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Page 1: Effects of wheel and track traffic on the soil and on crop growth and yield

Soil & Tillage Research, 19 ( 1991 ) 131-143 Elsevier Science Publishers B.V., Amsterdam

131

Effects of wheel and track traffic on the soil and on crop growth and yield

V.A. Rusanov All-Union Research Institute of Agricultural Mechanization (VIM), 1st Institutsky Proezd 5, 109389

Moscow (U.S.S.R.)

(Accepted for publication 9 July 1990)

ABSTRACT

Rusanov, V.A., 1991. Effects of wheel and track traffic on the soil and on crop growth and yield. Soil TillageRes., 19: 131-143.

The U.S.S.R. staged extensive research in various soils and climatic zones to estimate the effects of traffic on the soil, and on crop productivity. The present paper describes a long-term stationary ex- periment on the Kuban black-earth soils of medium depth and favourable physical properties. The results demonstrate that at a certain level of traffic intensity these soils fail to restore their character- istics within the required terms, even with the help of traditional practices of soil treatment, which brings about reduction in crop yields not only in the years soil compaction occurred, but also in sub- sequent years. Generalization of numerous results of otber investigations, as performed in the U.S.S.R., indicates that variation~ in crop yields depend mostly on the magnitude of the wheel and track pres- sure exerted on the soil, and on the number of passes of a wheel or a track along the same trail. It has also been found that modern machinery traffic causes a considerable increase in the resistance of soil to cultivation, and dete'doration of soil structure. When wheel and track traffic on soil is restricted in accordance with the recommendations of State Standard GOS'I 26955-86, essential reduction in its productivity does not occur.

INTRODUCTION

The investigations accomplished in the 1920s by Kachinsk3, ( !927) and Pigulevsky (1929) to estimate the effects on soil of a number of imported tractors with a mass of 2-6 t, showed substantial deterioration of soil char- acteristics. Laboratory-type experiments established that self-restoration of the damaged structure of Crimean soil required a time span of about 15 years (Pigulevsky, 1929). This kind of research was continued in the 1960s and thereafter largely as a result of the introduction of heavy-duty wheel tractors in field operations.

Over 20 years ago, the U.S.S.R. started manufacturing a heavy-duty wheel tractor with a mass exceeding that of the heaviest modem crawler tractor by 1 t, and the pressure it exerts on the soil by 150%. Within the same period the

0167-1987/91/$03.50 © 1991 D Elsevier Science Publishers B.V.

Page 2: Effects of wheel and track traffic on the soil and on crop growth and yield

132 V.A. RUSANOV

mass of trailers, combine harvesters and similar machinery increased 1.5-2.5 times. To a considerable ext~nt such a tendency in the development of agri- cultural equipment is typical of many western countries.

A series of research reports (Makarets, 1967; Gaponenko, 1971 ) has re- vealed that wheel tractors, especially those of the new generation, cause sig- nificantly higher soil compaction than crawler tractors. However, neither these, nor similar reports offer any concrete recommendations. This may be explained by the fact that, so far, such investigations have been rare, and all of them have been accomplished following different procedures, which makes generalization of the results very difficult.

Since 1973, on assignment by the All-Union Academy of Agricultural Sci- ences, research has been started by various institutes to evaluate the effects of wheel and track traffic on the soil. The All-Union Research Institute of Agri- cultural Mechanization (VIM) jointly with the Timiryasev Agricultural Academy (TAA) made use of accumulated experience to work out a special programme and techniques (VIM, 1978) involving particular procedures for evaluation of the effects of wheel and track traffic on soil physical properties, soil resistance to cultivation, and on yields of various crops on experimental fields and in field-practice tests.

To study the dynamics of the change in the fertility of black earth this tech- nique was used in a long-term field experiment which was started in 1977. The present paper reports the results of this experiment obtained during a 9- year period (Rusanov et al., 1983, 1989).

MATERIALS AND METHODS

In the experiment, which lasted from 1977 until 1985, soil compaction was accomplished with the 6.5-t crawler tractor DT-75 M, and with wheel tractors T-150K and K-701 of 8.0 and 13.7 t mass, respectively. In Treatments 1-6, after conventional tillage and prior to seedbed preparation and sowing of spring and winter crops, passes of various frequency were made (Table 1 ). To evaluate restoration of soil characteristics by ploughing, the experiment was extended to include Treatments 7 and 8, where the soil was compacted with the K-701 tractor in autumn, and Treatments 9 and l0 where the soil was compacted in spring. In these treatments, the compaction was followed by ploughing and seedbed preparation. Treatme,.t I 1 consisted of an uncom- pacted control plot. In all eleven treatments, sowing of various crops was per- fo~led by means of a broadcast sowing unit without trafficking the plots. Experimental compaction was terminated in three treatments (Nos. 3, 4 and 7) in 1981, and in all others in 1982.

The soil of the experimental plots was 60-80 cm thick, heavy-loam black eartl~ of the Kuban area. On the control plot, in all years, bulk density was between 1.10 and 1.21 gcm -3 in the tilled layer of 0-30 cm depth, and be-

Page 3: Effects of wheel and track traffic on the soil and on crop growth and yield

EFFECTS OF WHEEL AND TRACK TRAFFIC ON SOIL AND CROPS 1:33

tween 1.25 and 1.29 g cm -3 in the 30-50-cm layer. This means that on the control plot, which was trafficked only once by a crawler tractor when plough- ing, soil physical characteristics were optimal. The same crawler tractor and ploughing outfit were used for annual tillage on all other plots as well.

At the time of soil compaction and sowing of winter wheat (1977, 1983 and 1985 ) the soil moisture content in the 0-20-cm layer was below 60% of the moisture content at field capacity. When sowing spring crops, the mois- ture content of the 0-20-cm layer was between 70 and 80% of the moisture content a~ field capacity.

RESULTS

Bulk density

The data obtained demonstrate (Table 1 ) that after compaction the in- crease in bulk density in all soil layers investigated progressed with increase in pressure, frequency of passes and soil moisture content. The increase in bulk density in the 10-20-cm layer, not subject to cultivation after the com- paction, amounted to 0.25 g cm-3 in the case of one or two passes of a crawler tractor, and to 0.38 g cm -3 in the case of a wheel tractor. Below the tiffed layer the increase in bulk density after compaction by wheel tractors K-701 and T-150K was 1.5-2 times larger than after compaction by a crawler tractor.

In 1981 in Treatments 3, 4 and 9, no compaction was performed. However, in spite of autumn tillage, double cultivation of soil, and the effects of natural and climatic factors, soil bulk density in all layers was still 0.07-0.17 g cm -3 higher than on the control plot. At the same time, in the 30-40-cm layers the higher soil bulk density as compared with the control plot decreased by 50%, while no reduction in soil bulk density was registered in the 40-50-cm layer. Four years after termination of the compaction treatments, soil bulk density in the tilled layer was practically the same as on the control plot. However, in the 30-40-cm layer considerable differences in bulk density remained even after 5 years. Only on those plots, where the soil was compacted by one or two passes of a crawler tractor, the original soil bulk density was restored within one year.

Ploughing of soil compacted in autumn (Treatments 7 and 8) provided for a considerable increase in the intensity of its self-loosening, which may be explained by considerable accumulation of moisture by the loosened soil dur- ing the autumn and winter period. In these treatments also, self-loosening was more intensive below the ploughed layer. After compaction and tillage in spring (Treatments 9 and 10), soil self-loosening progressed to a consider- ably smaller extent.

Page 4: Effects of wheel and track traffic on the soil and on crop growth and yield

134 V.A. RUSANOV

TABLE !

Increase in bulk density (g cm -3 ) on compacted plots relative to the non-compacted control in the period 1978-1985

Tillage Treat-Tractor Number Depth 1978 1979 1980 1981 1984 1985 treatment ment of passes ( c m ) 06.06 30.05 02.07 20.05 27.06 02.08

Compaction 1 DT-75M 1-2 0 - 1 0 0.05 0.14 0.15 0.16 0.00 - +seedbed 10-20 0.05 0.25 0.24 0.17 0.00 - preparat ion 20-30 0.12 0.15 0.14 0.14 0.00 - ( in au tumn 30-40 0.07 0.07 0.07 0.10 0.02 0.01 orspring) 40-50 0.02 0.01 0.03 0.04 0.04 0.02

2 0 -10 0.12 0.22 0.24 0.22 0.01 - 10-20 0.17 0.32 0.32 0.24 0.01 - 20 -30 0.16 0.20 0.21 0.18 0.03 - 30-40 0.08 0.11 0.12 0.12 0.02 0.04 40 -50 0.05 0.05 0.07 0.09 0.02 0.03

3 0 -10 0.17 0.24 0.25 0.08 0.00 - 10-20 0.20 0.33 0.33 0.17 0.01 - 20 -30 0.18 0.22 0.22 0.09 0.02 - 30 -40 0.11 0.13 0.14 0.07 0.03 0.04 40 -50 0.06 0.06 0.09 0.08 0.02 0.02

4 0 -10 0.19 0.27 0.28 0.13 0.01 - 10-20 0.24 0.36 0.37 0.18 0.02 - 20 -30 0.20 0.28 0.28 0.14 0.02 - 30-40 0.12 0.18 0.18 0.09 0.06 0.06 40-50 0.08 0.10 .0.12 0.12 0.04 0.04

5 0 - 1 0 0.16 0.24 0.23 0.28 0.01 - 10-20 0.20 0.31 0.30 0.34 0.02 - 20 -30 0.17 0.20 0.20 0.25 0.03 - 39 -40 0.10 0.13 0.13 0.16 0.06 0.06 40 -50 0.04 0.05 0.07 0.11 0.03 0.04

6 0 - 1 0 0.20 0.25 0.28 0.31 0.02 - 10-20 0.23 0.36 0.34 0.38 0.03 - 20 -30 0.20 0.27 0.26 0.29 0.06 - 30 -40 0.12 0.16 0.15 0.18 0.09 0.09 40 -50 0.07 0.09 0.10 0.13 0.06 0.06

DT-75M 3-4

K-701 1-2

K-701 3 - 4

T-150K 1-2

T-150K 3 - 4

Penetration resistance

Similar results were obtained with regard to soil penetration resistance (Figs. l and 2). In the case of one or two passes of a crawler tractor (Treatment 1 ), one year after termination of the traffic, in all layers penetration resistance proved to be only insignificantly higher than on the control. In the case of Treatments 3-6, where the soil was compacted by wheel tractors, penetration

Page 5: Effects of wheel and track traffic on the soil and on crop growth and yield

EFFECTS OF WHEEL AND TRACK TRAFFIC ON SOIL AND CROPS 135

Tillage T r e a t - T r a c t o r N u m b e r D e p t h 1978 1979 1980 1981 1984 1985 t rea tment m e n t o f passes (cm) 06.06 30.05 02.07 20.05 27.06 02.08

Autumn com- 7 K-701 1-2 0-10 0.02 0.03 0.03 0.02 0.00 - paction 10-20 0.03 0.03 0.03 0.05 0.00 - +ploughing 20-30 0.05 0.04 0.06 0.07 0.01 - +seedbed 30-40 0.05 0.07 0.09 0.12 0.03 0.01 preparat ion 40-50 0.06 0.05 0.07 0.09 0.00 0.02

8 K-701 3-4 0-10 0.03 0.03 0.04 0.04 0.00 - 10-20 0.04 0.05 0.06 0.06 0.01 - 20-30 0.08 0.08 0.09 0.11 0.03 - 30-40 0.06 0.09 0.11 0.16 0.07 0.08 40-50 0.07 0.08 0.09 0.12 0.04 0.04

9 K-701 1-2 0-10 0.08 0.10 0.09 0.09 0.01 - 10-20 0.08 0.11 0.11 0.07 0.01 - 20-30 0.10 0.10 0.10 0.11 0.03 - 30-40 0.09 0.12 0.14 0.13 0.05 0.04 40-50 0.08 0.10 0.11 0.07 0.04 0.05

10 K-701 3-4 0-10 0.09 0.13 0.11 0.13 0.01 - 10-20 0.12 0.14 0.13 0.15 0.03 - 20-30 0.11 0.13 0.11 0.13 0.06 - 30-40 0.13 0.16 0.19 0.19 0.10 0.09 40-50 0.11 0.11 0.13 0.17 0.08 0.10

11 - - 0 - 1 0 1.03 1.04 1.14 1 . 1 1 1.10 - 1 0 - 2 0 i.10 1.13 !.23 1 . 2 3 !.24 - 20-30 1.18 1.20 1.25 1 . 2 5 1.24 - 30-40 1.24 1.28 L26 1 . 2 7 1 . 2 5 !.30 40-50 1 . 2 7 1.20 1.30 1.30 1.30 1.32

P=0.05 0-10 0.06 0.08 0.08 0.04 0.04 - 10-20 0.14 0.08 0.09 0.14 0.04 - 20-30 0.16 0.12 0.09 0.04 0.04 - 30-40 0.05 0.13 0.08 0.05 0.03 0.04 40-50 0.06 0.10 0.08 0.04 0.06 0.04

Spring com- paction +ploughing + seedbed preparat ion

Control

resistance regained its initial value only after 3-4 years, while in the case of Treatments 9 and l 0 penetration resistance in the 30-60-cm layer was essen- tially much higher than on the control plot even after 5 years.

Crop yield

In 1978, winter wheat yields were significantly higher (Table 2) on those plots where the increase in soil bulk density was largest (Treatment 4). This

Page 6: Effects of wheel and track traffic on the soil and on crop growth and yield

136 V.A. RUSANOV

TABLE 2

Crop yield ( 100 kg ha- ' ) on compacted plots and differences in yield relation to the non-compacted control in the period 1978-1985 ~

Tillage Tractor Treatment 1978 1980 1981 treatment No.

Winter wheat Spring barley Spring barley

CF CY RC CF CY RC CF CY RC

Compaction + seedbed preparation (in autumn or spring)

Autumn com- paction + ploughing + seedbed preparation

Spring com- paction + ploughing +seedbed preparation

Control

DT-75M 1 1 40.2 0.4 2/5 21.5 -3.2 1/6 16.0 -1.2 2 3 41.2 1.4 4/11 15.7 -9.0 3/14 13.9 -3.3

K-701 3 l 40.9 l.l 2/5 16.7 -8.0 0/5 15.4 -1.8 4 3 43.4 3.6 4/11 15.7 -10.7 0/ l l 13.6 -3.6

T-150K 5 l - - 2/5 17.5 -7.2 1/6 15.9 -1.3 6 3 - - 4/ l l 13.5 - l l . 2 3/14 13.3 -3.9

K-701 7 l 41.3 1.5 2/5 23.3 -1.4 1/6 16.5 -0.7 8 3 41.6 1.8 4/11 22.4 -2.3 3/14 16.2 -1.0

K-701 9 i - - 2/5 15.5 -9.2 0/5 16.0 - 1.2 10 3 - - 4/11 14.3 -10.2 3/14 14.1 -3.1

- 11 0 39.8 - 0 24.7 - 0 17.2 -

P=0.05 2.8 3.8 2.1

m Numerator-frequency of compaction in given year; denominator-frequency of compaction through- out all years investigated. CF, compaction frequency; CY, crop yield; RC, crop yield relative to control.

is expla ined by the fact tha t sowing was pe r fo rmed u n d e r relatively dry soil condi t ions . C o m p a c t i o n increased capil lary rise o f mois tu re f rom deeper lay- ers, which produced a favourable effect dur ing the per iod o f 2 weeks drought tha t fol lowed sowing.

In 1979, the soil was compac ted unde r wet condi t ions , and har rowing pr ior to sowing d id not result in sat isfactory loosening o f the soil. Consequent ly , few seedlings emerged and the crop failed. Poor soil loosening by harrowing on compac ted plots was also observed in subsequent years, result ing in a re- duc t ion in the n u m b e r o f p roduct ive stems, and in p lant height. Simultane- ously, in the year o f compac t ion and in subsequent years, in all t r ea tments a 5 -16% reduc t ion in the n u m b e r o f ears and in ear length was registered, as compared with the control plot.

In all years except 1978, the yield relative to the control plot, was lower the

Page 7: Effects of wheel and track traffic on the soil and on crop growth and yield

EFFECTS OF WHEEL AND TRACK TRAFFIC ON SOIL AND CROPS | 37

1982 1983

Peas Winter wheat

CF CY RC CF CY RC

1984 1985

Sunflower Winter wheat

CF CY RC CF CY RC

0/6 23.3 - 1.2 0/6 39.8 1.2 0/6 24.8 - 0 . 2 0/6 54.7 0 0/14 21.3 -3 .2 0/14 41.3 0.3 0/14 24.0 - 1.0 0/14 54.0 - 0 . 7 0/5 21.2 - 3 . 3 0/5 40.9 -0 .1 0/5 24.6 - 0 . 4 0/5 54.6 -0 .1 0/11 20.6 - 3 . 9 0/11 41.3 0.3 0/11 24.1 - 0 . 9 0/11 54.3 - 0 . 4 0/6 21.6 - 2 . 9 0/6 41.0 0.0 0/6 23.3 - 1.7 0/6 53.9 - 0 . 8 0/14 20.2 - 4 . 3 0/14 41.2 0.2 0/14 23.3 - 1.7 0/14 53.8 - 0 . 9

0/6 25.4 +0.9 0/6 40.4 --0.6 0/6 25. l 0.1 0/6 55.0 0.3 0/14 25.4 +0.9 0/14 41.5 0.5 0/14 24.5 -0 .5 0/14 54.5 --0.2

0/5 22.9 - 1.6 0/5 41.4 0.4 0/5 24.5 - 0 . 5 0/5 54.3 --0.4 0/14 20.9 - 3 . 6 0/14 40.7 --0.3 0/14 23.7 - 1 . 3 0/14 53.5 --1.2

24.5 - 0 41.0 - 0 25.0 - 0 54.7 -

4.0 1.6 1.1 1.1

more the soil was compacted. Thus, in 1980, after four passes of a crawler tractor (Treatment 2) and after two passes of the K-701 tractor (Treatment 3) soil compaction was similar, and the reduction in crop yield of spring bar- ley amounted to 0.8 and 0.9 t ha -~, respectively. In 1981, in Treatments 3 and 4, no compaction was performed, and in the 0-20-cm layer of Treatment 4 bulk density was equal to the bulk density in Treatment 1. However, the reduction in spring barley yield for Treatment 4 was three times higher than that for Treatment 1. In 1982, in all plots no compaction was performed. However, the reduction in crop yield was still higher for Treatments 3 and 4 than for Treatment 1.

Calculation of the relationship between crop yield reduction and soil den- sity increase in the 0-30-cm layer ( 1980, 1981 and 1984) and in the 40-50- cm layer ( 1985 ) showed that an increase in soil density of 0.01 g cm -3 in the

Page 8: Effects of wheel and track traffic on the soil and on crop growth and yield

138 V.A.RUSANOV

5-

: [ 0

5

~n 0

uJ

5 ,=,, I- 9.

5 Oo

DEPTH 0 - 3 0 cm

compaction only

I - - - ! r - - 7 F--1 . . . . . . . .

I II II Ir---:: : . . . . . . . . .

autumn compaction + ploughing

r - -I

~j 5

~- I - - 7 - - - ~ . . . . , z OJ ~ F 7 r "1

- spr ing compac t i on+p lough ing 5

0, ~ l I F - - - ; r - - - ~ . . . . . . . . . .

~ , . V-7F--1 - o F----I F - - ' ] . - - . . . . . . . .

1979 19~0 1981 ~902 1903 1984

YEARS

r - - - - " 3 _ w i t hou t compac t i on =-_ ~_.~

I

DT-?SM n= l - 2

2 DT - ?5M n :3 -4

3 K -701 n : I - 2

4 K - 701 n= 3 -4

?

K - 7 0 1 n= I - 2

8 K-?01 n=3 -4

9 K-?OI n=1 -2

10 K - 701 n=3 -4

Fig. 1. Changes in soil penetration resistance produced by traffic and self-loosening after ter- mination of the compaction treatments. 1-10 = treatment; n = number of passes.

5"

"T 5,

d 0

~ o ~ 5 a:

~ o ; s :E

o

~ o

_.g 5 .

g 5 z

0

DEPTH 30- 60 cm

_=.1 r'TsM

"~ r r - - . . . . . "3 n= I -2

DT2?5 M . . . . . . . 1 r-- . . . . -1 n=3 -4

3 K - ?01

. . . . . . 1 r - - - - ~ - - n= l - 2

r . . . . - - t i I r " . . . . .

if . . . . . . t f.

, I 1 , , I r . . . . - ~

! ; r . . . . . . "~ ! . . . . . . .

r - . . . . "~1 ! I I I . . . . . - - I ~ . . . . . . 1 r . . . . . . !

t I - ' - 1 r . . . . . -1 ; ' , f ; ,

1982 790,; 1905

YEARS

K-70T n=3 -4

7 K-701 n= I - 2

K-8701 n=3 -6

9 K - 701 n= l - 2

9 K -701 n=3 -4

Fig. 2. Self-loosening after compaction. 1-9 = treatments; n = number of passes.

Page 9: Effects of wheel and track traffic on the soil and on crop growth and yield

EFFECTS OF WHEEL AND TRACK TRAFFIC ON SOIL AND CROPS | 39

tilled layer resulted in 14-15 kg ha-t reduction in crop yield. The same in- crease in soil density in the 40-50-cm layer resulted in 8 kg ha- t yield reduc- tion. Similar calculations were accomplished for the penetration resistance. It was found that a 0. I-MPa increase in penetration resistance relative to the control plot brought about a crop yield reduction of 39-125 kg ha- ~.

DISCUSSION

In experiments accomplished on sod-podzolic soils in 1977-1980, where the DT-75M, T-150K and K-700 tractors were employed only for sowing in team with 3 drill units, it was found that on the plots where the T-150K and K-700 tractors had been used, yields of grain and fodder crops were lower by 8-12% and 18-20%, respectively, than on the non-trafficked control plot (Puponin et al., 1981 ).

In field-practice type experiments accomplished by VIM during 1976-1980 to evaluate the effects of three types of tractors on sugar beet and corn yields, it was established that the yield reduction increased with the ground pressure exerted by the tractors (Rusanov, 1988).

Generalization of the data obtained in model experiments accomplished in Byelorussia, Estonia, Lithuania, in the Moscow, I~ev, Voronezh and Tula re- gions, and in the Krasnodar territory has shown (Table 3) that yields ofspr~ng and winter grain and fodder crops (oats, barley, wheat, pea; fodder mixture:

TABLE3

Grain and forage crops yield reduction, as a function of ground pressure and number of tractor passes t

Tractor Ground Number Yield Coefficient of pressure (kPa) of passes reduction (%) variation (%)

MTZ 150 1 7.8 80.8 YUMZ 150 2-3 14.1 66.5

4-5 19.8 50.5

DT-75 150 1 7.5 40.0 T-74 150 2-3 13.3 62.3

4-5 : 9.2 53.1

T-150K 180 I 12.3 58.5 2-3 23.3 35.4 4-5 30.3 39.2

K-700 200 1 16.3 49.9 K-700A 200 2-3 26.8 31.7 K-701 200 4-5 35.1 28.6

tAverage results from experiments in eight regions (see text).

Page 10: Effects of wheel and track traffic on the soil and on crop growth and yield

140 V.A. RUSANOV

corn and pea, pea and oats, vetch and oats; silage corn; fodder beet) drop with increasing ground pressure and number of tractor passes (Rusanov, 1988). A single compaction by the MTZ wheel tract~' and the DT-75 and T-74 crawler tractors with a ground pressure of 150 kPa, resulted in 7-8% reduction in yield, while single passes by the T-150K and K-700 tractors with 180 and 200 kPa ground pressures, respectively, caused 12 and 16°/0 reductions in yield, respectively. An increase to two or three passes almost doubled the yield reduction.

In 1986, the U.S.S.R. approved the GOS-l's (State Standards) that speci- fied permissible effects of wheel and track traffic on the soil and safe pressures to 0.5 m depth, depending on soil moisture content and field work season. Substantiation and development of these specifications involved participa- tion of 14 institutes in the U.S.S.R.

In accordance with the GOSTs of the U.S.S.R., the pressure exerted on soil by machineD' engaged in field work at a moisture content of over 90°/o (w/w) of the moisture content at field capacity, shall not exceed the limit of 80 kPa. These soil moisture conditions usually occur in spring, when early harrowing is performed. The average results of seven experiments of the field- practice type with various types of tractors in Byelorussia, in the Moscow and Odessa regions, and in the Krasnodar territory, indicate (Table 4) that craw- ler tractors DT-74 and DT-75M, manufactured in the U.S.S.R., cause a re- duction in crop yields by I 1%, whereas yield reductions caused by the T-150K and K-700 wheel tractors amount to 20-25% (Rusanov, 1988 ).

A matter of interest is the evaluation of the effects of twin tyres on soil density and crop yield. Hard twin tyres provide only for 20-50% ground pres- sure reduction, and with the considerable non-linearity of soil deformation characteristics involved, the actual soil density reduction, even in the tilled layer, amounts to only 0.03-0.05 g cm -3. However, the results of correctly performed experiments indicate that the use of twin tyres reduces soil compaction.

TABLE 4

Grain and forage crops yield changes produced by different tractors used for sowing cereals and fod- der crops in 1980-1985

Indices Tractors with three drills

T- 150PK DT-75M T- 150K T- 150K K-700 K-700 1"-150Y8 DT-74 with twin with twin DT- ! 75S8Y :yres tyres

Ground pressure 80 160 180 136 200 135 (kPa)

Yield (%) 100 88.4 79.8 83.6 75.2 82.4

Average results from experiments in four regions (see text).

Page 11: Effects of wheel and track traffic on the soil and on crop growth and yield

E F F E C T S O F W H E E L A N D T R A C K T R A F F I C O N S O I L A N D C R O P S 1 4 1

The effect of twin tyres on crop yield is of a more complicated nature. An unambiguous answer to ff,~s question may be produced when twin tyres suc- ceed in reducing the contact pressure to the permissible level. Average results obtained in the above experiments indicate (Table 4) that twin tyre~ mounted on the T-150K tractor provide fbr an increase in crop yield by 4-7%. How- ever, in one of these experiments a reduction in crop yield was registered, while no differences were observed in another. In many cases insufficient re- duction of twin-tyre contact pressure and the increased compacted area leads to the outcome that on plots where crawler tractors were used for sowing, crop yield was higher than on plots where tractors with twin tyres were used.

In the Krasnodar territory, experiments of the field-practice type were con- ducted for 5 years to evaluate the effects of tractor traffic on variation in yields of sugar beet and corn (Rusanov et aL, 1981b). The results show (Table 5)

TABLE5

Sugar beet and corn yield reductions (%) produced by different tractors (1980-1985)

Tractor Ground Sugar beet roots Corn grain ~,ressure (kPa) Krasnodar Ukraine Krasnodar Ukraine

territory territory

T-70C 108 - - 1.7 - T-70C 162 2.8 - - - MTZ-52 219 5.1 10.2 5.8 14.0 DT-75M 240 6.1 - 8 o _

• . ._._.......--.-.-~ CONTROL

PLOT

80.

40.

" ~ o

80"

0

80 ̧

40 u I

< 5

on t rack

c raw le r

tractor" T-150

on t rack of wheel

t rac to r K- 701

1~-----~ ~-----~ r-----71------] 5- tO 10 - ;'5 15 -20 > 2 5

SIZE OF SOIL AGGREGATES (crn)

Fig. 3. Changes in soil aggregate distribution produced by traffic.

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142 V.A. RUSANOV

that even when using the relatively light crawler tractor I'-70C, which exceeds the permissible ground pressure of 80 kPa by 100%, reduction in yield of sugar beet roots averaged 2.8% ( 1.7 t ha- ~ ). The MTZ-52 wheel tractor and the DT-75M crawler Uactor with ground pressures exceeding the permissible value by 174 and 200%, respectively, caused 5.1-6.1% (3.1-3.6 t ha -~ ) reduction in sugar beet root yield. The smallest corn grain yield reduction ( 1.7%) was found when using the T-70C tractor with a ground pressure of 108 kPa, which is close !o the permissible value (80 kPa). The other tractors caused signifi- cant reductioas in corn grain yield of, on average for a 3-year period, 5.8- 8.9% (0.3-0.5 t ha- ~ ). In the experiments performed by the Ukrainian Ag- ricultural Academy on two soil types in the Ukraine, even larger reduction in the yields of sugar beet roots and of corn were registered (Gaponenko, 1971 ).

Numerous experiments have shown that exposure of soil to wheel and track traffic may change its cultivation characteristics, the change being larger the higher the actual pressure exerted on the soil (Rusanov et al., 1982). For example, when ploughing the trail of a crawler tractor T-150, the content of soil aggregates > 5 cm in diameter increased by 4% (w/w) as compared with the control (Fig. 3 ). However, in the case of the K-701 tractor this increase amounted to 31% (w/w). When ploughing the trail of the K-701 tractor, the proportion of soil clods > 25 cm in diameter was 15 times larger than when ploughing the trail of the T-150 tractor.

Compaction brings about increases in soil strength, soil adhesion and soil resistance to tillage (Rusanov et al., 1981 a). When ploughing soil compacted by the MTZ-type wheel tractors and by crawler tractors, the resistance to til- lage increases by 12-25%, by 44-65% when compacted by the T-150K and K-701 tractors, and by 60-90% in case of compaction of soil by trucks, com- bine harvesters and various trailers. Calculations demonstrate that, when cul- tivating cereal crops, fuel expenditures for treatment of compacted soil in- crease by 20-30% and more, with the same reduction in productivity of soil tillage units. When cultivating sugar beet fields after harvest, and trailers pulled by MTZ tractors were used to transport the produce from the fields, fuel ex- penditures increase even by over 50%. An increase in the number of passes over the same trail from one to three, brings about a two-fold increase in soil resistance to tillage. However, when the soil was subjected to traffic of vehi- cles with reduced ground pressure, the absolute value of soil resistance to til- lage remained lower in all cases.

CONCLUSIONS

The analysis of the effects of wheel and track traffic ca the soil indicates that, generally, modern heavy tillage and harvest equipment inflicts consid- erable damage on the soil, and reduces its actual and potential fertility. In the

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EFFECTS OF WHEEL AND TRACK TRAFFIC ON SOIL AND CROPS 143

U.S.S.R. , this e q u i p m e n t also has poo r opera t ing and main tenance character- istics, and does not mee t the r equ i rement s o f present -day agriculture, includ- ing the cr i ter ion o f s table agricultural farming.

It is necessary to deve lop a new or i m p r o v e d concept o f agricultural equip- ment , that wou ld take into accoun t not only the r equ i r emea t o f increased labour product iv i ty , bu t also the mos t impor t an t r equ i rement o f i m p r o v e d crop growth and yield o f such qual i ty that it wou ld enable the p roduc t ion o f food which is biologically compa t ib l e with the health o f man.

ACKNOWLEDGEMENT

Thanks are due to E.V. Chekhalov, who t rans la ted the original Russ ian text into English.

REFERENCES

Gaponenko, V.S., 1971. Compaction of soil by running gear of class 3 and 5 tractors at spring field work. Proc. Ukrain. Agric. Acad., Kiev, Vol. 34 (in Russian).

Kachinsky, N.A., 1927. Effect of tractor-powered tillage on physical properties of soil. Proc. State Soil Inst., Moscow, Vol. 1 (in Russian).

Makarets, I K., 1967. Effect of wheel .'factors on physical propert,.'es of soil. Tractors and Agri- cultural Machinery, No. 3 (in Russian).

Pigulevsky, M.H., 1929. Report on tractor tests in Persianovka. Part III, Leningrad (in Russian). Puponin, A.I., Matiuk, N.S., Rusanov, V.A., et al., 198 I. Deformation of sod-podzolic soil by

running gear of tractors and crop yield. Zemledelie, No. 6 (in Russian). Rusanov, V.A., Nebogin, I.S. and Fironov, N.N., 198 l a. Variation of power expenditures for

cultivation of soil compacted by various running gear systems. Trans. VIM, Vol. 91 (in Russian).

Rusanov, V.A., 1988. Basic regulations used in the elaboration of GOSTs of rates and technique of evaluation of effect of traffic on soil (GOST 26955-86, GOST 26953-86 and GOST 26954- 86). Collect. Pap. VIM, Vol. 118 (in Russian).

Rusanov, V.A., Bautin, V.M., Nebogin, I.S. and Jushkov, E.S., 198 lb. Effect of running gear of tractors on yields of intertilled crops. Trans. Soil Inst. after V.V. Dokuchaev, Impact of Ag- ricultural Machinery on Soil, Moscow (in Russian ).

Rusanov, V.A., Nebogin, I.S., P.chenko, I.R. and Fironov, N.N., 1982. Evaluation of effects of various traffic on change of soil characteristics. Trans. VIM, Vol. 92 (in Russian).

Rusanov, V.A., Sadovnikov, A.N., Jushkov, E.S, Bautin, V.M. and Nebogin, I.S., 1983. Effects of tractor traffic on soil and its fertility. Mechanization and Electrification of Agriculture, No. 5 (in Russian).

Rusanov, V.A., Nebogin, I.S., Bautin, V.M. and Juskov, E.S., 1989. Variation of density, strength and fertility of Kuban black-earth under the impact of tractor traffic. VIM, Sci. Technol. Bull. Vol. 75 (in Russian).

VIM, 1978. Programme and technique of complex research for the study of the effects of run- ning gear of agricultural tractors, combine harvesters and trailers on soil. All-Union Re- search Institute of Agricultural Mechanization (VIM), Moscow (in Russian ).