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Fig. 4
– The Dowler 2 wheel drive 12 m track gantry-tractor [Courtesy Dowler Engineering,
cc
Chipping Norton, UK]
Fig. 5
– The ultimate in crop production technology? Preparation and sowing of the cropped area under a
c
gantry-based controlled traffic regime. [Courtesy James Barbour, Old Farm Bedford, UK]
79
80
Table 1
- M
ajor principal soil stresses under the wheel (or hoof!) centre with a constant mean
principal stress at the soil surface of 3.0 bar. Calculated from [15]
STRESS AT DIFFERENT
DEPTHS
(bar)
TYRE (HORSE)
DESIGN AND SIZE
LOAD PER
(HOOF) TYRE
(kg)
TYRE
INFLATION
PRESSURE
(bar)
0.2 m
0.4 m
0.6 m
850 kg horse
300/hoof (*)
2.4 bar at surface
(#)
0.41
0.11
0.05
Bias ply tyre
11.2 – 28
16.9 – 34
18.4 – 38
990
2200
2825
1.5
1.5
1.5
1.10
1.79
2.00
0.35
0.70
0.86
0.16
0.35
0.44
Radial ply tyre
11.2 R 24
16.9 R 34
650/75 R 32
710/75 R 34
1265
2600
4680
6000
1.6
1.6
1.6
1.31
1.95
2.41
2.57
0.44
0.81
1.24
1.46
0.21
0.41
0.67
0.82
Note: (*) Generous estimate, maximum load for foot rarely exceeds 30% of animal weight [16];
(#) Area in contact estimated at 0.0125 m
2
Table 2
-
The force required to tow a trailer across differently managed soil [17]
TOWING FORCE(kN)
SOIL TREATMENT
SOIL TYPE
NON-WHEELED
RANDOM
TRAFFIC
TRAFFIC LANE
Silt loam
Sandy loam
8.9
9.2
5.7
6.7
4.0
4.8
1940
199
8
81
Table 3
-
Mole plough draught and mouldboard plough specific soil resistance under different trafic
regimes on a 60% clay soil in the U.K. [1 8; 7]
PLOUGH RESISTANCE
(kN/m
2
)
YEAR
SOIL
MANAGEMENT
MOLE PLOUGH
DRAUGHT AT
550 mm DEPTH
(kN) (*)
1988
1990 (#)
1991
1993
Random traffic
Non-trafficked
29.6
25.3
107
42
47
62
125
72
135
85
Note: (*) [19];
(#) Soil conditions in were such th at conventional inputs were unusually low
Table 4
-
Cultivation operations needed and energy required for seedbed preparation under diffeent traffic
regimes in the U.K., on a 60% clay soil in spring, following autumn ploug hing [18]
SOIL
MANAGEMENT
ENERGY REQUIREMENTS FOR THE DIFFERENT OPERATIONS
(MJ/ha)
SPRING
TINE
POWER
HARROW
HARROW
DRILL ROLL
TOTAL
ENERGY
Random traffic
Non-trafficked
57
108
29
25
31
27
30
27
255
79
Table 5
-
Tillage and traffic effects on water run -off and crop yield in Queens land, Australia [20]
WATER RUN-OFF
(mm)
CROP YIELD
(t/ha)
SOIL MANAGEMENT
CONVENTIONAL
TILLAGE
ZERO
TILLAGE
WHEAT
1994
SORGHUM
1995
MAIZE
1996
Evenly trafficked (1 pass)
Non-trafficked
322
266
282
166
1.5
1.9
5.2
5.9
6.5
7.4
82
Table 6
-
Yield of winter wheat in 1994 on a 60% clay soil in the U.K. with different traffic treatments
SOIL
YIELD OF WINTER WHEAT (t/ha)
PRIMARY TILLAGE SYSTEM
MANAGEMENT
MOULDBOARD
PLOUGH
TINE CULTIVATOR
ROTARY DIGGER
Random traffic
Non-trafficked
8.5
10.1
7.4
10.0
-
10.5
Note: Least significant difference = 1.4 t/ha
Table 7
-T
rack settings and rows/m of field width for tractor and gantry systems with crop rows spaced
at 275 mm and 850 mm
MACHINE AND
ROW SPACING
(mm)
ROWS
(n.)
TRACK
WIDTH (*)
(m)
Rows/m
(n.)
INCREASE IN AREA
AVAILABLE COMPARED
WITH TRACTOR SYSTEM
(%)
Tractor on 14.9 R 36 tyres
275
850
Gantry on 16.9 R 34 tyres
275
850
6
2
28
9
2.1
2.1
8.1
8.1
2.90
0.94
3.43
1.11
18.3
18.1
Note: (*) Track width = (n. rows x row spacing) + loaded sectional width of tyre
83
DISCUSSION
Theodor FRIEDRICH
F.A.O.
If I look at some of the presentations given
today, it appears that the approach to
reducing mechanical operations or tillage is
still starting from the baseline that we need to
till, and that to make it more effective we
reduce the operations. Now as I see the
presentation of Professor Heege as saying
that the most fertile soils have been virgin
soils, and putting on top of that the
presentation of Tim Chamen now, I feel that
we should probably take a different approach
to look at reducing tillage: starting from the
baseline “we don’t have to till”, and then
saying “OK, if we want to grow a crop, what
are the minimum operations we really need to
do in order to produce our crop”. And we
have seen very clearly in Tim Chamen’s
presentation that there is a lot of waste, as he
called it, that we can actually cut out of our
systems if we take that approach.
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