Club of bologna proceedings

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 

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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 

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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 

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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 
 
 

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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.