
■ length of run;
■ slope and water movement;
248 W.C.T. Chamen
Fig. 16.7. A controlled traffic machinery system for small farms. The 1.5 m primary track width is
spaced at 1.5 m intervals and thus any pair of wheel tracks can be used by all equipment other than
the harvester.
Primary implement width = harvester
track width
Primary track width = harvester
track
width/2
Harvester cutting width = harvester
track width
× 1.5
Chemical application width = any multiple
of
primary
implement
width
■ field shape and short rows;
■ extraneous objects (trees, pylons,
ponds, etc.);
■ field drainage system.
● Wheel-way management and field
access.
Orientation of permanent wheel ways
In most situations the longest length of the
area being considered is chosen for the orientation
because this improves field efficiency
by reducing the number of end turns. The
length of run that this creates must also be
considered in respect of any significant field
slope. Although water infiltration on the
soil ‘beds’ is likely to be improved significantly
compared with traditionally managed
fields, water will still tend to run along
and erode the wheel ways, particularly if
they run uninterrupted over long distances
and are orientated up and down slopes. In
Australia, where CTF is widely practised
and where rainfall events can be very heavy,
orientation of operations has become more
flexible with CTF. Both up and down and
across the slope can work, whereas with
random traffic across-slope or contour layouts
predominate.
CTF orientation must also consider the
presence of any drainage system, and particularly
one that involves mole channels.
The latter will run predominantly up and
down slopes and the aim with a controlled
traffic system is to run parallel to them. The
danger with repeated wheeling across the
mole channels is that they may collapse
prematurely. Running parallel to the moles
will mean crossing the drains themselves,
but it is unlikely that these will be damaged,
partly due to their depth but also because
they are often backfilled with gravel. If the
wheel ways run parallel to the mole channels,
although there is a danger that some
will be coincident with and may damage
them, the overall effect on the drainage system
within a field is likely to be minimal.
Running parallel will also ensure that the
mole channels can be redrawn without
complete disruption of the wheel ways.
For more information on drainage systems,
see Spoor (1994).
A similar approach is adopted with a
row of pylons going across a field; in this
case, they may be used for the orientation
and as a line to set up the first wheel tracks.
Unlucky indeed would be the farmer
who has both a drainage system and pylons
with completely different orientations! The
compromise would have to be with the
pylons. Experience with either drainage
systems or field ‘infrastructure’ is limited,
because CTF has yet to be adopted in areas
where these situations occur extensively.
Wheel-way management
The potential for wheel-way erosion can be
countered in a number of ways. As a first
principle, the wheel ways need active management
from the outset; they cannot be
allowed to sink or rut differentially. They
should be filled as required by drawing in
soil from the surrounding area, particularly
in the early days of establishment, and particularly
if the soil has been deep-loosened
recently. Within a tillage regime, these recommendations
could be met coincidentally
during the creation of a false seedbed for
weeds. However, in the context of no-tillage,
a customized narrow unit (Fig. 16.8) might
be used if rutting or plastic flow of soil out
of the wheel ways has occurred. This implement
should not be used too frequently, however,
as the edges of the beds may become
rounded and cause uneven sowing depth.
If weed or erosion pressures on bare
soil become unacceptable or, due to machinery
constraints, the wheel tracks take up a
large proportion of the area, crop may be
established within them (in general, this
applies only to those tracks that will not be
used after crop sowing). The roots of plants
established in these tracks will often explore
laterally and find their way into the main
crop bed. As a result and although they perform
less well, they do mature in unison
with and add significantly to the main crop
yield. This is not the case for sown wheel
ways that are used subsequently for crop
management. In these the plants are often
Controlled-traffic Farming 249
dwarfed by repeated wheeling and are late
to mature. Where wheel ways are sown
within a narrowly spaced crop (300 mm or
less), the row spacing may be altered slightly,
as illustrated in Fig. 16.9. The openers will
need to be set very specifically to deal with
this situation and the wear rate on them is
likely to be higher. To date there is limited
experience with this technique and growers
will need to use some field experimentation
initially, but this technique has the
added advantage of temporarily marking
the wheel ways.
In some instances, further active management
of the wheel ways might be needed
on slopes to ensure that water gathered
within them does not reach erosive potential.
This could be achieved by introducing diagonal
channels at regular intervals, which
divert water into the beds alongside.
The second principle of wheel-way
management is to avoid water standing in
or flowing along them. To a large extent, the
first of these problems can be avoided by
attending to active management, but low
spots in the field or areas of poor natural
drainage can also create this situation. Orientation
should aim to avoid low spots, but
this will not always be possible and an alternative
in the form of modifying the wheelway
edges, as described above, may need to
be introduced.
Wheel-way erosion may also be reduced
by a buffer strip part-way downslope.
250 W.C.T. Chamen
Fig. 16.8. Rolling maintenance tool used to deal with plastic flow of soil out of the wheel ways. This
would not normally be used on more than an annual basis (J. Grant, 2001, personal communication).
Fig. 16.9. Example of how a cereal crop might be sown on a wheel way. The nominal 250 mm
spacing is modified to 400/175 mm to encourage roots of the plants in the wheel way to access the
adjacent bed.
This might also provide an area for beneficial
insects and, if sited correctly, address
‘short row’ issues.
Guidance systems
Fundamental to any controlled-traffic farming
system is a means of ensuring that the
wheel ways are not only orientated but also
positioned correctly at the outset. Traditionally,
positioning has been achieved with
machine-mounted hardware that provides
an adjacent parallel marking line offset by
the required distance. The driver then uses
this line on the next pass to position the
machinery correctly. This works well with
modest machinery widths but, when these
approach 10 m or more, the size, strength
and durability of the equipment become a
significant factor. Offset loads can also be a
problem if the marker engages with the soil,
and maintenance costs can also be high. It is
an even greater problem under no-tillage
because the marker has to make a visible
line in untilled and often residue-covered
soil, and this is difficult. Markers have relatively
low precision and introduce errors
that are cumulative pass to pass. An alternative,
but still with cumulative errors and
poor precision, is to place a closed-circuit
video camera on the extremity of the implement,
with pictures relayed to a screen in
the driver’s cabin. This requires that the
driver continuously monitor the screen to
keep the machinery on course, as he or she
would with a marked line.
An increasingly available and attractive
alternative is electronic systems based
on a differential global positioning system
(DGPS) using satellite signals. There is a
wide range of available costs, depending
upon the degree of accuracy delivered.
With CTF systems, an accuracy of ± 3 cm is
desirable, with a peak error of ± 5 cm if
wide-row crop operations are planned.
Such systems can also be coupled directly
to the vehicle’s steering to provide autosteer
capability for both straight-line and
curved parallel tracking. Automatic steering
allows drivers to concentrate on the
implement operation, relieves them of the
constant stress of driving to a mark and also
avoids excessive steering corrections, which
can adversely affect machinery operation. A
further advantage, particularly with wide
equipment, is that any pass can be driven in
any sequence, because the positioning is
absolute, since it does not rely on a mark
from the previous pass. Drivers can skip
every other pass, for example. This makes
turning at the end easier and has the added
advantage that field completion can be at
the start point, which is normally the point
of field access.
It is also important to note that the
implement lateral offset feature found with
a number of satellite guidance systems cannot
be used with CTF. This feature compensates
for an implement that does not trail
centrally behind the tractor by shifting the
tractor appropriately on adjacent passes. If
this were used with CTF, it would move the
vehicle off the permanent wheel ways. Any
misalignment in a CTF system must therefore
be dealt with physically on the tractor
or implement and this can create a significant
challenge on side slopes. Trailed
equipment may need some wheel steer to
overcome this problem.
Economics
There are a number of ways in which the
economics of CTF systems can be assessed
and all will give different answers. Every
property, circumstance and range of machinery
will be unique and the economics of
change will be very specific. The aim in this
chapter, therefore, will be to establish the
principles and the cost/revenue centres
rather than entering into detailed cost analyses
that provide only a single hypothetical
solution. This approach also concentrates
on the transition from no-tillage seeding in
the presence of random traffic to a similar
but controlled traffic system.
Economics centre on:
● Planning and transition costs and their
timescale.
● Fixed and variable costs of the CTF
system employed.
Controlled-traffic Farming 251
● Change in output.
● Management costs.
Transition costs and timescale for
change to CTF
Planning is the key to minimizing costs.
And yet the cost of planning itself is difficult
to quantify. A typical consultancy fee
for CTF conversion in Australia is around
US$75 per hour. There will, however, be
many growers who will study the subject
carefully and put a plan together themselves,
the costs of which will be absorbed
within normal overheads. But serious consideration
should be given to employing the
services of experts to determine the most
efficient field layouts. Changing a layout
after installation is not an attractive proposition
and is very wasteful of time and
resources, as well as resulting in a loss in
productivity.
The planning process will involve taking
stock of existing farm equipment and
how much it can be applied within the new
regime. A clear picture of the new CTF cropping
and machinery regime needs to be
clearly identified at this stage before transition
costs can be estimated. The transition
costs fall into three main categories: (i) those
associated with changing the implements or
machines; (ii) those associated with changing
wheel-track settings; and (iii) those
associated with guidance:
1. Changing machinery might include
buying new, as well as discarding old equipment.
If a change to no-tillage is being made
at the same time as adoption of CTF, the
equipment requiring attention will be greater,
but an opportunity exists to integrate the
full range rather than just parts. With CTF,
the no-tillage drill will experience lower
penetration and draught forces and as a
result there will be lower power demands
on the tractor, so some longer-term savings
may be possible. Centralization of the harvester
cutting platform may also be necessary
because many are offset to assist unloading.
The other main aspect to consider is the
matching of implement widths, on the one
hand, and wheel-track settings, on the other.
2. The cost of changing wheel tracks may
be in the range US$750 to US$4000 (Webb
et al., 2000) and reflects considerable diversity
in machine designs, axle configurations
and wheel equipment. This cost will also
vary considerably depending upon the type
of system adopted, for example single- or
twin-track, as described earlier. For singletrack
systems, the cost is likely to be greater
because all equipment will probably have
to be matched to the wider track setting of
the harvester. Such conversions are now
available for some tractors, with total costs
for front and rear axles being in the region
of US$10,000. Most other equipment can be
modified locally or in the farm workshop.
For twin-track systems, the costs may be
confined to the labour required to alter the
position of rims on centres or swapping
wheels from side to side, for example.
3. Costs for guidance systems can be as little
as the time required to make up marker
arms from existing farm equipment to
around US$50,000 for a satellite system
delivering auto-steer with a mean offset
error of around ± 3 cm. The market and
therefore the cost structure for these satellitebased
systems is changing rapidly and to
such an extent that the full cost of the system
may not necessarily be attributable only
to conversion to CTF. Many farmers are
now purchasing these systems within
conventional practice as a means of improving
the accuracy of their operations, as
well as establishing tramlines for chemical
applications.
Not only does the latter give greater
flexibility, but it also precludes the need to
establish marks within the crop. Traditionally
these have been installed by special
equipment on the drill that leaves lines
unsown at the required intervals.
To introduce CTF, an existing system
might be upgraded from perhaps ± 25 cm
manual to ± 3 cm auto-steer. The additional
cost of this would be in the region of
US$17,000.
The timescale for change will depend
on the investment that has been calculated;
252 W.C.T. Chamen
the greater the investment, the shorter
should be the timescale. This is because the
greatest benefits will only be realized when
a complete CTF system is in place. These
benefits are dealt with in the section on
outputs.
Fixed and variable costs
Fixed costs are generally considered to be
regular labour, machinery, rent and general
overheads, while chemicals, seeds, fuel,
wearing parts, contractors and casual labour
are considered to be variable (Nix, 2001).
With CTF, we would expect the main
impact to be a lowering of fixed costs, and
particularly those related to labour and
machinery. The marginal labour benefit
from CTF will be less than but additional to
the marginal labour benefit from changing
to no-tillage in the first place.
Although it would be easy to attribute
CTF with improvements in field efficiency
due to better guidance, this can now be
achieved equally within conventional practice
using ‘tramline’ systems on drills or
through satellite guidance, and is therefore
not considered as a CTF benefit. The main
impact of CTF on labour in a no-tillage
system will be a reduced demand during
drilling, which could be slightly faster (conditions
permitting) as a result of lower
draught forces on the drill. Unless a contractor
is employed for this task, the farmer is
only likely to experience a timeliness benefit
in the short term. In the longer term it may
be possible to increase the land farmed with
a given labour force or lose some labour
costs if several are employed during drilling.
Changes in variable costs centre on
seeds, fuel, wearing parts and chemicals, all
of which should be reduced. Typically,
power demands for drilling at any particular
speed are reduced by up to 25%, including
the lower rolling resistance that can be
attributed to working on the permanent
wheel ways rather than on the crop bed.
Due to the improved soil conditions, lower
seed rates may be possible with less risk,
although this issue should also be handled
by improving the drilling methodology
rather than relying on CTF alone to make up
for deficiencies in drilling equipment or
technique. Savings on wearing parts are more
difficult to predict but will increase the
longer the soil is under no-tillage.
Chemical costs are likely to be reduced
principally through greater precision and
the ability to inter-row band-spray with nonselective
chemicals while simultaneously
applying selectively to the crop row. Although
such a system is not exclusive to CTF,
the well-maintained wheel ways offer greater
potential. If one considers that the cost of
protection chemicals for wheat grown in a
temperate region approaches 50% of the
total cost of seed, fertilizer and spray (Nix,
2001), then any saving on these chemicals
is likely to have significant cost implications.
Equally, a reduction in chemical inputs,
or at least input of less environmentally
damaging chemicals, is an added benefit.
We may also presume that fertilizers applied
in a CTF regime will be more efficiently
utilized and, although this may not be a cost
saving to the farm, it will result in an
improved yield (discussed below) and a
lower risk of off-farm pollution of watercourses.
Change in output
Reviewing research undertaken over the
past 30–40 years on soil compaction with
17 different crops showed that yields under
CTF in both tilled and non-tilled conditions
had increased in the range 9–16% compared
with random traffic. The less extensive data
quoted for no-tillage systems suggest a more
modest level of improvement; a safe figure
may be around 10%. Soil type, cultural
practices, crop rotations and the percentage
area of land taken up by permanent wheel
tracks will obviously moderate these percentages,
and the crop row spacing will further
influence the effect. To determine what
happens in practice, each individual case
needs to be considered and the following
suggests an approach that might be taken.
Taking the 8 m system considered earlier
and a close-spaced row crop such as
Controlled-traffic Farming 253
wheat (250 mm in this case), the following
is assumed to apply:
Assuming that crop yield is improved by
10% only on the non-trafficked area and
that the harvester will have wheels around
750 mm wide, the number of rows affected
by wheels will be 3 × 2 × 4 = 24 rows out of a
total of 96. There will be no improvement in
yield on these rows and therefore the net
improvement will be 7.5%. This is actually
a conservative estimate because conventional
systems usually have tramlines where at
least two rows will be missing within a
24 m width.
In-field management costs
The main ongoing management cost to sustain
field operations is likely to be that associated
with the permanent wheel ways. As
indicated earlier, a customized small implement
(Fig. 16.8) may suffice for this task,
but within a no-tillage regime this represents
an additional pass, usually carried out after
harvest. Experience suggests that this may
be needed in the early years of conversion
and when any operation has to be carried
out in wet conditions. In some instances,
this may only be needed on the chemical
application wheel ways.
Summary of costs and returns
Table 16.1 provides an overview of the
aspects considered in the foregoing text and
attempts to quantify a number of the variables.
As stressed earlier and confirmed by
Uri (2000), the variables are so numerous
that any fully calculated example involving
conservation or no-tillage systems will only
provide a specific solution unique to a particular
situation. It is better, therefore, to
have the tools and a procedure to calculate
rather than to give a single answer.
The magnitude of these costs can be
put into context by examining some of the
benefits. A world price for wheat of US$100/t
and an average yield of 4 t/ha increased by
7.5% on 500 ha, equates to an additional
income of US$15,000 per annum. At 2001
prices, a 20% reduction in tractor size from
134 kW would give a saving of around
US$17,000. The net benefit from these two
items on 500 ha is US$32,000 at the end of
the first year.
Detailed analyses on a regional basis are
offered by a number of authors and the
reader is referred to these specific studies for
further information. Gaffney and Wilson
(2003), for example, suggest a net benefit of
US$15–25/ha for a change to CTF within a
no-tillage regime on a vertisol in Queensland,
while Mason et al. (1995) for the same scenario
in the South Burnett of Australia suggest
a net improvement of US$75/ha.
Summary of Controlled-traffic
Farming as a Complementary
Practice to No-tillage
1. Controlled-traffic farming (CTF) is a
crop production system in which the crop
zone and traffic lanes are distinctly and
permanently separated. In practice, it
requires:
a. use of the same wheel tracks for all
field operations;
b. all machines to have the same
wheel-track setting;
c. all implements to have a particular
span or multiple of it.
2. CTF relies on good guidance systems to
install and keep the permanent wheel ways
in the same place from year to year. The main
systems used to do this are:
a. physical markers, which provide a
means of positioning the next pass,
which, if integrated with seeding, may
be used to introduce guide rows for
later use;
b. closed-circuit television (CCTV)
video cameras with an associated display
in the driver’s cabin;
254 W.C.T. Chamen
Primary implement width = 8 m
Primary track width = 3 m
Chemicals applied at 24 m width
Two out of every three primary tracks
are sown
c. differential global positioning systems
using satellites;
d. automatic steering controlled by
the guidance system.
3. CTF should liberate the full potential
of no-tillage seeding by avoiding soil
compaction damage in the cropping zone.
This is likely to result in:
a. improved crop yields from the
outset;
b. better nutrient use efficiency
achieved through greater root proliferation;
c. improved soil porosity, which provides
better water infiltration, drainage
and gaseous exchange;
d. reduced threat of denitrification,
particularly in the presence of organic
residues;
e. lower draught forces and wear on
seed openers;
f. reduced labour and fuel inputs,
particularly during seeding operations;
g. lower power demand for drilling,
allowing a smaller tractor to be used for
a given output;
h. more reliable and consistent operation
of seed openers in a wider range of
conditions and soils;
i. the potential for a wider range of
crops to be grown with no-tillage.
4. In other situations, many of these
advantages will come from the change to
no-tillage, which reduces, but seldom eliminates,
the additional gains to be had from
CTF. In most cases, combining CTF and
no-tillage achieves a greater potential from
no-tillage [Eds].
Controlled-traffic Farming 255
Factor/variable Costs, US$ Savings/benefits, %
Consultancy for CTF field layout 75/h
Drill price (from Uri, 2000) 6,400 11
DGPS guidance with ± 25 cm pass-to-pass accuracy 2,400a
DGPS guidance upgrade from ± 25 cm to ± 3 cm accuracyc 15,400b
DGPS guidance to ± 3 cm with automatic steeringc 5,400–10,200
Axle conversions to 3 m:
Tractors – per tractor with full warranty 750–4,000
Drill, chasers or trailers, per item 5,000–7,000
Self-propelled chemical applicators with full warranty 17–25d
(Not needed if tractor mounted. Also, many North
American special-purpose vehicles are now available
with 3 m axles)
5d
Lower-power tractor for hauling drill 20
Labour 15
20
Variable costs: 10
Seed
Fuel 3/ha 7.5
Wearing parts – soil-engaging elements
Chemicals
Wheel-way maintenance
Crop yield
aAdditional cost to the ± 25 cm system, i.e. total cost would be 6400 + 2400 = US$8800.
bAdditional cost to the ± 3 cm system, i.e. total cost would be 8800 + 15,400 = US$24,200.
cThis option has an annual US$1330 correction signal fee.
dTractor power or labour reduction, not both – see ‘Fixed and variable costs’ in main text.
Table 16.1. Factors and variables that impact on the economics of changing from a random traffic to a
controlled traffic no-tillage seeding system, their likely magnitude and level following transition.
5. CTF allows farmers to anticipate greater
levels of precision in all operations so that
they may:
a. increase the flexibility and effectiveness
of weed control;
b. spray the crop row and inter-row
independently;
c. use non-selective chemicals in the
inter-row;
d. perhaps position and manage residues
to allow their manipulation to
greater benefit.
6. The cost of converting to CTF need not
be great, providing it is carefully designed
and part of the forward-planning process. If
properly planned, the benefits are likely to
far outweigh the costs.
7. There are a number of ways that CTF
can be achieved and all will vary in terms
of cost. Field layout is a particularly important
aspect because it needs to account for
field drainage, slope, operating efficiency
and permanent obstacles.
8. Permanent wheel tracks within a CTF
regime need to be managed to ensure optimum
performance. Management is likely to
include:
a. regular infilling, preferably as an
integral part of normal field operations;
b. engineering their drainage down
slopes and in low areas;
c. sowing with crop in particular circumstances
and in a particular way.
9. Additional environmental benefits can
be achieved by no-tillage in combination
with CTF.
256 W.C.T. Chamen
17 Reduced Environmental Emissions
and Carbon Sequestration
Don C. Reicosky and Keith E. Saxton
While tillage agriculture contributes
significant greenhouse gases detrimental
to the atmosphere, no-tillage agriculture will
reduce them by both storing new SOM and
reducing the oxidation of existing SOM.
Introduction
Agriculture affects the condition of the
environment in many ways, including
impacts on global warming through the
production of ‘greenhouse gases’, such as
CO2 (Robertson et al., 2000). In 2004, the
US Environmental Protection Agency (EPA)
estimated that agriculture contributed
approximately 7% of the US greenhouse
gas emissions (in carbon equivalents, CE),
primarily as methane (CH4) and nitrous
oxide (N2O). While agriculture represents a
small but relevant source of greenhouse gas
emissions, it has the potential, with new
practices, to also act as a sink by storing and
sequestering CO2 from the atmosphere in
the form of soil carbon (Lal, 1999). Estimates
of the potential for agricultural
conservation practices to enhance soil carbon
storage range from 154 to 368 million
metric tons (MMTCE), which compare to
the 345 MMTCE of reduction proposed for
the USA under the Kyoto Protocol (Lal
et al., 1998). Thus, agricultural systems can
be manipulated for the dual benefits of
reducing greenhouse gas emissions and
enhancing carbon sequestration. The influence
of agricultural production systems on
greenhouse gas generation and emission is
of interest as it may affect potential global
climate change. Agricultural ecosystems can
play a significant role in production and
consumption of greenhouse gases, specifically,
CO2.
Conservation tillage reduces the extent,
frequency and magnitude of mechanical disturbance
caused by the mouldboard plough,
reduces the air-filled macropores and slows
the rate of carbon oxidation. Any effort to
decrease tillage intensity and maximize residue
return should result in carbon sequestration
for enhanced environmental quality.
Tillage-induced Carbon Dioxide
Emissions
Tillage or soil preparation has been an integral
part of traditional agricultural production.
Tillage is also a principal agent
resulting in soil perturbation and subsequent
modification of the soil structure
with soil degradation. Intensive tillage can
adversely affect soil structure and cause
excessive breakdown of aggregates, leading
© FAO and CAB International 2007. No-tillage Seeding in Conservation
Agriculture, 2nd edn. (eds C.J. Baker and K.E. Saxton) 257
to potential soil movement via erosion.
Intensive tillage causes soil degradation
through carbon loss and tillage-induced
greenhouse gas emissions, mainly CO2,
which have an impact on productive capacity
and environmental quality.
Intensive tillage decreases soil carbon.
The large gaseous losses of soil carbon following
mouldboard ploughing compared
with relatively small losses with no-tillage
have shown why crop production systems
using mouldboard ploughing have resulted
in decreased SOM and why no-tillage or
direct-seeding crop production systems are
stopping or reversing that trend (Reicosky
and Lindstrom, 1993). Reversing the trend
of decreased soil carbon with less tillage
intensity will be beneficial to agriculture as
well as the global population through better
control of the global carbon balance
(Reicosky, 1998).
Emission measurements
The tillage studies reported in this chapter
were conducted in west central Minnesota,
USA, on rich soils high in soil organic carbon
(Reicosky and Lindstrom, 1993, 1995;
Reicosky, 1997, 1998). The CO2 flux from
the tilled surfaces in these studies was measured
using a large, portable chamber,
described by Reicosky (1990) and Reicosky
et al. (1990), in the same manner as
described by Reicosky and Lindstrom (1993)
and Reicosky (1997, 1998). Measurements of
CO2 flux were generally initiated within
1 minute after the tillage pass and continued
for various times. The CO2 flux from the
soil surface was measured using the large,
portable chamber described by Reicosky and
Lindstrom (1993).
Briefly, the chamber, with mixing fans
running, was placed over the tilled surface
or the no-tilled surface, the chamber lowered
and data collected for 1 s intervals for a
total of 60 s to determine the rate of CO2 and
water vapour increases inside the chamber.
The chamber was then raised, calculations
completed and the results stored on computer
floppy disk.
The data included the time, plot identification,
solar radiation, photosynthetically
active radiation, air temperature, wet bulb
temperature, output of the infrared gas
analyser measuring CO2 and water vapour
concentrations in the same airstream. After
the appropriate lag and mixing times, data
for a 30 s calculation window were selected
to convert the volume concentrations of
water vapour and CO2 to a mass basis and
then regressed as a function of time using
linear and quadratic equations to estimate
the gas fluxes. These fluxes represent the
rate of CO2 and water vapour increase
within the chamber from a unit horizontal
land area as differentiated from a soil surface
basis caused by differences in soil
roughness. Only treatment differences in
respect of tillage methods, tillage type or
experimental objectives are described, with
the results.
Tillage and residue effects
Recent studies, involving the dynamic
chamber described above, various tillage
methods and associated incorporation of
residues in the field, indicated major carbon
losses immediately following intensive
tillage (Reicosky and Lindstrom, 1993, 1995).
The mouldboard plough had the roughest
soil surface, the highest initial CO2 flux and
maintained the highest flux throughout the
19-day study. High initial CO2 fluxes were
more closely related to the depth of soil disturbance
that resulted in a rougher surface
and larger voids than to residue incorporation.
Lower CO2 fluxes were caused by tillage
associated with low soil disturbance
and small voids, with no-tillage having the
least amount of CO2 loss during 19 days.
The large gaseous losses of soil carbon
following mouldboard ploughing (MP)
compared with relatively small losses with
no-tillage (NT) or direct seeding have
shown why crop production systems using
mouldboard ploughing have decreased
SOM and why no-tillage or direct-seeding
crop production systems are stopping
or reversing that trend. The short-term
258 D.C. Reicosky and K.E. Saxton
cumulative CO2 loss was related to the soil
volume disturbed by the tillage tools. Lower
CO2 fluxes were caused by tillage associated
with low soil disturbance and small
voids, with no-tillage having the least
amount of CO2 loss during 19 days. Similarly,
Ellert and Janzen (1999) used a single
pass with a heavy-duty cultivator that was
relatively shallow and a small dynamic
chamber to show that fluxes from 0.6 hours
after tillage were two- to fourfold above the
pre-tillage values and rapidly declined
within 24 hours of cultivation. They concluded
that short-term influences on tillage
and soil carbon loss were small under
semi-arid conditions, in agreement with
Franzluebbers et al. (1995a, b).
On the other hand, Reicosky and
Lindstrom (1993) concluded that intensive
tillage methods, especially mouldboard
ploughing to 0.25 m deep, affected this initial
soil flux differently and suggested that
improved soil management techniques can
minimize the agricultural impact on global
CO2 increase. Reicosky (2001b) further
demonstrated the effects of secondary tillage
methods and post-tillage compaction in
decreasing the tillage-induced flux. Apparently,
severe soil compaction decreased
porosity and limited the CO2 flux after
plough tillage to that of the no-tillage
treatment.
This concept was further explored
when Reicosky (1998) determined the
impact of strip tillage methods on CO2 loss
after five different strip tillage tools were
used in row-crop production and no-tillage.
The highest CO2 fluxes were from mouldboard
plough and subsoil shank tillage.
Fluxes from both slowly declined as the soil
dried. The least CO2 flux was measured
from the no-tillage treatment. The other
forms of strip tillage were intermediate,
with only a small amount of CO2 detected
immediately after the tillage operation.
These results suggested that the CO2 fluxes
appeared to be directly and linearly related
to the volume of soil disturbed. Intensive
tillage fractured a larger depth and volume
of soil and increased aggregate surface area
available for gas exchange, which contributed
to the vertical gas flux. Narrower and
shallower soil disturbance caused less CO2
loss, suggesting that the volume of soil disturbed
must be minimized to reduce carbon
loss and the impact on soil and air quality.
The results also suggest that the environmental
benefits and carbon storage of strip
tillage compared with broad-area tillage
need to be considered in soil management
decisions.
Reicosky (1997) reported that average
short-term CO2 losses 5 hours after the use
of four conservation tillage tools were only
31% of that of the mouldboard plough. The
mouldboard plough lost 13.8 times as much
CO2 as the soil area not tilled, while different
conservation tillage tools lost an average
of only 4.3 times. The benefits of residues
on the soil surface to minimize erosion and
smaller CO2 loss following conservation
tillage tools are significant and suggest
progress in developing conservation tillage
tools that can enhance soil carbon management.
Conservation tillage reduces the extent,
frequency and magnitude of mechanical disturbance
caused by the mouldboard plough
and reduces the large air-filled soil pores to
slow the rate of gas exchange and carbon
oxidation.
Reicosky et al. (2002) have shown that
removal of maize stover as silage for 30
years of continuous maize, compared with
returning the residue and removing only the
grain, resulted in no difference in the soil
carbon content after 30 years of mouldboard
ploughing. Fertility level had no observable
effect on CO2 losses. The tillage-induced
CO2 flux data represented the cumulative
gas exchange for 24 h for all treatments.
The pre-tillage CO2 flux from the same
area not tilled averaged 0.29 g CO2/m2/h for
the high-fertility plots at the start of measurements.
This contrasts with the largest
cumulative flux after tillage of 45 g CO2/
m2/h on a low-fertility grain plot. The CO2
flux showed a relatively large initial flux
immediately after tillage and then rapidly
decreased 4 to 5 hours after tillage. The CO2
flux decrease continued as the soil lost CO2
and dried out to 24 hours, when values
were lower but still substantially higher
than those from the no-tillage treatment.
The flux 24 h after tillage on the same plots
Reduced Environmental Emissions 259
above was approximately 3 g CO2/m2/h,
considerably higher than the pre-tillage
value.
The temporal trend was similar for all
treatments, suggesting that the physical
release controlled the flux rather than the
imposed experimental treatments. The consistency
of the C : N ratio across all four
treatments suggests little effect of residue
removal or addition and that mouldboard
ploughing masked the effects of residue
removal as silage or grain removal and
above-ground stover returned. Intensive
tillage with the mouldboard plough overshadowed
any residue management aspects
and resulted in essentially the same lower
carbon content at the end of 30 years. The
results suggest that intensive tillage with a
mouldboard plough may overshadow any
beneficial effect of residue management
(return or removal) that might be considered
in a cropping system.
Strip tillage and no-tillage effects on
CO2 loss
The impact of broad-area tillage on soil carbon
and CO2 loss suggests possible improvements
with mulch between the rows and less
intensive strip tillage to prepare a narrow
seedbed, as well as no-tillage. Reicosky
(1998) quantified short-term tillage-induced
CO2 loss after the use of strip tillage tools
and no-tillage. Various strip tillage tools,
spaced at 76 cm, were used and gas exchange
measured with a large portable chamber.
Gas exchange was measured regularly for
6 hours and then at 24 and 48 hours.
No-tillage had the lowest CO2 flux during
the study and mouldboard ploughing had
the highest immediately after tillage, which
declined as the soil dried. Other forms of
strip tillage had an initial flush related to
tillage intensity, which was intermediate
between these extremes, with both the
5 and 24 hour cumulative losses related
to the soil volume disturbed by the tillage
tool.
Reducing the volume of soil disturbed
by tillage should enhance soil and air
quality by increasing soil carbon content.
These results suggest that soil and environmental
benefits of strip tillage should be
considered in soil management decisions.
Limited tillage can be beneficial and do
much to improve soil and air quality, minimize
runoff to enhance water quality and
minimize the greenhouse effect. The energy
savings represent an additional economic
benefit associated with less disturbance of
the soil. The results suggest environmental
benefits of strip tillage over broad-area tillage,
which need to be considered when
making soil management decisions.
The CO2 flux as a function of time for
each tillage method for the first 5 hours
showed that mouldboard ploughing had the
highest flux, which was as large as 35 g
CO2/m2/h and then rapidly declined to 6 g
CO2/m2/h 5 hours after tillage. The second
largest CO2 flux was 16 g CO2/m2/h following
subsoil shanks, which also slowly
declined. The least CO2 flux was measured
from the no-tillage treatment, with an average
flux of 0.2 g CO2/m2/h for the 5 hour
period. Other forms of strip tillage were
intermediate and only a small amount of
CO2 was detected immediately after some
tillage operations, which ranged from 3 to
8 g CO2/m2/h and gradually declined to
approach no-tillage values within 5 hours.
These results suggest a direct relationship
between the magnitude of the CO2 flux that
appears to be related to the volume of soil
disturbed.
The cumulative CO2 losses calculated
by integrating the flux as a function of time
for both 5 and 24 h periods showed similar
trends. The values for 24 hours may be subject
to error due to the long time between
the last two measurements and tillageinduced
drying, which may have caused
the tilled treatments to dry out faster than
the no-tillage treatments. The cumulative
flux for the first 5 hours after tillage for
mouldboard ploughing was 59.8 g CO2/m2,
decreasing to 31.7 g CO2/m2 for the subsoil
shank to a low of 1.4 g CO2/m2 for the notillage
treatment. The strip tillage methods
had slightly more CO2 loss than no-tillage.
Similarly, the cumulative data for the
24 h period reflect the same trend, the maximum
release by mouldboard ploughing,
260 D.C. Reicosky and K.E. Saxton
159.7 g CO2/m2, decreasing to 7.2 g CO2/m2
for no-tillage. The other forms of strip tillage
were intermediate between these, which
paralleled the 5 hour data. The results suggest
that cumulative CO2 loss was directly
related to the soil volume disturbed by the
tillage tool. The narrower and shallower
soil disturbance caused less CO2 loss.
The cross-sectional areas of the soil disturbed
by the tillage were estimated from
field measurements drawn to scale, using
graphical techniques. The drawings were
then cut out and run through an area meter.
The cumulative CO2 fluxes for 24 hours
were then plotted as a function of these soil
areas disturbed and showed a nearly linear
relationship between the 24 hour cumulative
CO2 flux and the soil volume disturbed by
tillage. These results suggest that intensive
tillage fractured a larger depth and volume
of soil and increased aggregate surface area
available for gas exchange. This increased
soil porosity and area for gas exchange contributed
to the vertical flux, which was largest
following mouldboard ploughing.
The results of short-term CO2 loss from
the strip tillage study for row crops suggest
that, to minimize the impact of tillage on
soil and air quality, the volume of soil disturbed
must be minimized. Tilling the soil
volume necessary to get an effective seedbed
and leaving the remainder of the soil
protected and undisturbed to conserve
water and carbon to minimize soil erosion
and CO2 loss should be the preferred strategy.
Limited tillage can be beneficial and
do much to improve soil and air quality,
minimize runoff to enhance water quality
and minimize the greenhouse effect. The
energy savings represent an additional economic
benefit associated with less disturbance
of the soil (West and Marland, 2002;
Lal, 2004). The results suggest that the
environmental benefits of strip tillage over
broad-area tillage need to be considered
when making soil and residue management
decisions.
The concept that each soil has a finite
carbon storage capacity is being revisited.
This has important implications for soil
productivity and the potential of using soil
to enhance soil carbon storage and reduce
greenhouse gases in the atmosphere. Most
agricultural and degraded soils can provide
significant potential sinks for atmospheric
CO2. However, soil carbon accumulation
does not continue to increase with time
with increasing carbon inputs but reaches
an upper limit or carbon saturation level,
which governs the ultimate limit of the soil
carbon sink (Goh, 2004). The relation
between no-tillage and conservation tillage
in the way they affect soil carbon stocks is
open to further debate and definition of
carbon pools.
The relationship between tillageinduced
changes in soil structure and subsequent
effect on carbon loss was reviewed
by Six et al. (2002) within the framework of
a newly proposed soil C-saturation concept.
They differentiated SOM that is protected
against decomposition by various mechanisms
from that which is not protected and
discussed implications of changes in land
management for processes that affected carbon
release. This new model defined a soil
C-saturation capacity, or a maximum soil
carbon storage potential, determined by the
physicochemical properties of the soil, and
was differentiated from models that suggested
soil carbon stocks increased linearly
with carbon inputs. Presumably, this
carbon saturation capacity will be soil-,
climate- and management-specific. This
causes a change in the thinking about carbon
sequestration and that a soil-dependent
natural limit may exist in both natural and
managed systems.
Superimposed on this analysis is the
role of glomalin, a sticky substance produced
by fungal hyphae that helps glue soil
aggregates together (Nichols and Wright,
2004). No-tillage is one management practice
that has been successful in increasing
the hyphal fungi that produce glomalin.
The next researchable challenge will be to
determine if the carbon saturation and
glomalin over the entire profile in no-tillage
and conservation tillage systems are substantially
different. Presumably with less
tillage-induced breakdown of soil aggregates,
no-tillage may have an advantage
over other forms of conservation tillage. The
final answer awaits further research.
Reduced Environmental Emissions 261
Carbon Sequestration Using
No-tillage
Conservation agriculture is receiving much
global focus as an alternative to the use of
conventional tillage systems and as a means
to sequester soil organic carbon (SOC)
(Follett, 2001; Garcia-Torres et al., 2001).
Conservation agriculture can work under
many situations and is cost-effective from a
labour standpoint. More importantly, the
practices that sequester soil organic carbon
contribute to environmental quality and the
development of a sustainable agricultural
system. Tillage or other practices that destroy
SOM or cause loss and result in a net
decrease in soil organic carbon do not result
in a sustainable agriculture. Sustainable
agricultural systems involve those cultural
practices that increase productivity while
enhancing carbon sequestration. Crop residue
management, conservation tillage
(especially no-tillage), efficient management
of nutrients, precision farming, efficient
management of water and restoration
of degraded soils all contribute to a
sustainable agriculture.
Kern and Johnson (1993) calculated
that conversion of 76% of the cropland
planted in the USA to conservation tillage
could sequester as much as 286 to 468
MMTCE over 30 years and concluded that
US agriculture could become a net sink for
carbon. Lal (1997) provided a global estimate
for carbon sequestration from conversion
of conventional to conservation tillage
that was as high as 4900 MMTCE by 2020.
Combining economics of fuel cost reductions
and environmental benefits derived
by converting to conservation tillage are
positive first steps for agriculture towards
decreasing carbon emissions into the
atmosphere.
Soil tillage practices are of particular
significance for the carbon status of soils
because they affect carbon dynamics directly
and indirectly. Tillage practices that
invert or considerably disturb the surface
soil reduce soil organic carbon by increasing
decomposition and mineralization of
biomass due to increased aeration and mixing
plant residues into the soil, exposing
previously protected soil organic carbon in
soil aggregates to soil fauna, and by increasing
losses due to soil erosion (Lal, 1984,
1989; Dick et al., 1986a, b; Blevens and
Frye, 1993; Tisdall, 1996). Conversely,
long-term no-tillage or reduced tillage systems
increase soil organic carbon content of
the soil surface layer as a result of various
interacting factors, such as increased residue
return, less mixing and soil disturbance,
higher soil moisture content, reduced
surface soil temperature, proliferation of root
growth and biological activity and decreased
risks of soil erosion (Lal, 1989; Havlin et al.,
1990; Logan et al., 1991; Blevens and Frye,
1993; Lal et al., 1994a, b).
Cambardella and Elliott (1992) observed
for a loam soil that the soil organic carbon
content in the 0 to 20 cm depth was 3.1,
3.5, 3.7 and 4.2 kg/m2 for bare fallow,
stubble mulch, no-tillage and native sod,
respectively. They observed that tillage
practices can lead to losses of 40% or more
of the total soil organic carbon during a
period of 60 years. Edwards et al. (1992)
observed that conversion from mouldboard
plough tillage to no-tillage increased soil
organic carbon content in the 0 to 10 cm
layer from 10 g/kg to 15.5 g/kg in 10 years,
an increase of 56%. Lal et al. (1998) stated:
A summary of the available literature
indicates that the soil organic carbon
sequestration potential of conversion to
conservation tillage ranges from 0.1 to
0.5 metric tons ha−1 yr−1 for humid temperate
regions and from 0.05 to 0.2 metric tons
ha−1 yr−1 for semi arid and tropical regions.
They further estimated that the soil organic
carbon increase may continue over a period
of 25 to 50 years, depending on soil properties,
climate conditions and management.
Carbon sequestration in the soil has
benefits beyond removal of CO2 from the
atmosphere. No-tillage cropping reduces
fossil fuel use, reduces soil erosion and
enhances soil fertility and water-holding
capacity. Beneficial effects of conservation
tillage on soil organic carbon content,
however, may be short-lived if the soil is
ploughed, even after a long time under conservation
tillage (Gilley and Doran, 1997;
262 D.C. Reicosky and K.E. Saxton
Stockfisch et al., 1999). Stockfisch et al.
(1999) concluded that organic matter stratification
and accumulation as a result of
long-term minimum tillage were completely
lost by a single application of inversion
tillage in the course of a relatively mild
winter. Tillage accentuates carbon oxidation
by increasing soil aeration and soil residue
contact, and accelerates soil erosion by
increasing exposure to wind and rain
(Grant, 1997). Several experiments in North
America have shown more soil organic
carbon content in soils under conservation
tillage compared with plough-tillage seed
beds (Doran, 1980; Doran et al., 1987;
Rasmussen and Rohde, 1988; Havlin et al.,
1990; Tracy et al., 1990; Kern and Johnson,
1993; Lafond et al., 1994; Reicosky et al.,
1995).
Similar to the merits of no-tillage
reported in North America, Brazil and
Argentina (Lal, 2000; Sa et al., 2001), several
studies have reported a high potential
for soil organic carbon sequestration in
European soils. In an analysis of 17
European tillage experiments, Smith et al.
(1998) found that the average increase of
soil organic carbon, with a change from
conventional tillage to no-tillage, was 0.73 ±
0.39% per year and that soil organic carbon
may reach a new equilibrium in approximately
50 to 100 years. Analysis of some
long-term experiments in Canada (Dumanski
et al., 1998) indicated that soil organic carbon
can be sequestered for 25 to 30 years at
a rate of 50 to 75 g carbon/m2/year, depending
on the soil type in well-fertilized
Cherozem and Luvisol soils cropped continuously
to cereals and hay. Analysis of
these Canadian experiments focused on
crop rotations, as opposed to tillage, and is
unique in that it considered rates of carbon
sequestration with regard to soil type.
On a global basis, West and Post (2002)
suggested that soil carbon sequestration
rates with a change to no-tillage practices
can be expected to have a delayed response,
reach a peak sequestration rate in 5 to 10
years, and then decline to nearly 0 in 15 to
20 years, based on regression analysis. This
agrees with a review by Lal et al. (1998),
based on results from Franzluebbers and
Arshad (1996) showing that there may be
little or no increase in soil organic carbon in
the first 2 to 5 years after a change in management
practice, followed by a large increase in
the next 5 to 10 years. Campbell et al. (2001)
concluded that wheat rotation systems in
Canada will reach an equilibrium, following
a change to no-tillage, after 15 to 20
years, provided average weather conditions
remained constant. Lal et al. (1998) estimated
that rates of carbon sequestration
may continue over a period of 25 to 50
years. The different estimates of carbon
sequestration may be expected partly
based on different rotations and rotation
diversity.
Nitrogen Emissions
Cropping systems and nitrogen fertilization
affect plant biomass production, partially
controlling input of organic carbon to the
SOM stocks. Agriculture alters the terrestrial
nitrogen cycle as well. Through nitrogen
fertilization, annual cropping,
monocropping and improper water management,
nitrogen is more prone to being
lost to both ground- or surface water and the
atmosphere. N2O, a common emission from
agricultural soils, is a potent greenhouse gas
(310 times more potent than CO2), which
has increased its atmospheric concentration
by 15% during the past two centuries
(Mosier et al., 1998). Reductions can be
achieved through improved nitrogen management,
as well as with irrigation water
management, because N2O is generated
under both aerobic conditions (where nitrification
occurs) and anaerobic conditions
(where denitrification occurs) in the soil.
Due to the tightly coupled cycles of carbon
and nitrogen, changes in rates of carbon
sequestration and terrestrial ecosystems will
directly affect nitrogen turnover processes
in the soils and biosphere–atmosphere
exchange of gaseous nitrogenous compounds.
Some data suggest that increasing N2O emissions
may be closely linked to increasing
soil carbon sequestration (Mosier et al.,
1991; Vinther, 1992; McKenzie et al., 1998;
Reduced Environmental Emissions 263
Robertson et al., 2000). If no-tillage is a truly
viable management practice, it must mitigate
the overall impact of no-tillage adoption
by reducing the net global warming
potential determined by the fluxes of all the
greenhouse gases, including N2O and CH4.
Six et al. (2004) assessed potential
global warming mitigation with the adoption
of no-tillage in temperate regions, by
compiling all available data reporting differences
in fluxes of soil-derived C, N2O
and CH4 between conventional tillage and
no-tillage systems. Their analysis indicated
that, at least for the first decade, switching
from conventional tillage to no-tillage
would generate enhanced N2O emissions
for humid environments and somewhat
lower emissions for dry environments,
which would offset some of the potential
carbon sequestration gains; and that, after
20 years, N2O emissions would return to or
drop below conventional tillage fluxes.
They found that N2O emissions, with a high
global warming potential, drive much of the
trend in net global warming potential, suggesting
that improved nitrogen management
is essential to realize the full benefits
from carbon storage in the soil for the purposes
of global warming mitigation. They
suggested caution in the promotion of
no-tillage agriculture to reduce greenhouse
gas emissions and that the total radiative
forcing needs additional consideration
beyond just the benefit of carbon sequestration.
They suggested that it is critical to
investigate the long-term as well as shortterm
effects of various nitrogen management
strategies for long-term reduction of
N2O fluxes under no-tillage conditions.
These results suggest the need for more
basic research on N2O emissions during the
transition from conventional tillage to
no-tillage and after equilibrium conditions
have been achieved to adequately quantify
the carbon-offsetting effects in global
warming potential.
In Brazil, most, but not all, studies
indicate that the introduction of zone tillage
increases SOM (Bayer et al., 2000a, b;
Sa et al., 2001). Sisti et al. (2004) evaluated
changes in soil carbon in a 13-year
study comparing three different cropping
rotations under zone tillage and conservation
tillage in a clayey Oxisol soil sampled
to 100 cm. They found that, under a continuous
sequence of winter wheat and summer
soybean, the stock of soil carbon to
100 cm under zone tillage was not significantly
different from that under conservation
tillage. However, in rotations with a
vetch crop, soil carbon stocks were significantly
higher under zone tillage than under
conservation tillage. They concluded that
the contribution of nitrogen fixation by the
legume crop was the principal factor
responsible for the observed carbon accumulation
in the soil under zone tillage. The
results demonstrate the role of diverse crop
rotations, especially including legumes
supplying organic nitrogen under zone tillage,
in the accumulation of soil carbon. The
dynamic nature of the carbon : nitrogen
ratio may require additional organic nitrogen
to increase carbon sequestration at depth.
Sisti et al. (2004) found that much of the
nitrogen gain was at depths below the
plough layer, suggesting that most of the
accumulated soil carbon was derived from
crop root residues.
Further work in Brazil reflects the
importance of soil and plant management
effects on soil carbon and nitrogen losses to
1 m depth (Diekow et al., 2004). They evaluated
carbon and nitrogen losses during
a period of conventional cultivation that
followed on native grassland and 17-year
no-tillage cereal- and legume-based cropping
systems with different nitrogen fertilization
levels to increase carbon and nitrogen stocks.
With nitrogen fertilization, the carbon and
nitrogen stocks of the oat/maize rotation
were steady with time. However, they
found increased carbon and nitrogen stocks
due to higher residue input in the legumebased
cropping systems. The long-term
no-tillage legume-based cropping systems
and nitrogen fertilization improved soil carbon
and nitrogen stocks of the previously
cultivated land to the original values
of the native grassland. Nitrogen and legume
residues in a rotation were more effective for
building soil carbon stocks than inorganic
nitrogen from fertilizer applied to the grass
crop in the rotation. In addition, legume
264 D.C. Reicosky and K.E. Saxton
nitrogen does not require the cost of using
fossil fuel to manufacture nitrogen fertilizer.
The dominant soil change took place
in the surface layer; however, deeper layers
were important for carbon and nitrogen
storage, which leads to improved soil and
environmental quality.
The literature holds considerable evidence
that intensive tillage decreases soil
carbon and supports the increased adoption
of new and improved forms of conservation
tillage or direct seeding to preserve or
increase SOM (Reicosky et al., 1995; Paul
et al., 1997; Lal et al., 1998). Based on the
soil carbon losses with intensive agriculture,
reversing the decreasing soil carbon
trend with less tillage intensity should be
beneficial to agriculture and the global population
by gaining better control of the
global carbon balance (Houghton et al.,
1983; Schlesinger, 1985). The environmental
and economic benefits of conservation
tillage and direct seeding demand their consideration
in the development of improved
management practices for sustainable production.
However, the benefits of no-tillage
for soil organic carbon sequestration may be
soil- or site-specific, and the improvement
of soil organic carbon may be inconsistent
on fine-textured and poorly drained soils
(Wander et al., 1998). Six et al. (2004) indicated
a strong time dependency in the
greenhouse gas (GHG) mitigation potential
of no-tillage agriculture, demonstrating that
greenhouse gas mitigation by adoption of
no-tillage is much more variable and complex
than previously considered.
Policy of Carbon Credits
The increase in greenhouse gas concentrations
in the atmosphere is a global problem
that requires a global solution (Kimble
et al., 2002; Lal, 2002). Concern about negative
effects of climate warming resulting
from increased levels of greenhouse gases
in the atmosphere has led nations to establish
international goals and policies for
reductions of these emissions. Initial targets
for reductions are stated in the Kyoto
Protocol of the United Nations Framework
Convention on Climate Change, which
allows trading credits that represent verified
emission reductions and removal of
greenhouse gases from the atmospheres
(United Nations Framework Convention on
Climate Change Secretariat, 1997).
Emissions trading may make it possible
to achieve reductions in net greenhouse gas
emissions for far less cost than without
trading (Dudek et al., 1997). Storing carbon
in soils using conservation agriculture
techniques can help offset greenhouse gas
emissions while providing numerous environmental
benefits, such as increasing site
productivity, increasing water infiltration
and maintaining soil flora and fauna diversity
(Lal et al., 1998; Lal, 2002). Storing carbon
in forests may also provide environmental
benefits resulting from increased numbers
of mature trees contributing to carbon
sequestration (Row et al., 1996). While carbon
is a key player for agriculture in solving
the problem of global warming, a critical
caveat is that other greenhouse gases
change with changes in land use, including
CH4 and N2O. We must look at the net
global warming potential, not only for carbon
in future trades but global warming
potential credits, rather than carbon credits
alone.
As interest in soil carbon sequestration
grows and international carbon trading
markets are developed, it is important that
appropriate policies be developed that will
prevent the exploitation of soil organic
carbon and at the same time replace the lost
carbon and establish its value (Walsh,
2002). Policies are needed that will encourage
the sequestration of carbon for all environmental
benefits that will evolve (Kimble
et al., 2002). Making carbon a commodity
necessitates determining its market value
and doing so with rational criteria.
Both farmers and society will benefit
from sequestering carbon. Enhanced soil
quality benefits farmers, but farmers and
society in general benefit from erosion control,
reduced siltation of reservoirs and
waterways, improved air and water quality
and biodegradation of pollutants and chemicals.
Farmers need to be compensated for
Reduced Environmental Emissions 265
the societal benefits of carbon sequestration
and the mechanisms that develop will
allow for carbon trading and maintaining
property rights. One important criterion in
developing the system is the measurement
and verification of the carbon options for
sequestration that must be developed and
the importance of making policymakers
aware of these procedures and the technical
difficulties. The use of international carbon
credit market mechanisms is intended to
help meet the challenge of climate change
and future carbon constraints, which enable
sustainable development and at the lowest
social cost.
Carbon credit accounting systems must
be transparent, consistent, comparable,
complete, accurate and verifiable (IPCC,
2000). Other attributes for a successful system
include global participation and market
liquidity, linking of different trading
schemes, low transaction costs and rewards
for early actions to voluntarily reduce emissions
before regulatory mandates are put
in place. Characterizing the relationships
between soil carbon and water quality, air
quality and all the other environmental
benefits should be an easy sell to get social
acceptance of this type of agriculture. The
largest impediment is the educational processes
directed at the policymakers and
food-consuming public, which require further
enhancement.
A growing number of organizations
around the world are implementing voluntary
projects that are climate-beneficial as a
means to improve efficiency and reduce
operating costs and risk. Businesses and
institutions throughout the world are realizing
that the benefits of good environmental
management far outweigh the cost, both
now and in the future, of good corporate
management, which includes strategies to
reduce greenhouse gas emissions, risk
exposure and costs and to enhance overall
competitive operations. Multinational organizations
are participating in carbon energy
credit trading markets in order to avoid
future compliance costs and to protect their
global franchise in the face of increasing
concern over global warming (Walsh, 2002).
In the evolution towards a global economy
and as concerns over global environmental
impacts increase, CO2 emission management
will become a factor in the planning and
operations of industrial and government
entities all over the world, creating challenges
and opportunities for those who are
able to recognize and capitalize on them.
The global ecosystem services provided
by farmers and other landowners
could provide a source of carbon-emission
credits to be sold to carbon emitters and
hence provide an additional source of
income for farmers, particularly no-tillage
farmers. Trade in carbon credits has the
potential to make conservation agriculture
more profitable and enhance the environment
at the same time. The potential for
carbon credits has attracted considerable
attention of farmers and likely buyers of the
carbon credits. However, it is difficult to
stay fully informed about developing
carbon credits because of their technical
complexity and the pace of development on
this subject. Rules for trading in carbon
credits are not yet agreed upon, but international
dialogue is under way to develop a
workable system and rules for trading. The
number of organizations working on developing
a carbon trading system suggests that
some type of international mechanism will
evolve and that carbon credit trading will
become a reality.
Information is rapidly becoming available
on publicly traded carbon credits;
however, little information is available on
privately traded contracts. A great deal of
uncertainty exists at this time as to which
companies will emerge as reliable sources
of high-quality information and entities that
can handle trading in a fair and reliable
manner. Potential suppliers and buyers of
carbon credits are urged to proceed with
caution because many of the issues central to
carbon credit markets and trade are yet to be
clarified. We must convince policymakers,
environmentalists and industrialists that
soil carbon sequestration is an additional
important benefit of adopting improved
and recommended conservation agricultural
production systems. This option
stands on its own, regardless of the threat of
global climate change from fossil fuels.
266 D.C. Reicosky and K.E. Saxton
Conservation agricultural practices
(especially no-tillage) can help to mitigate
global warming by reducing carbon emissions
from agricultural land and by sequestering
carbon in the soil through regulatory,
market incentive and voluntary or educational
means (Lal, 2002). Public policy can
encourage adoption of these practices.
For the present, there is a degree of uncertainty
for investors and potential investors
in forest-related carbon sinks over the specific
rules that will apply to implementation
of the sinks provisions of the Kyoto
Protocol. Investors and potential investors
in carbon sinks need to be aware that there
is uncertainty at the international level.
Administration and transaction costs could
play a key role in determining the success
of any carbon credit trading system. Costs
in these areas are expected to be minimized
through improved techniques and services
for measuring and reporting sequestered
carbon, private-sector consultants, economies
of scale and the emergence of market
mechanisms and strategies such as carbon
pooling or aggregating. There are risks
involved in selling carbon credits in advance
of any formalized international trading system
and those participating in early trading
need to clarify responsibilities and obligations.
However, care should be taken in the
design of these policies to ensure their
success, to avoid unintended adverse economic
and environmental consequences
and to provide maximum social benefit.
Summary of Reduced Environmental
Emissions and Carbon Sequestration
While we learn more about soil carbon
emissions, soil carbon storage and their
central roles in environmental benefits, we
must understand the secondary environmental
benefits of no-tillage and what they
mean to sustainable production agriculture.
Understanding these environmental benefits
directly related to soil carbon and getting the
conservation practices implemented on the
land will hasten the development of harmony
between humans and nature while
increasing production of food, fibre and
biofuels.
Reducing soil carbon emissions and
increasing soil carbon storage can increase
infiltration, increase fertility, decrease
wind and water erosion, minimize compaction,
enhance water quality, impede
pesticide movement and enhance environmental
quality. Increased levels of greenhouse
gases in the atmosphere require all
nations to establish international and
national goals and policies for reductions.
Accepting the challenges of maintaining
food security by incorporating carbon storage
in conservation planning demonstrates
concern for our global resources and our
willingness to work in harmony with
nature. This concern presents a positive
role for no-tillage, which will have a major
impact on global sustainability and our
future quality of life.
Reduced Environmental Emissions 267
18 Some Economic Comparisons
C. John Baker
The long-term economics of no-tillage will
be determined more by maximizing crop
performance and net cash returns than by
minimizing the inputs costs.
In this chapter we look at some economic
comparisons of tillage versus no-tillage.
But, no matter how the comparisons are
analysed, in the end, crop yield will affect
the results at least as much as input costs.
Comparisons between different levels
of no-tillage are also important. For example,
a relatively inexpensive no-tillage drill
costing half as much as a more advanced
alternative will only need to cause a 4–5%
reduction in crop yield to become a bad
investment.
But the most common comparison is
between no-tillage and tillage. Opinions
abound about whether it is cheaper to use
no-tillage or tillage. Comparisons are often
misleading for the following reasons:
1. Farmers who consider changing from
tillage to no-tillage often compare the cost
of engaging a no-tillage contractor (custom
driller) with the cost of undertaking their
own tillage. Many only include direct costs
(such as fuel) as the cost of undertaking tillage
since they already own the equipment,
which they consider has already been paid
for. The real issue is not apparent until
these farmers have to replace their worn-out
tillage equipment. None the less, we attempt
to analyse this situation by comparing the
cost of used tillage equipment with used
no-tillage equipment.
2. Understandably, even if farmers are
determined to make a switch to no-tillage,
they will often keep their tillage equipment
for a few years as a form of insurance – ‘in
case no-tillage does not work out’ – while
also paying for a no-tillage contractor. Thus,
for a period, they are paying twice, but not
by as much as they might imagine, as
shown later by the analyses.
3. Many comparisons penalize no-tillage
by imposing expected reductions in crop
yields and/or increases in seeding and/or
fertilizer rates for the first few years. This no
longer applies when using modern no-tillage
equipment and methodologies. Recent experience
has repeatedly shown that using
advanced no-tillage machinery and systems
will produce crop yields at least comparable
to tillage in year 1, and probably significantly
better with time. Seeding rates of some crops
and pastures have actually been reduced, not
increased – some by up to 50%. On the other
hand, if lower technology no-tillage systems
and equipment are used, temporary yield
reductions may well be applicable.
4. Economic comparisons should, but seldom
do, factor in no-tillage reductions in
labour, tractor numbers, tractor hours, fuel
© FAO and CAB International 2007. No-tillage Seeding and Conservation
268 Agriculture, 2nd edn. (eds C.J. Baker and K.E. Saxton)
use and depreciation. One US farmer, for
example, using modern no-tillage methods,
recently reported that he now uses
more fuel to harvest his crops than to grow
them – an unheard-of scenario using conventional
tillage (D. Wolf, 2005, personal
communication).
5. Tractors often clock only one-quarter of
the annual hours using no-tillage compared
with tillage and thus last considerably
longer. Therefore, the annual depreciation,
interest and insurance costs can be reduced
and machinery replacement intervals
lengthened.
6. Some farmers already have a permanent
labour force and no alternative function
for that labour when the demand at
seeding is reduced; thus there is seemingly
little to be gained by adopting no-tillage. On
the other hand, enterprising farmers have
used the freed-up time to increase the area
cropped each year. The economics of this
are hard to factor into any analysis.
7. The amount of capital recovered from
the sale of second-hand tillage equipment
will diminish as no-tillage increases in popularity.
The market for second-hand tillage
equipment will shrink and this has certainly
been a factor for some farmers when
making the change.
So how do the figures stack up on both
sides of tillage versus no-tillage? We provide
answers to this question from two perspectives.
The first was to examine four possible
scenarios of ownership (C.J. Baker, 2000,
unpublished data). We use the costs of
equipment in New Zealand because that
country has some of the more expensive
and capable no-tillage options available, as
well as cheaper alternatives. The second
analysis was to review the results of charges
made by a contractor in England to a client
over two seasons. The first season (2002/03)
was for tillage and minimum tillage. The
second season (2003/04) was for no-tillage
(J. Alexander, 2004, personal communication).
In both analyses we assume that crop
yields are the same for both tillage and notillage.
Such an assumption is only realistic
if advanced (and usually more expensive)
no-tillage equipment is used. If less advanced
(cheaper) no-tillage equipment is used, it is
likely that crop yields will be depressed
below tillage, which will add an effective
additional cost to the no-tillage. The comparisons
quoted below may therefore require
adjustment for less advanced equipment.
Obviously the actual figures will require
adjustment for other countries and years.
But readers are encouraged to change the
input data to those applying locally and
recalculate the figures. In most cases the
relative values will remain approximately
the same, regardless of how the actual
figures change over time and location.
New Zealand Comparisons
● Scenario A: Economics of using a tillage
contractor or a no-tillage contractor.
● Scenario B: Economics of purchasing
new tillage or new no-tillage equipment.
● Scenario C: Economics of retaining used
tillage equipment or purchasing either
new or used no-tillage equipment.
● Scenario D: Economics of retaining
used tillage equipment or engaging a
no-tillage contractor.
Assumptions
1. Farmed area 300 hectares – 150 hectares
cropped twice annually. (The cropped
area could increase substantially with
no-tillage but this is not included.)
2. With no-tillage, glyphosate, slug bait
and chlorpyrifos are used in spring for
weed and pest control.
3. For tillage, glyphosate is applied prior
to spring ploughing (at a lighter rate than for
no-tillage) but is omitted for autumn sowing.
4. All values are shown in 2004 New
Zealand dollars.
Scenario A: Economics of using a tillage
contractor or a no-tillage contractor
Establishing 150 hectares of spring wheat
(Table 18.1), followed by 150 hectares of
autumn forage crop (Table 18.2). Table 18.3
summarizes the pre-tax costs.
Economic Comparisons 269
CONCLUSIONS
1. On a contractor basis, costs (and
therefore gross margins) for the year favour
no-tillage by $16,500 or $55/ha.
2. Even if glyphosate is omitted from tillage
in the spring (at $55/ha), the comparison
still favours no-tillage by $8250 per year or
$27.50/ha for the whole year.
3. No allowance has been made in this
analysis for the benefits of establishing
autumn crops or pasture using advanced
no-tillage methods immediately after
harvest, nor for the additional spring utilization
of land that comes from no-tillage.
These factors alone can be valued at an
additional $440/ha in favour of no-tillage
(W.R. Ritchie, 2003, unpublished data).
NOTES
1. When sowing brassicas, peas or other
broadleaved crops in spring, the chlorpyrifos
cost for no-tillage can be reduced to $8/ha,
which reduces the per-hectare cost of
no-tillage in spring to $213/ha (overall cost
$140/ha), increasing the overall difference
between the two to $87/ha in favour of
advanced no-tillage.
2. Contract tillage varies by district from
$250/ha to $500/ha. The conservative lower
figure was used.
3. Contract no-tillage with advanced
equipment varies from $100/ha to $150/ha,
depending on contour, size of field, etc. The
conservative lower figure was used.
4. If using cheaper no-tillage equipment,
drilling costs will be reduced, but crop
yields are likely to be reduced by more than
the saving in costs.
5. Herbicides and pesticides are often
unnecessary in autumn with no-tillage.
Some or all may be necessary in other
situations, in which case their cost at
reduced application rates should be added
to no-tillage.
6. Autumn tillage in New Zealand (NZ)
usually involves minimum tillage.
Scenario B: Economics of purchasing new
tillage or new no-tillage equipment
Establishing 150 hectares of spring wheat followed
by 150 hectares of autumn forage crop.
The capital costs associated with purchasing
all new equipment are shown in Table 18.4.
The annual pre-tax operating costs of the two
systems are shown in Table 18.5.
270 C.J. Baker
Item Tillage No-tillage
Glyphosate (including
application)
$55/haa $65/ha
Chlorpyrifos (applied
with glyphosate)
$40/hab
Slug bait (applied
with drill)
$40/ha
Contractor $250/ha $100/ha
Seed and fertilizer Same Same
Total $305/ha $245/ha
Crop yield Same Same
× 150 hectares $45,750 $36,750
aGlyphosate is applied at a lower rate for tillage.
bThe chlorpyrifos cost would reduce to $8/ha when
there was lighter pest pressure.
Table 18.1. Spring cropping using contractors.
Item Tillage No-tillage
Glyphosate
Chlorpyrifos
Slug bait
Contractor $150/ha $100/ha
Seed and fertilizer Same Same
Total $150/ha $100/ha
Crop yield Same Same
× 150 hectares $22,500 $15,000
Table 18.2. Autumn cropping using contractors.
Tillage No-tillage
Costs $68,250 $51,750
Costs/ha $227/ha $172/ha
Difference (in favour
of no-tillage)
$16,500
($55/ha)
Table 18.3. Summary of total annual pre-tax costs.
CONCLUSIONS
1. The capital cost of advanced no-tillage
equipment was very similar to new tillage
equipment.
2. With new equipment, annual savings
in operating costs of approximately $18,000
per year ($61/ha) will be achieved by purchasing
advanced no-tillage equipment
rather than tillage equipment.
NOTES
1. Depreciation was calculated on a
straight-line basis as:
Tillage tractors: Annual depreciation =
new price minus trade-in price (50%
of new price) divided by service life
(10 years).
No-tillage tractor: Annual depreciation =
new price minus trade-in price (50%
Economic Comparisons 271
Item Tillage No-tillage
1 × 170 hp tractor $170,000
1 × 120 hp tractor $120,000
1 × 80 hp tractor $80,000
Sprayer $6,000 $6,000
Plough (5 furrow) $28,000
Power harrow (3 m) $23,000
Roller $6,000
Leveller $3,000
Drill $34,000 $120,000
Total capital cost $300,000 $296,000
Difference Negligible
Table 18.4. Pre-tax capital costs of purchased new equipment.
Item Tillage No-tillage
Depreciation1
(tractors) $10,000 $4,250
(other equipment) $2,500 $3,150
Interest2 (9%) on average investment $20,250 $19,980
Maintenance3 (tractors @ 5%/year) $10,000 $8,500
Maintenance3 (soil-engaging equipment @ 7%/year) $6,580 $8,400
Maintenance3 (non-soil-engaging equipment @ 3%/year) $180 $180
Fuel
(50 l/ha spring tillage) @ 65c/l $4,875
(25 l/ha autumn tillage) @ 65c/l $2,438
(15 l/ha spring and autumn no-tillage) @ 65c/l $2,925
Labour
(4 h/ha spring tillage) @ $15/h $9,000
(2 h/ha autumn tillage) @ $15/h $4,500
(1 h/ha spring and autumn no-tillage) @ $15/h $4,500
Total annual operating cost $70,323 $51,885
Cost per hectare $234 $172
Difference (in favour of no-tillage) $18,438
(or $61/ha)
1,2,3 See ‘Notes’ on pp. 271–272.
Table 18.5. Annual pre-tax operating costs of new equipment.
of new price) divided by service life
(20 years).
All other equipment: Annual depreciation
= new price minus trade-in price
(50% of new price) divided by service
life (20 years).
2. Interest was calculated on the average
investment (new price plus trade-in price
divided by 2) × 0.09.
3. Maintenance was from published data
(Bainer et al., 1955).
4. Actual total cost of labour will probably
be closer to $20/hour if allowance is made
for downtime, travel, maintenance, etc.
Scenario C: Economics of retaining used
tillage equipment or purchasing either new
or used no-tillage equipment
Establishing 150 hectares of spring wheat
followed by 150 hectares of autumn forage
crop. The capital costs associated
with purchasing new or used no-tillage
equipment, compared with retaining ownership
of used tillage equipment, are
shown in Table 18.6. The annual pre-tax
operating costs of new or used no-tillage
equipment versus used tillage equipment
are shown in Table 18.7.
CONCLUSION. Capital costs are virtually
halved by owning second-hand equipment
(tillage or no-tillage) compared
with new equipment. Some $95,000–
$97,500 in capital cost is saved by purchasing
second-hand tillage or no-tillage
equipment.
NOTE
1. The value of used equipment was
assumed to be two-thirds of its new value
and the equipment is halfway through its
service life. The trade in value remains at
50% of the new value at the end of its
service life.
272 C.J. Baker
Item
Tillage
(used)1
No-tillage
(new)
No-tillage
(used)1
1 × 170 hp tractor $170,000 $114,000
1 × 120 hp tractor (3300 h) $80,000
1 × 80 hp tractor (3300 h) $54,000
Sprayer $4,500 $6,000 $4,500
Plough (5 furrow, used) $19,000
Power harrow (3 m, used) $15,500
Roller (used) $4,500
Leveller (used) $4,500
Conventional drill (used) $23,000
No-tillage drill $120,000 $80,000
Total capital cost $205,000 $296,000 $198,500
Difference (in favour of used
equipment – see Scenario B above)
$95,000 $97,500
Table 18.6. Pre-tax capital costs of new no-tillage and used tillage and no-tillage
equipment.
CONCLUSIONS
1. Annual costs of owning and operating
used tillage equipment ($59,228/year) were
approximately $11,000 lower than for
new tillage equipment ($70,323/year –
Scenario B).
2. The annual costs of owning and operating
used tillage equipment ($59,228/year)
were approximately $7000 (or $24/ha)
greater than owning and operating new
advanced no-tillage equipment ($51,885/
year) and approximately $14,000 (or
$46/ha) greater than used advanced notillage
equipment.
NOTES
1. Depreciation was calculated on a
straight-line basis as follows:
Tillage tractors: Annual depreciation =
used price minus trade-in price
(50% of new price) divided by
remaining service life (5 years).
No-tillage tractor: Annual depreciation
= new or used price minus
trade-in price (50% of new price)
divided by remaining service life (20
years for new or 10 years for used).
All other equipment: Annual depreciation
= new or used price minus
trade-in price (50% of new price)
divided by remaining service life
(20 years for new or 10 years for
used).
2. Interest was calculated on the average
investment (used or new price plus trade-in
price divided by 2) × 0.09.
3. Maintenance was from published data
(Bainer et al., 1955).
4. The maintenance costs shown for used
equipment are conservative because maintenance
could be expected to increase with
age of machines.
Economic Comparisons 273
Item Tillage (used) No-tillage (new) No-tillage (used)
Depreciation1 (tractors) $6,800 $4,250 $2,900
Depreciation1 (other equipment) $2,100 $3,150 $2,150
Interest2 @ 9% (tractors and equipment) $15,975 $19,980 $15,592
Maintenance3 (tractors @ 5% new
price/year)
$10,000 $8,500 $8,500
Maintenance3 (soil-engaging equipment
@ 7% new price/year)
$3,360 $8,400 $8,400
Maintenance3 (non-soil-engaging
equipment @ 3% new price/year)
$180 $180 $180
Fuel
(50 l/ha spring tillage) @ 65c/l $4,875
(25 l/ha autumn tillage) @ 65c/l $2,438
(15 l/ha spring and autumn no-tillage)
@ 65c/l
$2,925 $2,925
Labour
(4 h/ha spring tillage) @ $15/h $9,000
(2 h/ha autumn tillage) @ $15/h $4,500
(1 h/ha spring and autumn no-tillage)
@ $15/h
$4,500 $4,500
Total annual operating cost $59,228 $51,885 $45,147
Cost per hectare $197 $173 $150
Difference (in favour of no-tillage) $7,343
(or $24/ha)
$14,081
(or $46/ha)
1,2,3 See ‘Notes’ on p. 273.
Table 18.7. Annual pre-tax operating costs of new and used no-tillage and used tillage equipment.
Scenario D: Economics of retaining used
tillage equipment or engaging a no-tillage
contractor
Establishing 150 hectares of spring wheat followed
by 150 hectares of autumn forage crop.
The annual pre-tax costs of operating used
tillage equipment versus hiring a no-tillage
contractor are shown in Table 18.8.
CONCLUSION
1. Ownership of used tillage equipment was
more expensive (by approximately $15,000
per year or $52/ha) than engaging a contractor
with advanced no-tillage equipment.
Summary and conclusions
The A–D scenarios outlined above are
summarized in Table 18.9.
General conclusions
1. It made little difference whether such
comparisons were made between new or
used equipment, hiring contractors, or
combinations of these options. No-tillage
was less expensive than tillage for all
situations.
2. For 150 hectares cropped twice per year,
it was cheaper to use advanced no-tillage
equipment in any form than to use any form
of tillage ($7000–$18,000/year, or $24–$61/
hectare).
3. The smallest difference was ownership
of used tillage versus ownership of new
no-tillage equipment ($24/ha).
4. The largest difference was ownership
of new tillage versus ownership of new
no-tillage equipment ($61/ha).
5. All other comparisons result in an
approximate $50/ha saving using no-tillage.
6. Hiring a no-tillage contractor with
advanced equipment is most often accompanied
by a high level of specialist expertise.
7. The only valid economic argument for
not adopting advanced no-tillage is if a
farmer does not have access to an advanced
no-tillage drill. Substandard crop yields
will be likely, if not a regular occurrence,
with less advanced no-tillage equipment.
Tillage is more forgiving of substandard
equipment.
8. If a farmer chooses to continue
ownership of the used tillage equipment
while hiring a no-tillage contractor with
advanced equipment on a trial basis (a
sensible practice), the costs of depreciation
and interest on the tillage equipment
will remain although it is not being used
($80/hectare, Scenario C). Since the use of
274 C.J. Baker
Item Tillage No-tillage
Annual operating
costs of used tillage
equipment (from
Scenario C)
$59,228
Glyphosate in spring
(from Scenario A)
$8,250
Annual cost of
contractor including
glyphosate and
pesticides (from
Scenario A)
$51,750
Totals $67,478 $51,750
Cost per hectare $225 $172
Difference (in favour
of no-tillage)
$15,728
($52/ha)
Table 18.8. Costs of used tillage equipment
versus hiring a no-tillage contractor.
Tillage
($/year)
Tillage
($/ha)
No-tillage
($/year)
No-tillage
($/ha)
Differences
Scenario $/year $/ha
Scenario A (contractors) 68,250 227 51,750 172 16,500 55
Scenario B (own new equipment) 70,323 234 51,885 173 18,438 61
Scenario C (own used equipment) 59,228 197 45,145–51,885 150–173 7,343–14,081 24–47
Scenario D (own used equipment
versus contractor)
67,478 225 51,750 172 15,728 53
Table 18.9. Summary of Scenarios A–D.
a no-tillage contractor is less than a tillage
option ($53/ha, Scenario D), the net
cost of trying out advanced no-tillage for a
year will be about $27/ha ($80–$53),
which is a modest price to pay with the
prospect of saving $24–61/ha/year for
every year thereafter with the adoption of
no-tillage.
European Comparisons
In these comparisons, an English tillage
contractor provided the following figures
for a client who cropped 404 hectares (1000
acres) per year. The tillage and minimumtillage
figures were actual charges made
to the farmer in previous years. The
advanced no-tillage figures were quotations
for 2004.
Two scenarios are compared: ploughbased
tillage versus no-tillage, and minimum
tillage versus no-tillage. The tillage and
minimum-tillage programmes are outlined in
Tables 18.10 and 18.11 and are considered
typical for many English properties.
The no-tillage quote was for an
advanced and more expensive no-tillage
drill (which would assure crop production
with at least equal yield to the tillage systems),
as reflected in the higher perhectare
charge rate. As with the New
Zealand comparison, substituting a less
advanced no-tillage drill for the advanced
no-tillage drill might have had the potential
to reduce the costs of no-tillage but
it also had the potential to reduce the
no-tillage crop yield.
Scenario (A) Comparison of no-tillage with
full plough-based tillage
Establishing cereal grain on a 404 hectare
(1000 acre) farm using a plough-based
tillage system, compared with advanced
no-tillage (contractor charges). Comparative
costs are shown in Table 18.10.
Economic Comparisons 275
Cost/ha Area Total
Tillage machines
Subsoiler, with packer roller £31.75 404 £12,827.00
Ploughing £36.00 404 £14,544.00
‘Cultipress’ £14.20 404 £5,736.80
Rolling £10.75 404 £4,343.00
Power harrow £25.60 200 £5,120.00
Fertilizing £7.50 404 £3,030.00
Combination conventional drill £29.75 304 £9,044.00
Cultivator-drill £30.00 100 £3,000.00
Spraying £7.00 404 £2,828.00
Total £60,472.80
No-tillage machines
Advanced no-tillage drill £55.00 404 £22,220.00
Spraying £7.00 404 £2,828.00
Total £25,048.00
Difference £35,424.80
Difference per hectare £87.68/ha
Table 18.10. Comparison of tillage and no-tillage costs in England.
Scenario (B) Comparison of no-tillage with
minimum tillage
Establishing cereal grain on a 404 hectare
(1000 acre) farm using a minimum-tillage
system, compared with advanced no-tillage
(contractor charges). Comparative costs
are shown in Table 18.11.
Conclusions
1. On a contractor basis, minimum tillage
was cheaper than tillage by £29/ha.
2. On a contractor basis, advanced notillage
was cheaper than plough-based
tillage by £87/ha.
3. On a contractor basis, advanced notillage
was cheaper than minimum tillage
by £58/ha.
4. These comparisons may not have been
valid if less advanced no-tillage machines
had been used.
5. Comparisons between tillage, minimum
tillage and no-tillage are machine-dependent,
since no-tillage drill designs have the potential
to influence crop yields markedly.
Summary of Some Economic
Comparisons
1. The most common economic comparison
is between no-tillage and tillage but such
comparisons are often misleading for any
one of a number of reasons and assumptions.
2. Several possible scenarios provide economic
examples of tillage versus no-tillage,
but the items and figures will require
changing for other countries and years.
3. Machine costs involved with changing
from a tillage to a no-tillage system are a
major consideration.
4. Maintaining ownership of tillage machines
for a period after beginning no-tillage
adds some costs to the transition but may be
a comforting and affordable choice for many
farmers.
5. Economics of using a tillage contractor
or a no-tillage contractor favours using a
no-tillage contractor.
6. Economics of purchasing new tillage or
new advanced no-tillage equipment showed
similar capital costs in either case but significantly
lower operating costs for no-tillage.
7. Economics of retaining used tillage
equipment or purchasing either new or used
no-tillage equipment showed that capital
costs are virtually halved by owning secondhand
equipment (tillage or no-tillage),
compared with new equipment, but again
operating costs are in favour of no-tillage.
8. Economics of retaining used tillage
equipment or engaging a no-tillage contractor
showed that ownership of used tillage equipment
was more expensive than hiring a contractor
with advanced no-tillage equipment.
9. It made little difference whether comparisons
were made between new or used
equipment, hiring contractors, or combinations
of these options. No-tillage was less
expensive than tillage for all situations.
10. Hiring a no-tillage contractor with advanced
equipment is most often accompanied
with a high level of specialist expertise.
11. A US farmer who recently converted from
tillage to no-tillage reports a ‘win–win’ situation
with advanced no-tillage equipment. He
has not only recorded his best crop yields
ever with no-tillage, but he now also uses less
fuel to grow his crops than to harvest them.
276 C.J. Baker
Cost/ha Area Total
Minimum-till machines
Subsoiler, with
packer roller
£31.75 202 £6,413.50
Tillage train £35.00 404 £14,140.00
‘Cultipress’ £14.20 404 £5,736.80
Rolling £10.75 404 £4,343.00
Fertilizing £7.50 404 £3,030.00
Cultivator-drill £30.00 404 £12,120.00
Spraying £7.00 404 £2,828.00
Total £48,611.30
No-tillage machines
Advanced
no-tillage drill
£55.00 404 £22,220.00
Spraying £7.00 404 £2,828.00
Total £25,048.00
Difference £23,563.30
Difference per
hectare
£58.32/ha
Table 18.11. Comparison of minimum tillage and
no-tillage costs in England.
19 Procedures for Development and
Technology Transfer
C. John Baker
Measuring the mechanical performance of
no-tillage machines is far less important than
measuring their biological performance.
One of the distinguishing aspects of experiments
conducted with agricultural tillage
machines is that there are very few common
experimental techniques and standardized
instruments that can be universally applied.
The designs and functions of most agricultural
machines are quite diverse; thus the
techniques used to evaluate them are tailormade
for specific purposes and to answer
specific questions.
This situation contrasts with experiments
with plants, for example, in which the
most common procedure is to grow plants in
pots or plots of soil, each with a designated
treatment. Since all plants perform essentially
the same functions of utilizing the
sun’s energy to convert nutrients from the
soil, atmosphere and water into biomass,
there is a high degree of commonality of plant
experiments.
In the study of no-tillage drills, planters
and openers, design scientists have
sought knowledge not only about resulting
plant growth, using well-established experimental
procedures, but also about their
mechanical performance and, perhaps most
importantly, about the interactions between
infinite design variations of the machine
components, the soil, surface residues, pests
and the plants.
Described here are some of the experimental
procedures and techniques used by
the authors and their colleagues to gain knowledge
about the functions and performance
of no-tillage components and subsequently
to develop new no-tillage technologies,
designs and practices. Many of the techniques
developed are specific to no-tillage
but should be useful to others pursuing
similar investigations. Some were unique
experiments, while others followed wellestablished
common procedures.
This is not an attempt to provide a
comprehensive review of all techniques
used by scientists in this field, although
the results of much relevant work by a
wide range of scientists are reported elsewhere
in this book. The technique descriptions
and instrumentation given here
are restricted to those used or devised by
the authors. We explain how many of the
experiments were conducted in some
detail because they were designed to address
a variety of questions about how plants
and soil interact with no-tillage machines,
and because there were no known methodologies
for those purposes available at the
time.
© FAO and CAB International 2007. No-tillage Seeding in Conservation
Agriculture, 2nd edn. (eds C.J. Baker and K.E. Saxton) 277
The techniques and procedures described
examined the following subjects:
1. Plant responses to no-tillage openers in
controlled conditions.
2. The micro-environment within and
surrounding no-tillage seed slots.
3. Soil compaction and disturbance by
no-tillage openers.
4. Locating seeds in the soil.
5. Seed travel within no-tillage openers.
6. Drag on a disc opener.
7. Accelerated wear tests of no-tillage
openers.
8. The effects of fertilizer banding.
9. Prototype drills and management
strategies.
Plant Responses to No-tillage
Openers in Controlled Conditions
It is often assumed that most seeds will germinate
and grow satisfactorily if sown into
moist soil followed by favourable climatic
conditions. Unfortunately, under no-tillage
this assumption is not always correct. Early
experience with no-tillage had suggested that,
as the soil and climatic conditions became
less favourable, seed, seedling and plant performance
often suffered more than where
seeds were sown into tilled seedbeds.
Thus, it became important to develop a
fundamental procedure to evaluate the biological
performance of different no-tillage
openers under controlled conditions. The
aim was to create a facility where scientists
could put stress on the no-tillage system by
superimposing unfavourable soil moisture
conditions followed by unfavourable climatic
conditions without the risk of intervention
by unpredictable weather.
Sowing seeds in the field was considered
too impractical and imprecise to control the
soil moisture and climate. Conventional
‘rainout’ shelters, which involve large
movable transparent canopies covering several
plots of soil, were expensive and would
have limited the experiments to one site.
This contrasted with tillage experiments,
where the soil beneath a ‘rainout’ shelter
can be re-tilled several times to repeat several
experiments on the same site.
The scientists also did not have the
convenience of being able to place seeds in
disturbed soils that had been prepared in
pots or trays so that they could later be
transported into glasshouses or other artificially
controlled climate laboratories. For
no-tillage experiments, the soils had to have
been truly undisturbed for at least 12 months,
and preferably longer, and to remain this
way throughout the experiments.
A new technique was developed to
transport untilled soil in bins to an indoor
climatically controlled facility. This involved
removing large 2.0 m × 0.7 m × 0.2 m blocks
of soil weighing approximately 0.5 t from
the field in an undisturbed state, controlling
pre-drilling soil moisture content, drilling
with openers arranged to duplicate their
performance on a field drill or planter and
then controlling the post-drilling climate and
soil moisture content for the duration of the
experiment (Baker, 1969a, 1976a, b).
Rectangular steel bins were constructed
with both ends open. The front end of each
bin was able to be attached to the rear of a
stirrup-shaped soil cutter, which was itself
attached to and pulled through the soil by a
tractor (Fig. 19.1). The horizontal blade of
the cutter was hollow, with exit ports drilled
along its rearmost edge. Water was pumped
into the hollow blade during extraction of
the 0.5 t soil blocks to create a thin slurry on
the underside of each soil block and thus
temporarily lubricate it as it slid along each
of the 2 metre bins. The base of each bin was
lined with a veneer of stainless steel to assist
this process.
In practice, it was found that 2 m was
about the maximum slice length that a
200 mm deep undisturbed soil slab could
be expected to slide without becoming compressed
and perhaps buckled. Increasing
the depth beyond 200 mm may have permitted
longer blocks to be extracted, but such
bins would have been difficult to handle
because of their added weight and length.
Although a 200 mm soil depth could
not be expected to sustain plant growth for
long periods before roots reached the stainless
steel bases, all of the studies that utilized
278 C.J. Baker
these bins concentrated on the germination
and seedling emergence phases of crop production,
since these were considered to be
the most critical phases obstructing reliable
no-tillage. It was also considered that machine
influences on plant growth were likely to be
greatest at the germination and emergence
phases and thereafter would be of less influence
than other factors, such as weather, soil
and management effects.
The soil remained in its bin throughout
each experiment. Bins were transported from
the field to the laboratory using heavy lifting
equipment on a tractor (Fig. 19.2). The
moisture content of the soil in each bin was
manipulated either by covering each bin
with clear plastic and leaving it to air-dry or
by irrigating it from above by sprinkler or
from below by placing the perforated bins
in shallow troughs containing a predetermined
quantity of water.
Two processes were used to drill these
undisturbed blocks of soil with a variety of
no-tillage openers. Where measurements of
the drilling process itself were to be made or
multiple openers were to be tested in each
bin, five bins were placed end to end on the
raised bed of a ‘tillage bin’ arrangement,
which also had a tool carrier on a moving
gantry that straddled the line of bins and
could be moved forwards or backwards at
infinitely variable speeds from 0 to 8 km/h
(0 to 5 mph) (Fig. 19.3).
Where drilling took place indoors, the
openers on test were usually arranged at
150 mm row spacing with three rows to a
bin. This resulted in 200 mm of clearance
between the outside rows and the edges of
the bins. The slightly larger distance in this
zone was to avoid soil disturbance at the bin
edges. All openers were mounted on parallel
drag arms attached to a subframe. The vertical
angle was variable to alter the opener pitch
for any geometrical arrangement. Downforce
was applied by adding weights to individual
openers and draught forces were measured
by a load cell mounted within the
drag arm attachment subframe.
Mounting openers on parallel arms
and applying downforce by application of
weights were not a true duplication of common
field practice. Weights ensured that
the downforce applied to any one opener
remained constant regardless of its position
in the vertical plane. This seldom happens
in practice. But the objective was to remove
most ancillary functional differences between
openers and their modes of operation to
Development and Technology Transfer 279
Fig. 19.1. A stirrup-shaped soil cutter with bin attached for extracting undisturbed soil blocks
(from Baker, 1969a).
evaluate differences associated with their
actions in the soil and the shape of the slots
they created.
Individual seeds were metered by amodified
vacuumseeder designed by Copp (1961).
As drilling was usually conducted at slow
speeds, a visual count was made of the
seeds entering the soil by observing them as
they passed down a clear plastic delivery
tube at bench height. In this manner, the
280 C.J. Baker
Fig. 19.2. A filled soil bin being transported.
Fig. 19.3. The ‘tillage bin’ with soil bins arranged end to end ready for drilling (from Baker, 1969a).
exact number of seeds sown was known to
make accurate counts of germination percentages.
With the ‘tillage bin’ elevated to
bench height, this allowed instrumentation
to be inserted from beneath or beside the
soil to monitor variables such as vertical
and/or lateral soil forces resulting from the
passage of individual openers.
It was occasionally necessary to test
openers operating on actual field drills. In
this case, the open-ended steel bins were left
embedded in the soil after pulling them in
with a tractor and the stirrup-shaped cutter.
A field drill was then operated over them
while they were in situ, taking care to avoid
contact with the steel side walls of the bins.
The soil bins could then be removed to controlled
climate facilities.
The ‘tillage bin’ facility successfully
allowed an accurate measure of how different
shapes of no-tillage openers and slots
respond to different soil conditions in terms
of their abilities to promote satisfactory seed
germination and seedling emergence. Almost
all previous no-tillage experiments had used
field conditions reporting successful establishment,
but the results may have been as
much a function of favourable conditions
as of mechanical performance. While field
experiments served to demonstrate that
no-tillage seeding could work, there was a
need to identify and eliminate the causes of
failures. This required precise control to be
exercised over the seeding conditions.
The tillage bin facility, because of its
moving gantry, was also used for a variety
of other related experiments. Among these
were a study of spray droplet dissipation
in pasture (Collins, 1970; see Chapter 12),
monitoring of seed spacing from precision
spacing planters (Ritchie and Cox, 1981;
Ritchie, 1982; Carter, 1986; see Chapter 8)
and the transplanting of cabbage seedlings
into untilled soil (Pellow, 1992).
The micro-environment within and
surrounding no-tillage seed slots
To learn the environmental requirements
of seeds and seedlings within the seed slot,
the following variables were tested to define
the effects of opener designs: (i) soil moisture
regime within the slot; (ii) soil-air humidity
within the slot; (iii) soil oxygen within and
around the slot; and (iv) soil temperature
within the slot.
No attempt was made in these experiments
to monitor the presence of allelopathic
substances from decaying residue or
other root material in the slot, since this
was being well researched by Lynch and
others at the time (Lynch, 1977, 1978;
Lynch et al., 1980). However, later experiments
on wet soils by the authors and their
colleagues added knowledge about these
effects and how they might be avoided
through opener design (see Chapter 7).
Soil moisture regime within the slot
Most non-destructive devices for measuring
the liquid water content of soil sample a
reasonably large soil volume. This is necessary
to average the variations inherent in
small soil volumes. The slot zone left by a
no-tillage opener represents a relatively small
volume of soil, which has made monitoring
of liquid-phase moisture particularly
difficult.
Gypsum blocks and most other physical
absorption-based devices work best at the
wet, low-tension, end of the moisture range,
which made them unsuitable for experiments
with dry soils. Early designs of dew-point
psychrometers were tried, but the steep
temperature gradients at or near the soil
surface made them unreliable. Eventually,
recourse was had to destructive gravimetric
sampling, in which miniature cores of
soil (20 mm diameter × 10 mm deep) were
removed from the slot zone and oven-dried
to provide a measurement of the liquidphase
soil moisture content on a differential
weight basis. More sophisticated instruments
have become available since these experiments
were conducted.
The research showed that the liquidphase
water content of the soil in and
around contrasting slot shapes did not
greatly differ, at least in the short term, even
when there were marked differences in seedling
emergence between openers in otherwise
relatively dry soils. While this at first
Development and Technology Transfer 281
seemed anomalous, it was decided that
exhaustive testing of further alternative
devices for measuring liquid-phase soil water
was not justified. Rather, attention shifted
to the measurement of slot humidity, or
vapour-phase soil water.
Soil-air humidity within the slot
Soil physics shows that the atmosphere (air)
in soil macropores and voids forms an equilibrium
water vapour pressure with the liquid
water contained in the surrounding soil
pores. At a given temperature, the vapourphase
water in these soil spaces represents
soil-air humidity. Since soil temperature at
seeding depth does not change rapidly and
is easily measured, soil humidity became
a reasonably reliable way to measure the
water-vapour pressure of the soil atmosphere.
Choudhary (1979) first monitored soilair
humidity within no-tillage slots using an
aspirator to slowly draw quantities of air
from the slot and pass these through a dewpoint
hygrometer for a direct reading of the
relative humidity of the air sample. While
this method produced interesting figures,
the scientists were conscious that the removal
of air from the slot inevitably resulted in its
being replaced with air drawn predominantly
from the atmosphere above the soil
surface. Thus, the slot air samples only partly
reflected the humidity within the slot.
The accuracy of the method relied on
the removal rate of the slot air and the diffusion
resistance of the slot cover, which controlled
the rate that atmospheric air replaced
that being removed. A high diffusion resistance
of the slot cover, for example, might
result in the removed slot air sample being
replaced by additional slot air from further
down the slot, while a low diffusion resistance
might contain a larger proportion of
atmospheric air. As it turned out, this diffusion
resistance was later identified as an
important variable in seed/seedling survival,
but in the meantime a method was found
that sampled the relative humidity in situ
without removing air from the slot.
A modified direct-reading humidity
probe was inserted into the slot and allowed
to equilibrate with the undisturbed slot
atmosphere for at least 2 minutes. The probe
selected was originally designed to monitor
relative humidity between sheets of newsprint.
As such it was flat and thin in shape.
The point was removed and a small piece of
fibreglass filter material was wrapped over
the end to prevent soil from falling into the
sensitive probe. The filter was left behind
in the soil when the probe was withdrawn
and was not reused. Figure 19.4 shows a
humidity probe being inserted into a dry
no-tilled soil that is contained within a
climate-controlled room.
This method yielded a direct reading of
relative humidity, approximating what the
seeds experienced in the slot. The information
gathered with this technique had farreaching
consequences. The experiments
showed that no-tilled seeds could germinate
in a high-humidity slot atmosphere,
i.e. without access to substantial amounts of
liquid-phase water, a fact that was later confirmed
by Martin and Thrailkill (1993) and
Wuest (2002).
More importantly, subsurface seedlings
could survive beneath the soil for several
weeks if the slot atmosphere was maintained
at or near 100% relative humidity.
The latter observation was shown to be a
function of the diffusion resistance of the
slot cover and the humidity gradient between
the slot air and the ambient air outside the
slot. Slot cover was itself a function of slot
shape, the presence of surface residues over
the slot and the design of the opener.
Being able to monitor slot atmosphere
humidity was one thing, but being able to
control and vary that humidity for the purposes
of experimentation was quite another
matter. Even rain-protection covers were
not satisfactory since they were unable to
alter the ambient humidity of the day. Utilizing
a multi-room controlled-climate facility,
the 0.5 t blocks of soil in their steel bins
were moved after drilling into climatecontrol
rooms in groups of three. Each room
had an artificial climate in which the temperature,
humidity, light intensity, light
spectrum, day length, nutrients and, if necessary,
wind speed and direction could be
controlled. In this way, the effects of high
and low ambient humidity levels and/or
282 C.J. Baker
temperatures were varied and the effects
on the establishing seedlings measured (see
Chapter 6).
Soil oxygen within and around the slot
The main consequence of a no-tilled soil
becoming very wet after drilling is restriction
of oxygen supply to the germinating
seeds and embryonic roots. In a tilled soil,
there is much artificial loosening, which
exaggerates the oxygen regime around the
seeds for a time. In an untilled soil, seeds
rely almost entirely on the ability of the soil
to remain adequately oxygenated in its natural
state. To test a range of opener designs
to provide varying oxygen conditions with
wet soil conditions, variables of oxygen diffusion
rates, earthworms, infiltration and soil
temperatures were considered.
Several scientists have described an
oxygen-diffusion measurement technique
involving pushing a small platinum electrode
into the soil and measuring the current
passing between this electrode and a
reference electrode. The current has the
effect of reducing electro-reducible material,
in this case oxygen, at the platinum surface.
The size of the current is governed by the
rate of oxygen diffusion from within the soil
to the surface of the electrode and thus gives
an indication of the oxygen diffusion rate
(ODR) within the soil.
Most scientists agree that the ODR
values obtained with platinum electrodes are
only an approximation of what a root might
experience, but the technique provides a
relative measure of the difference between a
range of soil conditions. The advantages are
that it is cheap, non-destructive, quick, easy
and capable of sampling very small zones of
soil in the vicinity of the slot.
Chaudhry (1985) sampled ODR in a
grid pattern around the basal area of a range
of slots in a wet soil and used a computer
program to draw iso-ODR lines reflecting
the contrasting oxygen regimes generated
by the passage of no-tillage openers and the
presence or absence of surface residues and
earthworms (see Chapter 7).
Earthworm activity was a likely contributor
to the soil slot oxygen status. Mai
(1978), Chaudhry (1985) and Giles (1994)
monitored the numbers of earthworms
present in the general plot soil and those
around a seed slot. Cylindrical cores of soil
centred on the slot were extracted and earthworms
counted and weighed. Chaudhry also
Development and Technology Transfer 283
Fig. 19.4. Sampling soil humidity in the field.
monitored earthworm activity on the soil
surface by estimating the percentage of a
given area of soil that was covered with
earthworm casts. He termed this the ‘casting
index’.
Water infiltration into the slot zone was
another potential factor in providing oxygen
exchange. Relative infiltration rates were
monitored by rectangular metal boxes (infiltrometers)
inserted into the soil surface
centred on the slot (Chaudhry, 1985; Baker
et al., 1987).
Exhaustive temperature comparisons
were made by Baker (1976a) within a range
of slot configurations. Temperature is relatively
easy to measure in small discrete zones
using miniature thermometers or electronic
thermocouples. Short-term readings were by
simple mercury thermometers, while thermocouples
were used for continuous readings,
such as diurnal ambient fluctuations.
Soil Compaction and Disturbance
by No-tillage Openers
It had long been thought that a logical result
of no-tillage openers operating in untilled
soils would be progressive compaction and
restricted root growth in the slot zone. Therefore,
several studies centred on monitoring
these aspects. The parameters measured
were: (i) soil strength; (ii) instantaneous soil
pressure (stress); (iii) instantaneous and
permanent soil displacement; (iv) soil bulk
density; and (v) smearing.
Soil strength
Soil strength is traditionally assessed by
measuring the force required to push a
probe (penetrometer) into the soil. To more
closely resemble the actions of a root, the
probe ends are usually conical in shape so
that the force dissipation is radial as well
as longitudinal. Such probes, however, are
usually designed to sample reasonably large
volumes of soil and, because of the natural
heterogeneity of soil, repetitive sampling
with a single probe is common.
To get the benefits of multiple soil
probing within the confines of the slot zone,
a miniature multi-point penetrometer was
designed (Dixon, 1972; Baker, 1976a; Baker
and Mai, 1982b). This device consisted of
20 1 mm diameter stainless steel probes
mounted in a common horizontal press bar
in such a way that the vertical position of
each probe with respect to the bar could be
adjusted and clamped individually. The
press bar could be angled at any desired
position from horizontal to vertical and
was attached to a threaded shaft that acted
as the thrust mechanism, together with a
sensitive ring-shaped force-measuring device
(known as a ‘proving ring’). Two different
displacement-measuring devices have been
used to monitor the changes in diameter of
the ring. Initially, a micrometer sufficed,
but in later tests a displacement transducer
was substituted to facilitate recorded results.
The multi-point penetrometer is shown in
Fig. 19.5.
Because soil tends to flow as a plastic
body to a limited extent for several seconds
after a rigid probe is inserted, it was necessary
to insert the probes at a predetermined
and constant speed and to read the force
applied at a standard time interval after
the probe penetration had been stopped at
the desired depth (when plastic flow had
ceased). The probes were inserted at a constant
speed of penetration by rotating the
threaded shaft at a constant speed, using a
slow-speed electric motor drive, which was
immediately disconnected upon reaching the
desired depth, and then waiting 10 seconds
before reading the gauge.
To accommodate the irregularities of the
soil surfaces, the press bar was positioned
parallel to the chosen surface and each probe
was slipped through the bar until it lightly
contacted the soil surface, then clamped in
that position. Care was taken to ensure that
an equal number of probes on each side of
the central threaded shaft contacted the soil
to ensure, as nearly as possible, symmetry
of forces about the central point when all of
the probes were pushed into the soil. Even
then, a single probe would occasionally
contact a stone, greatly distorting the symmetry,
and the readings were discarded.
284 C.J. Baker
Using the tillage bin facility previously
described, the multi-point penetrometer
was inserted from a number of directions:
(i) from above the ground to test soil strength
vertically downwards at the base of slots
(Baker and Mai, 1982b); (ii) from the side
perpendicular to the side walls of slots (Mai,
1978; Baker and Mai, 1982b); (iii) from
beneath the bins pushing upwards to measure
the resistance of slot cover to shoot
emergence (Choudhary, 1979); and (iv) perpendicular
to the cross-sectional end faces
of soil blocks in their bins to test the soil
strength in a grid pattern surrounding a
cross-section of the slots (Mitchell, 1983).
The penetrometer was not usable in the
field as its high sensitivity required a very
stable base from which to derive the penetration
force. This could only realistically
be provided by the tillage bin supported on
Development and Technology Transfer 285
Fig. 19.5. A multi-point penetrometer attached to a ‘proving ring’ force-measuring device (from Baker
and Mai, 1982a).
a concrete floor. Even then, a person pressing
on one of the bins could cause the penetrometer
reading to deflect.
Instantaneous soil pressure (stress)
As the opener passes through the soil, pressures
are created to move the soil aside, with
multiple potential consequences from compaction
to smearing. These pressures were
measured using a specially designed diaphragm
pressure pad (Mai, 1978). A small
length of 9.5 mm diameter brass tube had a
rubber diaphragm attached to one end. The
other end had a sensitive electronic miniature
pressure transducer attached. The tube was
filled with water to act as a non-compressible
liquid and a small bleed screw was used to
expel all air. These tubes were inserted
through holes in the sidewalls and base of the
steel bins into close-fitting pre-bored holes
in the soil so as to position the rubber diaphragm
in intimate contact with soil a set distance
(as close as 10 mm) from the expected
pathway of a no-tillage opener to be tested.
Since each opener travelled a wellcontrolled
pathway on the tillage bin tramway,
it was possible to very accurately
predetermine the side position of the soilstress
devices. The depth of penetration of
each opener was somewhat less predictable,
despite common ground-gauging wheels
being used with each opener, because the
ground surface of each bin did not finish
exactly the same distance from the base of
its steel bin during the field extraction process.
Thus, somewhat more latitude was
allowed for vertical positioning.
Even so, the water-filled tubes were
used to protect the expensive miniature pressure
transducers in the event of mechanical
contact with a passing opener. The brass
tubes and their rubber diaphragms were
considered expendable in the event of an
accident. The expensive pressure transducers
were not. Figure 19.6 shows one such
tube. In this manner, the contrasting instantaneous
soil stresses created by a range of
passing openers in an untilled soil were
monitored and reported (Baker and Mai,
1982a).
286 C.J. Baker
Fig. 19.6. A soil pressure measuring tube (from Baker, 1969a).
Instantaneous and permanent soil
displacement
This was measured by placing small vertical
probes in the soil at predetermined distances
from the anticipated pathway of an opener
to be tested in the soil bins on the tillage bin
(Mai, 1978). A light non-stretchable thread
was attached at one end to each probe and
at the other end to a small electronic displacement
transducer, which recorded both
the instantaneous horizontal displacement
of the soil as the opener passed and the
permanent displacement after it had passed.
The displacement data gave a measure
of the direction in which an opener displaced
the soil, as well as the plasticity of
the soil and how it had responded to the
mechanical action of that particular opener.
Soil bulk density
This was measured by extracting small soil
cores (10 mm × 10 mm) from the slot zones
in a location and pattern required by the
specific experiment (Mai, 1978; Chaudhry,
1985). The cores were weighed and a standard
procedure was used to calculate soil bulk
density as the weight per unit volume of soil.
Smearing and compaction
This was a difficult parameter to accurately
quantify, since smearing, in particular, was
often confined to a layer less than 1 mm
thick. It was determined that smearing in
any case only affected root growth when it
was allowed to dry and become a crust.
Other environmental parameters determine
slot drying, as previously described. Thus, no
effort was made to develop a direct method to
accurately quantify smears. It appeared that
the difference between a smear and a compacted
layer was only a matter of thickness.
Locating Seeds in the Soil
Three aspects of seed position within the soil
were considered important to the design of
no-tillage seed drills and planters (Ritchie,
1982): (i) seed spacing along the row; (ii)
seed depth; and (iii) lateral position of the
seed relative to the centre line of the slot.
Seed spacing
Measuring seed spacing is relatively simple.
At least, it is if no account is taken of seed
bounce in the slot and other soil factors,
such as cloddiness. Accurate measurement
can be achieved by simulated drilling, which
involves moving a seeder over a sticky plate
or paper so that the seeds dropped from the
seeder are immediately fixed on the paper
as the machine moves forward. The tillage
bin and moving gantry described earlier were
ideal for this function (Ritchie, 1982; Carter,
1986). Seed spacing can also be determined
directly by measuring the distance along the
surface of the soil between emerged seedlings.
The latter method takes no account of
displacement of shoots from the original
positions of the seeds (by, for example, weaving
around soil clods or stones) or of failure
of seeds to germinate or of seedlings to
emerge.
Seed depth
Measuring seeding depth is a deceptively
difficult problem. For obvious reasons, the
position of seeds in the vertical plane in the
soil can only be determined after they have
been sown, unlike horizontal seed spacing,
which can be simulated on sticky paper without
the opener having to penetrate the soil.
The problem is that when scientists
excavate the soil to find individual seeds, it
is almost inevitable that other seeds in the
vicinity will be disturbed. In recent years,
scientists have used one of four approaches:
Manual excavation (Hadfield, 1993;
Thompson, 1993)
Despite the disadvantages, careful excavation
of the soil in the field to expose individual
seeds is still the most common method.
This method has the problem that inherent
Development and Technology Transfer 287
errors are difficult to quantify and correct.
With tilled soils, the seeds are approached
from above, but, because of the lack of disturbance
and the relative stability of some
untilled soils and slots, it is sometimes possible
to cut a trench alongside and approach
the seeds from the side, which reduces the
risk of disturbing other seeds.
Scoop sampling
A semi-cylindrical horizontal core of undisturbed
soil, which centres on a drilled row,
is removed with a specially shaped scoop,
and then carefully split open on a bench in
a laboratory to expose the seeds (Baker,
1976a). This technique can only be used
with untilled soils because tilled soils are
too friable and the cores collapse. It is somewhat
more accurate than manual excavation
from above because the seeds are approached
from the side. It is also more convenient than
field sampling from the side because the
operator works mostly at bench height and
the soil samples can be laid on their sides
on the bench. The technique removes relatively
short lengths of row at a time, and
transports these to a laboratory. It is more
time-consuming than other methods. It is
more useful for locating and counting seeds
and seedlings in a given length of row than
for accurately recording their positions relative
to the soil surface.
Tracing down seedlings
After emergence of seedlings, careful tracing
down from the emerged shoots to the seed
position will establish the original position
of sown seeds within the soil (Stibbe et al.,
1980; Pidgeon, 1981; Allam and Weins, 1982;
Choudhary et al., 1985). This procedure has
been mechanized for automatic recording to
provide measurements for relatively large
numbers of seedlings. But, because it only
measures the emerged seedlings, it fails to
record any position for non-emerged seeds.
Since identifying disadvantaged seeds was
one of the more obvious aims of locating
them in the soil for no-tillage studies, the
technique has had limited application.
X-ray imagery of seeds
By coating seeds with red lead oxide (a
common bird repellent) prior to sowing,
images of the seeds can be recorded by
X-raying samples of soil removed from the
field in metal boxes using a veterinary X-ray
facility (Campbell, 1985; Choudhary et al.,
1985; Praat, 1988; Campbell and Baker,
1989; D. de Kantzow, 1985, 1993, personal
communication). Both aluminium and steel
are suitable for the boxes, as X-rays readily
pass through these metals without an image.
The technique is non-injurious to the seeds
(they will germinate after X-raying) and it
positively identifies seeds beneath the soil
without disturbing them. It is also largely
unaffected by soil type, moisture content or
organic matter levels, but it is best suited to
large seeds and relatively small numbers of
samples because it is time-consuming and
relatively expensive.
X-rays are derived from a point source
on the X-ray machine; thus, as the X-rays
scan a sample, a parallax error is created at
all positions except those directly beneath the
point source. This parallax error increases
towards the extremities of the sample and
affects the accuracy of quantifying the distances
between individual seeds or between
seeds and the surface of the soil. Campbell
(1985) derived a mathematical correction
for this error. He also used a strip of lead
soldering wire to indicate the position of
the soil surface in the X-rays. Figure 19.7
shows pea seeds coated with lead oxide
X-rayed beneath the soil after seeding.
Lateral position of seeds relative to the
centre line of the slot
As with seed depth, manually locating the
lateral position of seeds after they have been
drilled presents problems arising from the
possibility of inadvertently displacing them
before their positions can be recorded. Both
scoop sampling and X-ray imagery were used
on the few occasions this parameter was
studied.
To date, no totally satisfactory method
has been devised to positively, cheaply
288 C.J. Baker
and repeatably identify the final threedimensional
position of seeds in the soil.
Perhaps this accounts for why most designers
of furrow openers and seed drills seem to
satisfy themselves with defining how well
their openers follow the ground surface,
with the implied assumption that final seed
placement is solely related to this capability.
Seed Travel within No-tillage Openers
The pathway seeds are required to travel
through and from no-tillage openers is often
more tortuous and less predictable than
with simpler openers for tilled soils. Thus,
it has been important to monitor seed travel
and to analyse the causes of blockage or
disruption to the flow.
All of the techniques adopted by the
authors have involved use of video camera
and slow replay facilities. Ritchie (1982)
studied discharge of seeds from precision
singulation seeders, together with a range of
delivery tubes, by videotaping the seeds as
they fell. He calculated the delay times
between passage of successive seeds past a
grid and the resulting potential variations
in horizontal spacing along the row. The
video was then replayed on a frame-byframe
basis against a background grid calibrated
on both a time and distance basis.
Figure 19.8 shows seed ejection being monitored
in this manner using the tillage bin
moving gantry as the source of seeder
movement.
One study of seeds within the disc version
of a winged opener involved substituting
a clear Plexiglas disc for the normal
steel disc on the opener and videotaping the
seed pathway through the transparent disc.
This opener is somewhat unique in that
much of the internal pathway for the seeds
involves a three-sided tube in close proximity
to a revolving disc. The rotation of the
disc forms one wall of this delivery tube
and moves continuously. Scientists wanted
to study the influence of this moving wall
and the geometric shape of the stationary
walls on seed drop and ejection from the
opener. Figure 19.9 shows the seed flowing
through such an opener.
To date, no satisfactory technique has
been found for viewing seeds as they emerge
from an opener beneath the soil, although
knowledge of such action would assist
greatly in designing openers with improved
Development and Technology Transfer 289
Fig. 19.7. Pea seeds coated with lead oxide X-rayed beneath the soil after seeding
(from Campbell and Baker, 1989).
seed ejection and depth control qualities.
The advent of endoscopes and laparoscopes
appeals as a possibility, but dust collection
on the lens while operating beneath the
soil would seem to be inevitable, and
continuous dust removal, by, for example, a
small jet of air, might interfere with the seed
ejection process itself. None the less, there
is potential for innovative design in the pursuit
of this objective.
290 C.J. Baker
Fig. 19.8. The ejection of seeds from a no-tillage opener being filmed on video. Four individual maize
seeds can be seen dropping from the precision seeder at the centre right of the photograph.
Fig. 19.9. Seed flow being monitored through a clear Plexiglas disc.
Drag on a Disc Opener
The disc version of winged openers, in particular,
operates on the principle of a central
vertical disc with a number of other
components rubbing on it, creating a drag
on the disc, resisting turning. Contact between
the disc and some of these components, e.g.
the left- and right-hand side blades and scrapers,
is essential to the residue-handling
and seed-placement functions of the
opener. So, too, is continued and uninterrupted
rotation of the disc. Thus, it became
important to be able to quantify the magnitude
of the various torsional drag forces
opposing continuous rotation of the disc so
that those that are unnecessary might be
eliminated and those that are useful could
be minimized.
The method adopted consisted of designing
a special test stand in which a single
opener was mounted in such a way as to
allow each of the components contributing
to torsional drag to be individually attached
and removed without otherwise affecting
the function of the opener (Javed, 1992).
The test stand with opener attached was
pulled through a range of test soils at a constant
and known ground speed. The disc
had a modified motorcycle disc brake assembly
attached to it, which was capable of
stopping the disc, resulting in 100% disc
slip in the soil. The force required to achieve
any intermediate and predetermined degree
of braking of the disc was recorded by an
electronic force transducer mounted between
the disc brake assembly and the frame of the
test stand. The speed of the disc, in revolutions
per minute, was indicated by a tachometer
and was directly proportional to disc
slip in the soil at any given forward speed.
Figure 19.10 shows the disc drag test stand
and opener.
The free disc, i.e. without any torsionally
dragging components attached, was first
braked down to a predetermined speed,
representing a set amount of disc slip in the
soil. Then each of the components thought
to cause torsional drag was added to the
opener individually and measurements were
taken of the residual braking found necessary
to achieve the same set amount of disc
slip. The difference between this and the
original reading represented the torsional
drag on the disc attributable to the added
component. Variability of the soil that provided
the tractive forces driving the disc
required that a large number of recordings
Development and Technology Transfer 291
Fig. 19.10. A test stand for monitoring disc drag of a no-tillage opener.
be made to develop accuracy. These were
made using a high-speed electronic data
logger, which recorded some 10,000 individual
readings per test.
Accelerated Wear Tests of
No-tillage Openers
The disc version of the winged opener was
quite different from other seed drill openers
for either tilled or untilled seedbeds. Thus,
little was known about the relative wear rates
of its essential components, although Baker
and Badger (1979) had studied aspects of wear
on earlier simple winged openers. The two
most important areas of wear on this opener
were considered to be the soil-to-metal wear
on the outside of the side blades and their
wings and the metal-to-metal wear between
these side blades and the rotating disc.
Indeed, it had not yet been determined
whether the side blades actually rubbed on
the disc (metal-to-metal contact) or were
held fractionally clear of the disc by a fine
film of soil passing between the two components,
in which case the contact would result
in metal-to-soil-to-metal wear. The question
of possible contact between the side blades
and the disc was important because, if there
was no direct contact, it would allow the
side blades to be manufactured from material
of considerably greater wear resistance.
If there was direct contact, hard side blades
might have eroded the discs themselves,
which would have been unacceptable.
A technique was developed to examine
both questions (Brown, 1982; Brown and
Baker, 1985). A single opener was assembled
in such a manner as to electrically isolate
the side blades from the disc. It was
then operated in the soil with leads connected
to both the disc and side blades
through a 12-volt battery to complete a circuit
if the two made electrical contact and
monitored by a meter or resistance light
bulb. In the soils tested, a thin film of soil
continually isolated the blades from the disc.
Subsequent field experience confirmed that
the hardness of blades had no effect on the
life and integrity of the face of the disc, and
that the abrasion patterns on both the disc
and insides of the blades are consistent
with metal-to-soil-to-metal wear.
None the less, the thin film of soil wears
both components at this interface. A further
technique was developed to accelerate wear
testing of alternative strategies for prolonging
the life of the side blades. The opener
was modified so that the axle of the disc
could be powered, causing it to rotate when
the opener was stationary. The modified
opener was arranged so that the base of the
disc and blades were immersed in an open
box of crushed (and, in one case, slurried)
soil at normal sowing depth. The side blades
were held against the disc with springs to
simulate the forces experienced in the field
if the opener was proceeding forwards. The
test stand was left to run continuously in
this manner for extended periods so as to
monitor the pattern of wear at the interface
between the blades and the disc. Figure 19.11
shows the accelerated wear box and test
opener.
Where normal field wear patterns on
the outside of the blades and wings were
being studied (soil-to-metal wear), there was
no substitute for continuous field drilling.
By definition, the openers were required to
experience continuously undisturbed soil;
thus, re-drilling the same area repeatedly
was not an option. In one test, a single-row
drill was constructed and 16 hectares of
undisturbed land were drilled in single
rows. The opener covered some 500 km,
which was equivalent to 225 hectares of
continuous drilling with a 4.5 metre (15
foot) wide drill. Wear of the various blade
treatments was measured both dimensionally
and as weight loss (Brown, 1982; Brown
and Baker, 1985).
Effects of Fertilizer Banding
in the Slot
A number of experiments were conducted
to determine the most appropriate position
to place fertilizer separately from seed.
Apart from the more common field experimentation
techniques (which are not
described in detail here), a number of
292 C.J. Baker
specialized experimental facilities were
developed.
Horizontal, vertical or diagonal separation
directions were compared using modified
disc-version winged openers with
side-blade combinations as follows:
1. The side blades were on opposite sides
of the disc and of equal length (horizontal
separation).
2. The side blades were on opposite sides
of the disc but the fertilizer blade was
20 mm longer (diagonal separation).
3. One side blade was extended below the
disc to create a deep band beneath and to
one side of the seed (deep banding).
4. A short and a long side blade were both
positioned on the same side of the disc (vertical
separation).
Crop performance and seed damage
were compared with field trials of these
combinations. The horizontal option performed
better than the diagonal or vertical
options in all respects (see Chapter 9). This
was fortunate, because the vertical option
would have been difficult to implement on
a field scale because the placement of two
blades on one side of the disc would have
been a difficult engineering task for other
than experimental purposes. Figure 9.4
(Chapter 9) shows the experimental vertical
placement opener.
Surprisingly, the extended diagonal
option did not seem to interfere with the
ability of the opener to handle surface residues,
but it did cause undesirable wear patterns
on the inside edges of the blades
because each blade contacted the disc in the
gullet zone for approximately half of the
time, whereas contact was continuous if
above the gullets. Longer blades also resulted
in an increase in torsional drag on the disc
because of the extended contact zone
between the two. Since there was no benefit
for the longer, more complicated, fertilizer
blades, the option was not pursued.
Afzal (1981) studied vertical versus
horizontal placement of fertilizer relative to
seed without using an opener by extracting
small blocks of undisturbed soil from the
field and placing these in pots and boxes.
For vertical placement, he bored small
holes vertically into the soil, placed a preweighed
amount of fertilizer in the base of
the hole and replaced a known quantity of
loose, tamped soil on top.
For horizontal separation he repeated
the process described above but bored the
Development and Technology Transfer 293
Fig. 19.11. An accelerated wear box for testing a no-tillage opener.
vertical hole only to the seeding depth and
covered the seeds with the plug of undisturbed
soil. He then bored a horizontal hole
from the side of the pot or box to position
the fertilizer a predetermined distance from
but at the same height as the seed. This hole
was also closed using a plug of undisturbed
soil, but in this case without surface residues.
Prototype Drills and Management
Strategies
As part of the logical development of a new
field technology, laboratory developments
eventually need to be tested on a field scale.
With seed drills and planters, this can only
be partially achieved using small experimental
machines. For example, one of the
most important functions of no-tillage drills
is the ability to handle surface residues. A
single-row experimental machine might
suggest how well an opener would perform
this task, but only a machine with multiple
openers would experience interactions of
adjacent openers over a field with variable
residue amounts and configurations. Thus,
it is important to observe opener and drill
performance on a field scale along with
monitoring component wear and durability.
It is also necessary to compare different
opener design performances on a field basis,
but only after testing their biological performance
in controlled laboratory conditions.
When laboratory details are complete, appropriate
field comparisons are possible using
a test machine with several openers.
Operation in the field offers opportunities
to monitor farmer reaction to the new
technologies and to learn from farmers the
constraints imposed by their management
systems. It also allows the scientists, working
with innovative farmers, to evolve new management
strategies based on the increased
capabilities of no-tillage and related emerging
new technologies.
The development sequence involves
testing: (i) single-row test drills; (ii) universal
toolbars for field-testing several different
designs of openers at the same time;
(iii) plot-sized field drills and planters; and
(iv) field-scale prototype drills and a drilling
service for farmers.
Single-row test drills
A range of single-row drill designs were
constructed for three objectives. First, they
were a facility to test the mechanical performance
of prototype openers in a field soil.
Usually, the scope of such tests was focused
on quantifying the mechanical functioning
in different soil or residue conditions.
Occasionally, as previously described, they
may be used to drill an extended area for
accelerated wear tests.
Generally, these single-row test drills
consist of an opener rigidly mounted in a
subframe attached to a tractor three-point
linkage, with the downforce provided by
removable ballast. In this manner, the tractor
three-point linkage acted as the articulating
drag arms for the opener, although
the geometries of such linkages were seldom
adjustable to form a perfect parallelogram.
Within the limited range of vertical movement
required of the test machines when
the opener was in the ground, the tractor
linkages were considered acceptable.
Secondly, single-row units were used
for seeding purposes, at which time simple
seed and fertilizer distribution systems were
added to the basic machines. These simple
drilling units offered field experience for
verifying the laboratory biological performance
of seed and fertilizer placement.
Thirdly, they became a convenient,
although limited, machine to demonstrate
the new opener capabilities to farmer groups
without the need to transport heavy multirow
machines to the field. But developers
learned that, even with the aid of being
able to see how each opener operated on the
single-row demonstration drills, few observers
were able to visualize the capabilities
of a full-sized multi-row drill operating in
the same circumstances. Consequently, the
single-row demonstration concept played
only a minor role in the wider technology
transfer process, but was important in the
engineering development process.
294 C.J. Baker
The single-row no-tillage drill concept
was extended to become a commercially
available machine as a plot drill for experimental
stations; as a commercial drill for
establishing edible shrubs by no-tillage on
steep and erodible land; and as a commercial
drill for small farmers in developing nations.
The adaptability was further enhanced with
the provision of a wheeled front steering
frame to ensure that the wing angle on the
opener remained correct and to facilitate
turning corners when draught animals were
used. A platform was added to the rear to
allow an operator to step on or off to act as
the downforce ballast. Figures 19.12, 19.13
and 19.14 illustrate several single-row test
machines used to test and/or demonstrate
the disc version of winger openers.
Simultaneous field testing of several
opener designs
It is difficult to conduct a valid test of contrasting
openers on a field scale without the
ability to control the soil and climatic conditions.
Almost invariably, such tests reveal
the dominance of one opener over others
being compared in that particular set of
conditions, only to have the order altered in
different conditions. The field conditions
must be carefully identified under which
any one opener is dominant, to learn the
strengths and weaknesses of contrasting
designs.
Often several parameters may vary,
making it very difficult to isolate the reasons
for one or more openers being superior
for that particular set of conditions, without
results from laboratory experiments that
provide the biological capabilities of various
no-tillage openers. And, unless the openers
require very similar toolbar controls or are
self-controlled, a single setting of height,
down-pressure or speed may not be appropriate
to all openers, biasing the results
towards those openers that benefit most
from the test settings.
It is interesting that, when people are
asked to comment on the pros and cons of
various no-tillage machines, many believe
that such judgements cannot be made until
several machines are lined up beside each
other and tested in the same field. This seemingly
obvious answer, however, is flawed
because such field tests do not usually identify,
let alone isolate, the individual causal
processes of any differences that do arise. It
Development and Technology Transfer 295
Fig. 19.12. A commercially available single-row no-tillage drill.
is doubtful if any scientifically useful purpose
has ever been served by field comparisons
of multiple no-tillage machines.
Field toolbars are useful as an intermediate
stage in the engineering field testing
and development of prototype openers before
any are considered sufficiently promising
to incorporate into either a multi-row drill
or planter, or even a self-contained singlerow
drill.
Figure 19.15 shows a universal field
toolbar for evaluating a variety of openers,
296 C.J. Baker
Fig. 19.13. An early single-row demonstration unit.
Fig. 19.14. A single-row machine for testing the residue-handling capability of a no-tillage opener.
as designed by the University of New
England, NSW, Australia (J. Scott, 1992,
personal communication).
Plot-sized field drills and planters
Once the capabilities of an opener, e.g. the
disc version of winged openers, are published
or made public, it is common that
other research organizations will design and
construct plot-sized drills and planters
equipped solely with these openers to sow
test plots and fields for evaluation. In general,
most designs of the plot machines have
been an attempt to duplicate the mechanical
arrangements of commercial field machines
as faithfully as possible while at the same
time incorporating facilities to more accurately
monitor seed and fertilizer application
rates, clean the product boxes between
plots and adjust various mechanical options.
These machines are made convenient to be
easily transported to remote plots or farm
field demonstrations. Such plot-sized drills
have been an important intermediate stage
of development before full-sized field prototype
machines are contemplated. Figure 19.16
shows a selection of typical plot drills based
on the disc version of winged openers.
Several designs of plot drills were used
for plant-breeding purposes where plot sizes
were small and the quantity of seed available
was limited. Innovative mechanisms
were introduced to delay release of the seed
from the front gang of openers so that both
the front and rear gangs began and ended
seeding on the plot edges.
Field-scale prototype drills and a drilling
service for farmers
The ultimate objective of any seed drill
development programme is to produce a
field-capable machine that can prove itself
in normal commercial operation. One of the
problems in developing effective no-tillage
drills was that the drilling requirements
were largely unknown and highly variable
in this new style of farming, and few users
could identify the causes of success or failure.
Thus, field demonstration and proving
took on a new dimension.
At first, a prototype drill was transported
to a series of farmers’ properties who
were willing to try it on their farms, but this
Development and Technology Transfer 297
Fig. 19.15. An example of a universal plot seed drill.
often required modifying the hitches and
hydraulic fittings each time a new farmer
and tractor was involved. The problem of
the incompatibility of hydraulic couplings
was at first solved by equipping the test
drill with a self-contained hydraulic system
operated by a stationary petrol engine
mounted on the drill itself, but this did not
solve the other problems outlined above. It
was also difficult to find a serious commitment
from farmers to manage the no-tilled
crops in a manner to provide reliable data
on production and economics useful for
field analyses.
A successful example of prototype testing
and evaluation was a fully self-contained
tractor, drill and truck developed and transported
around New Zealand (Ritchie and
Baker, 1987). That country offered a wide
variety of agricultural enterprises, microclimates,
farming systems and soil types
representative of many of the agricultures of
the world within a convenient travelling
distance.
298 C.J. Baker
Fig. 19.16. Several plot drills based on the disc version of the winged opener.
A charge was made to the farmers to
both fund the operation and involve the
participating farmers in a more committed
and meaningful way. Thus, what was still
primarily a field testing operation for the
scientists also became a contract drilling
service for the farmers (‘custom drilling’)
and a highly effective technology transfer
process for both parties. Over a 10-year
period, during which three generations of
prototype drills were utilized, this field
drilling operation was used on approximately
200 separate fields on over 100
different properties, many of which were
drilled for a number of successive years.
Figure 19.17 shows the self-contained field
operational machine.
While the primary purpose of this prototype
drilling operation was to provide vital
field performance information for the originating
scientists and function as a technology
transfer medium, the operation became
the cornerstone for development and evaluation
of new and innovative farm management
techniques and strategies. And cooperating
scientists and consultants used the opportunity
as the means to introduce droughttolerant
pasture species into existing
dryland grasslands by other scientists (Barr,
1986; Ritchie, 1986a, b; Milne and Fraser,
1990; Milne et al., 1993).
Summary of Drill Development and
Technology Transfer
1. There are few known or standardized
experimental procedures for objectively
evaluating no-tillage technologies.
2. The study of no-tillage drills, planters
and openers requires developing knowledge
about experimental procedures, mechanical
performance and resulting plant growth.
3. Removing large soil blocks from the
field in an undisturbed state to a climatically
controlled environment is a useful
method to control soil moisture, drill with
openers to simulate field performance and
control post-drilling climate.
4. Environmental requirements of seeds
and seedlings within the seed slot involves
studying such variables as: (i) soil moisture
regime within the slot; (ii) soil-air humidity
within the slot; (iii) soil oxygen within and
around the slot; and (iv) soil temperature
within the slot.
5. Soil disturbance by drill openers
requires monitoring the parameters of:
(i) soil strength; (ii) instantaneous soil pressure
(stress); (iii) instantaneous and permanent
soil displacement; (iv) soil bulk density;
and (v) smearing.
6. Important aspects of seed position
within the soil after drilling are: (i) seed
Development and Technology Transfer 299
Fig. 19.17. A fully self-contained drilling machine for field testing and on-farm demonstrations.
spacing along the row; (ii) seed depth; and
(iii) lateral position of the seed relative to
the centre line of the slot.
7. The pathway seeds travel from metering
to and through successful no-tillage openers
is often more tortuous and less predictable
than with simpler openers for tilled soils.
8. It is important to quantify the drag forces
opposing rotation of disc openers to eliminate
those that are unnecessary and minimize
those that are useful.
9. Normal field wear of all drill components
(blades, wings, discs, bearings, etc.)
must be studied with continuous field drilling
in undisturbed soil.
10. Adding components to openers for fertilizer
placement may cause undesirable
wear patterns or interfere with the ability of
the opener to handle surface residues.
11. Field toolbars with multiple openers
are useful to field-test prototype openers.
12. The ultimate objective of any seed drill
development programme is to produce a
field-capable machine that can prove itself
in the normal commercial operation for
which it is intended.
300 C.J. Baker
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Index
Page numbers in bold refer to figures in the text; those in italics refer to tables or boxes
acetic acid 94, 162
allelopathy 23, 163
ammonia, loss from soils 126
ammonium hydroxide (‘aqua’) 125–126, 131,
132
animal-drawn equipment
knife roller 141–143
planters 212, 213
animal/crop systems, integrated 134, 169–171
animals, treading damage 170–171, 234
Argentine stem weevil 231, 233
Asia
obstacles to technical development 221
‘poverty square’ 220
small-scale no-tillage 213–225
‘auto-casting’ 57–58
automatic down force control (ADF) 111
Avena fatua see oats, wild
Avena strigosa see oats, black
The Awakening (Bevin) 5
bacteria, root 22
‘Baker boot’ 52–53, 54, 182
band spraying 176–180
equipment 180–183
Bangladesh 216, 220, 221, 224
barley crops
fertilizer placement 128–129
seed slot cover 64, 66
straw residues 97
wet soils 90, 91
bed planters 219, 222, 224
beds, permanent 224
benefits of no-tillage 11–12
carbon emissions and sequestration
19–20
crop production 13–19
energy inputs 17–19
nutrient cycling 17
soil erosion 15–16
soil organic matter 14, 15, 265–267
soil quality 16–17
soil water 15
Bevin, Alsiter 5
bio-channels 8, 118, 162
biofuels 18
Borlaug, Norman 2
brassicas 170, 270
fertilizer placement 128–129
seed metering 113–114
seeding depth 101
Brazil 209, 264
broadcasting see surface broadcasting
bullocks 221
Cajanus cajan 145
‘Cambridge’ roller 67
canola crops 121, 123–124, 229
carbon
seedling content 129–130
soil see soil organic carbon
carbon cycle 18
317
carbon dioxide (CO2)
emission measurements 258
emissions 18, 19–20, 257–261
carbon equivalents (CE) 18
carbon sequestration 18, 19, 262–263
benefits 265–267
carbon trading 19–20, 265–267
cash cropping 185
cation exchange capacity (CEC) 17
Cercosporella 244
cereal production, world 2
chaff 139, 140, 146
chemical fallow (chem fallow) 3
chemical ploughing 3
chlorpyrifos 231, 232, 233, 269, 270
CIMMYT (International Centre for the
Improvement of Maize and
Wheat) 216–217, 222, 224
clay soils 87–88
closed-circuit television (CCTV) 254
clover 175
red 100–101, 116
combine harvester 57–58
straw spreading 139, 140
compaction see soil compaction
compressed-air 109–110, 116
conservation agriculture
definition 3, 11
principles of 12–13
conservation tillage 3
contractor, no-tillage 31, 269–270, 274
controlled-traffic farming (CTF)
benefits of 236–237, 255
constraints 244
definition 236
economics 251–254, 255
field layout/system management 248–249
implications for no-tillage
operations 240–244
implications for soils and crops 244–245
machine-implement matching 245–248
planning 245
principles 245
wheel ways 249–251
costs 7, 9
capital 270–273, 276
operating 273
pasture renovation 179–180
see also economic comparisons
cotton 4, 244
cover, broadcast seed 57–58
see also slot covering
cover-crops, killing 138, 145
crop failures 7, 163, 164
crop ranges 244–245
crop residues see residue handling; residues
crop rotations 170
legume-based 264–5
rice–wheat 219
crop yields 7, 9, 13, 268, 276
comparison of disc-type openers 165
controlled-traffic farming 244, 253–254
and fertilizer placement 126–132
machine impacts 31–32, 234–235
transition phase 13, 226–227
crusting 85
CTF see controlled-traffic farming
decomposition, residues 94, 118, 143–144
seed toxicity 22, 94, 162–163
definitions in no-tillage 3–4
deflecting devices 69–71
denitrification 238
depreciation 269, 271–272, 273
depth bands 103
depth-gauging 101–103, 166
Deroceras reticulatum see slugs
diammonium phosphate (DAP) fertilizer 128,
129
dibblers (hand-jabbers) 205–206
differential global positioning system
(DGPS) 251
costs 255
diquat 2
disc-drilling 3
disc-type openers
angled 29, 41–43, 145–146, 191
comparison of function 28, 29, 163,
164–166
controlled-traffic farming 242–243
double disc 59
angled 41–43, 94, 126
offset 35, 36
seed placement problems 105, 106
slanted 40
small-scale drills/planters 208
unequal size 35–37
downforces 165, 166
residue handling 105, 150–155
hairpinning 146–147, 207, 212
scrapers 156, 157
simple design 59
triple disc 37–40, 59, 97, 128, 190, 191
wet soil operation 86, 92, 94, 95
discs
drag measurement 291–292
seed flick 105, 106
small-scale planters 207
disease 7–8, 22, 163
disease control 228
downforce 157–158, 191
control mechanisms 106–113, 116, 166
disc-type openers 165, 166
318 Index
large-scale drills/planters 190–195
power till opener 46–47
range 166
re-establishing 194–195
small no-tillage planters 206–207
variables 190
vibrating openers 50–51
drag arms 111–112, 157–158
options for attachment 191–194
parallelogram 112–113, 182, 194
stagger arrangement 157–158
stress loadings 195
drainage 7, 227, 249
draught requirements
large-scale no-tillage equipment 190, 191
small-scale no-tillage equipment 211–212
and soil strength 239
drillage 3
drilling 9, 233
dry soils 77–83
wet soils 85–89, 105, 106
drills 13–14, 100
cost–benefits of advanced 31–32, 234–235,
268, 275, 276
downforce application 106–113, 190–195
drag arms 111–112, 157–158, 191–194, 195
matching to power 198–200
operating width 185–186, 187–188, 246
pasture renovation 182–183
power requirements 189, 190, 191
product storage/metering 200–202
prototypes 294–299
reduced-till 222, 223
risk of functioning 26
selection 9
speed of operation 189
spray booms 202
surface-following 101, 106–113, 108, 114,
186–189
transport 195–198, 199
for two-wheeled tractors 222
see also openers; planters
dry soils
field experience 84
moisture loss 74–75
seed germination 76–77
seedling emergence 80–83
seedling survival 77–80
slot covering 66, 83–84
V-shaped slots 37
‘dust mulch’ 75
earthworms 6, 9, 17, 22, 227
channels 118
effects of absence 92, 94
and slot disturbance 162
soil aeration 95, 96, 283–284
and surface residues 89–90, 97
tolerance of smearing/compaction 94
wet soils 87, 88, 89–92, 95, 96
economic comparisons (no-tillage/tillage) 30–31
controlled-traffic farming 251–254, 255
cost–benefits of advanced
machinery 234–235, 268, 275, 276
Europe 275–276
levels of no-tillage 268
misleading factors 268–269
New Zealand 269–275
summary 276
economic risk 29–32
energy use 17–19
carbon equivalents (CE) 18
fuel 6, 18–19, 268–269, 271
environmental sustainability wheel 15
experimental techniques/procedures
disc drag measurement 291–292
fertilizer banding assessment 292–294
opener accelerated wear test 292, 293
plant responses to no-tillage 278–281
prototype drills and management
strategies 294–299
seed placement assessment 287–288
seed travel within openers 289–290
slot microenvironment
assessment 281–284
soil compaction/disturbance 284–287
expertise, availability 9, 274
eyespot 244
fallowing, chemical 174–175
farmers
benefits of soil carbon storage 265–266
perceptions of no-tillage 21, 185–186
valuation of forage crops 168–169
Faulkner, Edward 5
fertilizer
soil nitrogen losses 126, 263–265
storage hoppers 200–202
toxicity to seeds 24, 29, 119–120, 129
fertilizer placement 5, 8, 9, 23, 118–119,
232–233
banding 120–121, 128–132, 133, 163
seed-fertilizer distance 131, 132
vertical versus horizontal 121–126
broadcasting 118, 119, 120, 126–128,
232–233
comparisons of drill/openers 28, 29, 165
costs 228, 276
crop yields 126–132
disc-type openers 40, 126
experimental studies 292–294
metering devices 210–211
Index 319
pastures 119, 179–180
‘skip-row’ method 128–129, 129–130, 163
small-scale no-tillage 208
winged opener, disc-version 55, 56,
121–123, 125–126
fescue, tall (Festuca arundinacea) 173–174
field appearance 9
field layout 248–249
flail mower 144–145
forage crops 168–169
see also pastures
‘fuçador’ plough 212
fuel use 6, 18–19, 268–269, 271
fungal hyphae 261
furrowers 49–50
Gaeumannomyces graminis see take-all
gas-over-oil systems 109, 110–111, 116
gauge wheels 101–104, 116, 189
gauge/press wheels 55, 56, 68, 103, 189
genetically modified crops 3
germination see seed germination
global positioning systems (GPS) 240, 241, 251,
252
costs 252, 255
glomalin 261
Glycine max see soybean
glyphosate 2, 180, 231, 232
costs of use 270
crop resistance 3
timing of use 269
grasses
fertilizer placement 119, 179–180
residues 90
seed metering 113–114, 183
see also pastures
grazing 134, 170–171
‘green bridge’ concept 22
Green Fields Forever (Little) 1
greenhouse gases 257
contribution of agriculture 257
nitrous oxide 263–264
trading of credits 265–267
see also carbon dioxide (CO2)
‘Ground Hog’ 231
guidance systems 240, 241, 251, 254–255
costs 252, 255
hand-jab planters 205–206
‘happy seeder’ 219, 220, 225
harrows
slot covering 69, 70, 71
‘straw’ 139–140
herbicides 2, 8, 27, 29, 138
band spraying of pastures 176–183
costs of use 270
factors in effectiveness 27, 29
planning use 232
selection 227
timing of use 269
hillsides 16, 42, 165, 201, 212
hoe-type openers 43–46, 59
bounce 105–106
downforce requirements 191
fertilizer placement 130, 131
pasture renovation 176, 177
residue handling 45–46, 145–146
seed placement 105–106
seedling survival 78
slot covering 68, 69–71
soil disturbance 105
wet soils 86–87, 91, 92, 93, 94–95, 97, 98
hoppers, product 201–202
India 216, 220
infiltration 6, 17, 162
measurement 284
wet soils 97–98
inputs
energy 17–19, 268–269, 271
reduction 13
insecticides 201–202
integrated animal/crop systems 134, 169–171
inverted-T-shaped slots 35, 51–56
biological risk 28
covering 161
depth control 103
dry soils 84
humidity loss 63, 64, 79
micro-environment 23
pasture renovation 182–183
pressing 83
principle of 51
retention of gases 126
seed germination 77
seed–fertilizer separation 121, 122
seedling survival 78–79
soil-to-seed contact 162
wet soils 87–89, 90, 91, 92, 97, 98
irrigation requirements 6
kale 66
‘knee-action farming’ principle 230
knife rollers 141–145
Kyoto Protocol 265
labour requirements 6, 269
leaching 17
320 Index
fertilizer placement continued
legumes
crop rotations 264–265
pastures 180
seed metering 113–114
lentils 214
leveller 231
lime application 230, 231
Little, Charles 1
Lolium perenne see ryegrass
Lolium rigidum see ryegrass, annual
lucerne 65, 66, 180
lupin (Lupinus angustifolius) 4, 66, 100, 116
machine ‘tailing’ 42
machinery 7
cost–benefits of advanced designs 31–32,
234–235, 268, 275, 276
functioning of 26–27
impacts on crop yields 31–32
purchase costs 270–273
tillage
depreciation 269, 271–272, 273
retention of used 272–273, 274–275
sale of used 269
service wear 7, 165, 239, 292, 293
width-matching 245–248
see also types of machinery and equipment
macropores 63, 87, 88, 118, 162
maize
fertilizer placement 119, 120, 127–128
slot cover 65, 66
management
operator skills 229–230
pest/disease control 228
planning 230–234
post-seeding 230
prototype strategies 294–299
seeding rate 228–229
site selection/preparation 226–227
soil fertility 228, 231
weed control 227–228
Medicago sativa see lucerne
melons 244
methane 238, 264, 265
Mexico 219, 224
micro-environment, seed slot 28, 29, 161,
281–284
mineralization 118–119, 128
minimum tillage 3, 186, 275–276
moisture-vapour potential captivity
(MVPC) 63–64
mole channels 249
monsoons 215, 219
montmorillonite 87–88
mouldboard ploughing 16
and carbon dioxide emissions 19, 258–259
see also tillage (conventional)
mud, shedding from wheels 104
mulches 79–80
dust 75
and soil humidity 75
see also residues
mulching, vertical 149, 158
mungbean 224
MVPC see moisture-vapour potential captivity
narrow-row crops 160
Nepal 216, 221
nitrogen 6
availability to crops 8, 118
biological fixation 175
losses from soils 17, 126, 238, 263–265
seedling content after fertilization 129–130
no-tillage
definitions 4
terminology 3–4
nutrient availability 118–119, 238–239
nutrient cycling 17
nutrient stress 23
oats
black 143–144
wild 241
openers 34
accelerated wear tests 292, 293
bounce 105–106, 116
clearance between adjacent 156–158,
188–189
comparisons 28, 59, 164–166
controlled-traffic farming 242–243
depth-gauging devices 101–103
derivation from tillage machines 39–40
design challenges 208
downforce mechanisms 106–113, 116
furrowers 49–50
herbicide application 181, 182
horizontal slot creation 51–56
minimum disturbance 159–160
optimal performance requirements 99
pasture renovation 175–176, 176–177
raising and lowering 195–196
residue handling 145–158, 162–163
hairpinning 146–147, 207, 212, 242
risk-assessment of designs 28
seed travel, measurement 289–290
small-scale no-tillage 208–209
soil disturbance 4–5, 105, 159–163,
237–238
surface following 26, 101, 108, 186–189
and surface smoothness 227
tined 208–209, 212
Index 321
vertical slot creation 35–51
vertical travel 116
vibrating 50–51
see also types of openers, e.g. disc-type
openers; hoe-type openers
operator
small-scale no-tillage machinery 211–212
skills 7, 8–9, 166, 229–230
origins of no-tillage 2
overdrilling 4, 175, 176, 177, 178
oxygen diffusion
experimental measurement 283–284
soils 95, 96
paraquat 2, 29, 180
pastures 134–135, 171–183
fertilizer placement 119, 179–180
high-altitude 49, 50
improved 168
new no-tillage 7, 233
permanent 169
renewal 171–175
renovation 175–183
residue-handling 134–135
value to farmers 168–169
pea 81, 270
penetration forces 165
penetrometer, multi-point 284–286
permanent wilting point (PWP) 63, 75
pesticides
application/handling 8, 201–202
costs 270
timing of use 269
pests 7–8, 9, 13, 22, 163
control 228, 231, 232, 233, 269, 270
phosphorus, soil 7, 8, 238
pigeon pea 145
planning 230–234, 245
plant density 229
plant ownership 9, 272–273, 274–275
planters
animal-drawn 212, 213
hand-jab 205–206
precision 100
punch (star-wheel) 217–219
small-scale no-tillage 206–212
tractor selection 198–200
see also drills
plastic slot cover 79–80
Ploughman’s Folly (Faulkner) 5
pollution 7, 8
post-seeding management 230
potassic super-phosphate 125
potassium, soil 7, 238
poverty, Asia 215
power requirements
large-scale drill/planter 189, 190, 191
small-scale no-tillage machinery 211–212
power tillers 46–49
adaptation for small-scale
no-tillage 212–213
residue handling 47, 145, 150
seeding depth 105
stone damage 48–49
wet soils 87, 91, 92, 93, 95
precision seeders 100, 115
press wheels 39, 55, 56, 68–69, 72, 103, 189
angled 71, 72
semi-pneumatic tyres 103–104
product storage/metering 200–202
profitability, and weather variations 25
punch planters 56–57, 59, 217–219
hand-jab 205–206
operation in wet soils 90, 91, 93–94, 97, 98
‘rabi’ seed drills 216, 217, 221
radish, fodder 128–129
rainfall 25
and seedling emergence 82–83, 96
monsoons 215, 219
relative humidity (RH)
direct measurement 282
soil/slot 63–65, 161
residue farming, defined 3–4
residue handling (micro-management) 26,
145–158, 159–160
comparisons of drills/openers 28, 29, 164
disc-type openers 105, 146–147, 150–155,
207, 212
hairpinning into slot 94, 105, 146–147,
162–163, 164, 207, 212, 242
hoe/shank-type openers 45–46
pasture species 134–135
power till opener 47, 145
removing from over slot 161
scrapers/deflectors 156, 157
small planters 212
spacing of adjacent openers 156–158
winged opener (disc-version) 55–56
residues
and carbon dioxide fluxes 259–260
controlled-traffic farming 240–241
coverage levels 4
decomposition 22, 94, 118, 143–144
seed toxicity 22, 94, 162–163
and earthworms 89–90, 97
field-scale management 138–145, 159
‘long flat’ 136–137
management planning 230, 233–234
micro-management see residue handling
pastures 174
322 Index
openers continued
‘rational retention’ 214
removal/burning 134, 138, 214
rooted anchored/standing 134–136
and seed delivery 115
in small-scale no-tillage 140–145
and soil erosion 16, 25
and soil temperatures 135, 161
‘trash’ 9, 134
wet soils 90–91
‘retired’ land 171
Rhizoctonia 22
rice
dry-seeded 219
zero-tilled 214–215, 216
rice–wheat rotations 219
ridge and furrow planting 219
ridge tillage 4
risk 163
biological 7–8, 21–24, 163
chemical 27–29
comparison of openers 28, 29, 164
conventional tillage 230
economic 29–32
management 231
perception of 21
physical 24–27
rollers
knife 141–145
spiral-caged 69, 71
rolling
herbicide application 181–182
slot covering 67–68
root systems 8, 77–78
rotary tillage 46
row cleaners 147
row spacing 165
pasture/forage species 172–173, 174
runoff 15–16
ryegrass
annual 241
dry soils 82
pastures 173–174
residues 90
safety, human/biological 2
scrapers, disc-cleaning 156, 157
seed, storage hoppers 201–202
seed bounce 106, 117
‘seed burn’ 24, 29, 119–120, 129
seed covering see slot covering
seed delivery 114–116
seed drills see drills
seed flick 105, 106
seed germination 23, 76–77
and fertilizer placement 125
minimum-disturbance slot 161–162
and slot cover 64–65, 66
and soil humidity 75, 76–77
seed metering 99–100, 113–116
large-scale no-tillage machinery 200–201
pasture species 113–114, 183
precision 100, 115, 205
singulation 209
small-scale no-tillage 209–210
seed placement
opener capabilities 99
power till openers 46
surface broadcasting 28, 57–58, 90, 91, 92,
95, 96
seed quality 23–24
seed size
and metering 113–114
and seedling emergence 64–65
seed spacing 100
measurement 287
seed–soil contact 76–77, 83–84, 162
seeding depth
comparison of drills/openers 28
controlled-traffic farming 243
experimental measurement 287–288
maintaining consistency of 101–106
pasture species 182
and seedling emergence 100–101
seeding openers see openers
seeding rate 228–229, 268
calculation 229
controlled-traffic farming 243–244
seedling emergence
comparison of disc-type openers 164–165
dry soils 80–83
and fertilizer placement 121–126, 131, 132
and residues 90
and seeding depth 100–101, 116
and slot cover 64–65, 66, 162
wet soils 90–93
seedling survival
pasture renovation 176–177
and slot cover 162
and slot shape 77–80
and soil moisture 282–283
seedlings
physiological stress 23, 24
twisted 233
‘set-aside’ areas 5, 171
shank-type openers see hoe-type openers
site selection 226–227
‘skip-row’ planting 128–129, 163
slot covering 99
artificial materials 79–80
classification 60–63, 72–73
comparison of drill/opener designs 28, 164
deflecting 69–70
folding 71–72
Index 323
and humidity loss 63–65
loose (tilled) soil 61–63, 71, 72
minimum disturbance slots 160–161
pasture renovation 176, 177
pressing 68–69, 83–84
rolling 67–68
scuffing/harrowing 69, 70, 71
and seed size 64–65
and seedling emergence 64–65, 66
self-closure 106
squeezing 39, 67
V-shaped slots 38–39, 64, 66
slot shapes
horizontal 51–56
micro-environment 28, 29, 161, 281–284
pasture renovation 176–177
and seed germination 76–77
and seedling emergence 80–83
and seedling survival 77–80
and soil humidity 63–65, 79, 161
vertical 35–51
see also individual slot shapes
slugs 22, 233, 244
control 232, 233, 269, 270
small-scale no-tillage
Asia 213–215
benefits 204
characteristics 204
machinery
adapted from power tillers 212–213
animal-drawn 212, 213
for four-wheeled tractors 216–219
power requirements/ease of
operation 211–212
row-type planters 206–212
for two-wheeled tractors 220–225
residue management 140–145
smearing 85, 86, 87, 94, 162
comparison of disc-type openers 164
experimental assessment 287
snow 135
society, benefits of soil carbon storage
265–266
sod-seeding 4
soil aeration 6, 92, 95, 96, 283–284
soil bulk density, measurement 287
soil compaction 16, 86
animal treading 171
comparison of disc-type openers 164
experimental assessment 284–287
historical 5
in and around slot 37, 38, 85, 162
tolerance of earthworms 94
traffic-induced 239–240
soil conservation 12–13
soil damage 170–171
soil displacement, experimental
measurement 287
soil erosion 6, 15–16, 25, 163
soil fertility management 228, 231
soil organic carbon (SOC) 5, 12–13, 19
benefits of increases 265–267
gaseous losses 258–260
increases in no-tillage 5, 14–15, 262–263,
265–266
soil storage capacity 261
soil organic matter 6, 15, 128
soil pressure, instantaneous 286
soil quality 16–17
soil strength 8
controlled-traffic farming 237–238
experimental assessment 284–286
and nutrient availability 238–239
V-shaped slots 37, 38
soil structure 6, 9
and controlled-traffic farming 239–240
and soil strength 239
tillage 17
soil temperatures 6–7, 25, 135, 161
soil type 87–88
soil water/moisture 6, 15, 79, 161
experimental measurement 282–283
infiltration 6, 17, 97–98, 162
liquid-phase 76, 77
losses 74–75, 79
and seed germination 75–76, 125
and slot covering 63–65, 66
and soil fauna 22
soil water-holding capacity 6, 15
vapour-phase 75–76, 164
soil–seed contact 76–77, 83–84, 162
soil/slot disturbance 4–5, 105, 237–238
comparison of disc-type openers 163,
164–166
effects 160–163
maximum 160, 162
minimum 159–160, 208
soybean 4, 105, 106, 131
speed of operation 43
comparison of disc-type openers 164
large-scale machinery 186, 189
small-scale no-tillage machinery 211
spring barley 244
springs, drill/planter 106–109
‘stale’ seedbed 4
star-wheel (punch) planters 217–219
steering, automatic 251
stone damage 48–49
stover, lying 136–137
straw
chopping 139, 147–149
cutting in place 149–153
hairpinning by openers 146
324 Index
slot covering continued
lying 136–137
rooted/standing stubble 135–136
spreading 138–140
vertical mulching 149
wet versus dry 155–156
stress, physiological 23, 24
strip tillage 4, 46–49, 63, 160, 161, 212–213,
244, 264
and carbon dioxide fluxes 259, 260–261
drills 217, 218
on permanent beds 224
residue handling 145
small-scale no-tillage 222–225
stubble 135–136
stubble trampling 240
subsoiling 5, 231
surface broadcasting
fertilizer 118, 119, 120, 126–128, 232–233
seed 28, 57–58, 90, 91, 92, 95, 96
surface following 8, 26, 101, 108–109
comparison of drills/openers 28, 113, 114
downforce control 106–113, 116
large-scale machinery 186–189
surface smoothness 227
sustainability wheel 15
sustainable farming 4, 11
tailings see chaff
take-all 22
technology, transitional 221
terminology, no-tillage 3–4
tillage (conventional) 1, 34
carbon dioxide emissions 19, 257–261
costs 30–31
crop fertilizer response 118
crop rotations 170
fertilizer placement 124
history of 165, 226–227
mechanisms of soil carbon loss 262, 263
objectives 1–2
‘recreational’ 8
risk 230
seed covering 61–63
susceptibility to treading damage 170
in wet soils 89
tilled soils
fertilizer placement 126–128
moisture loss 74–75
seedling survival 77–78
structure 17
time flexibility 6
time saving 6, 7
tined openers 208–209, 212
toolbars
four-wheeled tractors 216
two-wheeled tractors 221–222
towing configurations 195–198, 199
toxicity 22–23
fertilizer–seed 24, 29, 119–120, 129
residue decomposition 22, 94, 162–163
tractors 7
four-wheeled 216–219
implement width-matching 245–248
matching with drills/planters 198–200
two-wheeled 220–225
traffic 195–198, 238
trafficability 7, 24–25
transition to no-tillage 9, 13, 226–227, 264
treading damage 170–171, 231
Trifolium pratense see clover, red
Triticum aestivum see wheat
‘turbo disc’ 37
turnips, summer 170
‘twin-track’ CTF system 246–247
tyres, semi-pneumatic (zero pressure) 85,
103–104, 116
U-shaped slots 40–51
angled disc-type openers 41–43
hoe/shank-type openers 43–46
humidity loss 63, 64, 79
pressing 83
risk assessment 28
seed–soil contact 76–77
seedling emergence 80–83
seedling survival 78, 79
wet soils 86–87, 91, 97, 98
undersowing/underdrilling 4
urea fertilizer 125–126, 131, 132
V-shaped slots 35–40
covering 38–39, 65
humidity loss 63, 64, 79
pasture renovation 176, 177
pressing 83–84
risk assessment 28
seedling emergence 80, 81
seedling survival 77, 79
slanted 40
soil–seed contact 76, 162
wet soils 37, 38, 86, 89, 90, 91, 93, 94, 97,
98
vertical mulching 149, 158
vibrating openers 50–51
walking beams 104, 116, 189
water quality 27
water table, rising 96
wear tests, accelerated 292, 293
weather 24–26, 27
Index 325
weed control 13, 227–228
chemical 27, 29, 138
controlled-traffic farming 241–242
mechanical 2, 5, 145
zero-tilled rice 216
see also herbicides
weeds 7
pastures 173–174
shift in dominant species 8, 227–228
vigour 27, 28
weights, as downforce 111, 206–207
wet soils
drilling 37, 38, 85–89, 105, 106
dry soils that become wet 89–93
infiltration 97–98
opener performance 93–98
residue management 90–91
slot cover 66
wheat
bed-planting 219
dry soils 80–81
economic risk of no-tillage
production 31–32
fertilizer placement 129, 130, 131, 132
seeding depth 100
slot cover 66
wheel ways, permanent 249–251, 256
wheels
combined press/gauge 55, 56, 103, 189
configurations 195–198
depth-gauging 101–103
mud shedding 104
press 39, 55, 56, 68–69, 71–72, 189
semi-pneumatic tyres 85, 103–104, 116
width, operating 185–186, 187–188
width matching 245–248
wildlife 135
wilting point, permanent (PWP) 63, 75
wind erosion 16
windrows, spreading 138–140
winged (inverted-T) openers 51–53
‘Baker boot’ 52–53, 54, 182
bounce 105–106
disc version 29, 53–56, 59, 128, 163, 242
herbicide application 181, 182
seeding depth 101
double/triple-shoot 53, 54
downforce and draught requirements 190,
191
drag arms 112–113
fertilizer placement 55, 56, 121–123,
125–126
pasture renovation 176–177, 182–183
small-scale design 217
wet soil function 87–90, 91, 93, 94, 95, 97,
98
wireworms 22
X-ray imagery 288, 289
Yacqui Valley, Mexico 219
Zea mays see maize
zero tillage 4
zone tillage see strip tillage
326 Index
CABI Head Office
Nosworthy Way, Wallingford, Oxfordshire, OX10 8DE, UK
CABI North American Office
875 Massachusetts Avenue, 7th Floor, Cambridge, MA 02139, USA
Cover photograph: "The ultimate in time-saving that only no-tillage
can provide - sowing a new crop as the existing crop is being harvested,
while retaining maximum residue cover throughout".
C. J. Baker, K. E. Saxton,W. R. Ritchie,W. C. T. Chamen,
D. C. Reicosky, F. Ribeiro, S. E. Justice and P. R. Hobbs
This book is a much-expanded and updated edition of a previous volume, published in 1996 as
‘No-tillage Seeding: Science and Practice’. The base objective remains to describe in lay terms, a
range of international experiments designed to examine the causes of successes and failures in
no-tillage. It summarizes the advantages and disadvantages of no-tillage in general, but takes the
view that the case for widespread adoption of no-tillage has already been made by others. The
authors have been involved in designing new equipment, but the new edition is notless promotional
of any particular product but does highlight the pros and cons of a range of features and options.
Topics added or covered in more detail in the second edition include:
 soil carbon and how its retention or sequestration interacts with tillage and no-tillage
 controlled traffic farming as an adjunct to no-tillage
 a comparison of the performance of generic no-tillage opener designs
 the role of banding fertilizer in no-tillage
 the economics of no-tillage
 small-scale equipment used by poorer farmers
 forage cropping by no-tillage
 a method for risk assessment of different levels of machine sophistication
The book represents a major resource for practitioners and academics in agronomy, soil science
and agricultural engineering.
From reviews of the first edition:
“…will be a useful addition to many libraries…interested in no-tillage techniques.”
Agricultural Science
“Did the authors achieve their aims? I believe they have done so admirably.”
New Zealand Journal of Agricultural Research
ISBN 1 84593 116 5 (CABI) 92-5-105389-8 (FAO)
2nd Edition
No-tillage Seeding in Conservation Agriculture
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ISBN included