Influence of high axle loads and tillage systems on soil properties and grain corn yield

Soil& Tillage Research, 29 (1994) 229-235 0167-1987/94/$07.00 © 1994 - Elsevier Science B.V. All rights reserved

229

Influence of high axle loads and tillage systems on soil properties and grain corn yield G.A. Stewart, T.J. Vyn* Department of Crop Science, Universityof Guelph, Guelph, Ont. N1G 2 WI, Canada

Abs~a~ The effects of various tillage systems in combination with different levels of high axle load traffic on soil bulk density, penetration resistance and corn (Zea mays L. ) grain yields were studied for a 3 year period on a silt loam soil. The tillage systems were zero tillage, fall chisel plowing and fall moldboard plowing. Traffic treatments involved the annual post-harvest imposition ofa 12 Mg axle weight on 100%, 25%, and 0% of the plot surface area. The 0% treatment involved controlling all field traffic with the use of a wide span tractor. Only in the third year were differences in soil bulk density resulting from loading significant within all three tillage systems at the 5-10 cm depth interval. At a depth of 20-25 cm (below the maximum depth of tillage) differences in soil bulk density resulting from loading were never significant regardless of the tillage system or year. Differences in penetrometer resistance in the 0-10 cm depth interval resulting from loading were generally only significant in zero tillage, but they were often significant within all tillage systems in the 12-22 cm depth interval. The maximum depth to which loading caused significant increases in penetrometer resistance was 35 cm. Corn grain yields were significantly higher for the traffic-free treatments within only one tillage system (moldboard) in only 1 year (1988) of the experiment. In general, axle loads of 12 Mg did not resul! in reduced grain corn yields regardless of whether they were imposed on 25% or 100% of the plol surface area.

Introduction Previous research into the effects of soil compaction (see reviews: Soane et al., 1982; Hhkansson et al., 1988) has outlined several areas of concern, including the effects of high axle loads on soil physical properties at depths below that of normal tillage. Coincident with the concerns over high axle loads and soil compaction have been the problems of soil erosion and the loss of soil organic matter and structural stability with many annual cropping programmes. To combat this soil degradation, tillage systems which tend to reduce the amount of soil disturbance and increase the levels of surface residue have been implemented to a considerable extent in North America. Tillage research in Ontario has generally found that soil bulk densities and *Corresponding author.

SSDI0167-1987(93)08013-C

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G.A. Stewart, T..L Vyn / Soil & Tillage Research 29 (1994)229-235

penetrometer resistances in the surface 20 cm were significantly higher with zero tillage than with conventional moldboard tillage (Vyn et al., 1982 ). Investigations into tillage practices and compaction by Voorhees (1983) concluded that natural weathering forces over the course of one winter had reduced penetrometer resistance in a compacted plow layer by 20-50%, but had little effect on soil bulk density. Within this same study, reduced forms of tillage such as chisel plow or tandem disk were only slightly more effective than natural forces alone in reducing compaction. Little research has been done on the effect of reduced tillage systems on subsoil compaction caused by high axle load wheel traffic in Ontario. This study was conducted to determine the main and interactive effects of various high axle load traffic patterns and tillage systems on soil properties and corn productivity. Materials and methods

In the fall of 1986 we initiated a 3 year field study at Elora, Ontario, Canada, on a London loam soil (Typic Hapludoll) with 170 g kg -~ sand, 590 g kg- ~silt and 240 g kg- ~clay in the upper 20 cm. Soil organic matter averaged 38 g kg-~ in the upper 10 cm of the soil profile. Standard Proctor test indicated a maximum density of 1.63 Mg m -3 at a soil moisture of 0.195 g gfor the upper 20 cm of the soil profile and a maximum bulk density of 1.86 Mg m-3 at a moisture content of0.142 g g-~ for the 20-40 cm depth interval. Corn had been grown continuously with conventional (moldboard) tillage and with annual manure applications for the previous 7 years. A split plot design was used. The main plots were ( 1 ) zero tillage, (2) chisel plowing ( 18 cm depth) in the fall followed by secondary tillage in the spring, and (3) moldboard plowing ( 18 cm depth) in the fall followed by secondary tillage in the spring. There were three subtreatments: ( 1 ) 100% tracked area-a large self-propelled combine with its grain bin filled to capacity (combine front axle load was approximately 12 Mg on tyres 78 cm wide inflated to 145 kPa) was tracked through the plot (prior to fall tillage) on a wheel-track to wheel-track basis covering 100% of the plot surface area; (2) 25% tracked area--the same combine as in ( 1 ) was tracked through the plot (prior to fall tillage) to cover 25% of the plot surface area, the combine being tracked over the same pattern once in 1986 and twice in both 1987 and 1988; (3) 0% tracked area--no high axle load was imposed and field operations were performed with the use of a wide span tractor (Field Power Unit, Ashot AshkeIon Industries, Ashkelon, Israel) which had a wheel base wide enough to straddle the plots thus eliminating virtually all wheel traffic. Each year all plots received traffic from a small plot combine (axle load less than 4 Mg). For Subtreatments 1 and 2 all other field operations were performed using

G.A. Stewart, 7~J. Vyn / Soil & Tillage Research 29 (1994) 229-235

2 31

conventional machinery with axle loads of less than 5 Mg. Single subplot dimensions were 6.1 m X 30.5 m and all treatments were replicated four times. Following harvest, loads and tillage systems were imposed on the same plots during each of the 3 experimental years. Loading was done each fall when the soil profile (0-45 cm) was uniformly wet (slightly less than field capacity ); however, the ruts formed by the tyres were never deeper than 2-3 cm (depth of the tyre lug). All plots were planted each year in early May to corn in rows 76 cm apart at a population of 73 800 plants h a - 1 Undisturbed soil cores (4.7 c m X 5 . 0 cm) were taken each year following planting at three locations per plot and at two depths (5-10 cm and 20-25 cm ) per location. These cores were used to determine macroporosity by equilibrating them at matric tensions of 0.01 and 0.033 MPa. Following pore size characterization, soil was removed from the cores and dried to determine bulk density. Penetrometer resistance measurements were made in July of 1987 and in June of 1988 and 1989 using a hand-held recording penetrometer (Rimik, Toowoomba, Australia) taking a m i n i m u m of 12 probes per plot to a depth of 45 cm. Cone resistance was measured in 1.5 cm depth increments. Stainless steel rods were inserted to depths of 15, 30 and 45 cm and used to measure volumetric soil moisture with the time domain reflectometry method (Topp et al., 1984) throughout the growing season. Soil moisture measurements were taken in order to assess moisture differences among treatments at the time of penetrometer resistance readings. In general soil property measurements were made only on the 0% and 100% subtreatments and never in wheel tracks formed by spring field operations. Corn plant dry matter accumulation was measured at various stages of development by performing whole plant harvests. Final grain yield was determined by hand harvesting 20 m of row per plot. In 1988 and 1989, separate plant measurements were taken both in and out of the high axle wheel track zone in the 25% load subtreatment. This paper will only discuss the effects of treatments on soil bulk density, soil penetrometer resistance and corn grain yields. Results

Differences in dry bulk density at the 5-10 cm depth interval among the treatments as measured shortly after planting are outlined in Table 1. At this depth interval, significant differences existed among the main tillage treatments in each year. Differences in soil density at the 5-10 cm depth resulting from axle loading became increasingly more significant as the treatments were applied to the same plots during the 3 experimental years. The relative impact of the high axle load appeared to be similar within all three of the tillage systems at the shallow depth. At the 20-25 cm depth soil density was not significantly affected by the

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Table 1 T h e effects o f tillage a n d traffic t r e a t m e n t s on bulk d e n s i t y after planting corn Tillage a n d compaction treatment

Zero 0% track 100% track Chisel 0% track 100% track Moldboard 0% track 100% track

Bulk d e n s i t y ( M g m - 3 ) 5 - 1 0 c m d e p t h interval

2 0 - 2 5 c m d e p t h interval

1987

1988

1989

1987

1988

1989

area area

1.54 a 1.58 a

1.54 a 1.62 a

1.54 a 1.61 b

1.57 a 1.56 a

1.57 a 1.60 a

1.55 a 1.66 a

area area

1.37 a 1.32 a

1.26 a 1.35 b

1.30 a 1.39 b

1.55 a 1.57 a

1.58 a 1.58 a

1.59 a 1.55 a

area area

1.28 a 1.25 a

1.23 a 1.30 a

1.29 a 1.35 b

1.48 a 1.46 a

1.49 a 1.58 a

1.48 a 1.55 a

W i t h i n a m a i n t r e a t m e n t , axle loading s u b t r e a t m e n t s are n o t significantly different ( P < 0.05 ) w h e n followed by the s a m e letter.

high axle load regardless of the tillage system or of the year. At this depth, the moldboard tillage main treatment resulted in bulk densities which were significantly lower ( P < 0.05 ) than the zero tillage main treatment in both 1987 and 1989. Penetrometer resistance measurements taken during the growing season in each of the experimental years resulted in soil strength patterns similar to the one illustrated in Fig. 1. The principal tillage by traffic interaction existed at the 0-10 cm depth range where the differences between the loading subtreatments were only significant within zero tillage. From 12 cm to 22.5 cm in depth, the differences in penetrometer resistance between the loading subtreatments were significant within all three tillage systems. Throughout the experiment, significant differences in penetrometer resistance between 0% and 100% load were restricted to depths of less than 35 cm in any of the tillage systems. Penetrometer resistance values were frequently higher for zero tillage than for the other tillage systems even at depths below that of annual tillage. Differences in soil moisture recorded at the time ofpenetrometer measurements were generally not significant ( P < 0.05) and penetrometer readings were not adjusted. However, moisture levels in the compacted subtreatments were generally higher than the uncompacted subtreatments; hence, differences in actual soil strength between the two loading treatments were at least as great or perhaps greater than the penetrometer measurements indicated. Some differences did exist in soil moisture content during penetrometer readings between seasons and this precluded any strict comparison of penetrometer resistance values across years.

G.A. Stewart, T.J. Vyn ~Soil& Tillage Research 29 (1994) 229-235 PENETROMETER

RESISTANCE

1.0

2.0

0 3

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ZERO 0%

CHISEL 0%

MOLDBOARD 0%

ZERO 100% .................

CHISEL 1007"

MOLDBOARD

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1007. . . . .

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Fig. 1. T h e effects o f traffic a n d tillage o n p e n e t r o m e t e r r e s i s t a n c e in J u n e 1988. * D i f f e r e n c e s b e t w e e n l o a d i n g s u b t r e a t m e n t s w i t h i n a m a i n tillage t r e a t m e n t a r e s i g n i f i c a n t ( P < 0.05 ). Table 2 T h e effect o f tillage a n d traffic t r e a t m e n t s on final corn grain yields Tillage a n d compaction treatment

G r a i n yield ( M g ha - I ) 1987 a

1988

1989 a

Zero 0°/0 track area 25% track area 100% track area

9.01 a 8.26 a 8.25 a

6.24 a 5.27 b 6.06 a

6.00 a 6.18 a 6.56 a

Mean

8.51j

5.85j

6.25j

Chisel 0% track area 25% track area 100% track area

9.18 a 8.52 a 8.71 a

6.40 a 6.80 a 7.10a

6.56 a 7.27 a 7.56a

Mean

8.80j

6.84k

7.13j

Moldboard 0% track area 25% track area 100% track area

9.09 a 8.59 a 8.95a

7.66 a 7.15 b 7.11b

6.52 a 7.26 a 7.13a

Mean

8.88j

7.35 k

6.97j

aCorn yields in 1987 a n d 1989 were a d j u s t e d by covariance for corn population differences. Axle loading s u b t r e a t m e n t s ( w i t h i n a m a i n t r e a t m e n t ) or m a i n t r e a t m e n t m e a n s are not significantly different (P_< 0.05 ) w h e n followed by t h e s a m e letter.

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G.A. Stewart, T.J. Vyn /Soil & Tillage Research 29 (1994) 229-235

At harvest, differences in corn grain and total dry matter yields were generally not significant among the various axle loading treatments (Table 2). Only in 1988 and only within moldboard tillage was there a significant advantage in terms of grain yield for the 0% load over the 100% load subtreatment. The 25% load subtreatment generally gave yields intermediate to and not significantly different from the other loading treatments. Discussion and conclusions

In this study, soil below the maximum depth of tillage had significantly higher penetrometer resistances following the imposition of a 12 Mg axle weight. Bulk densities were not significantly altered at this same depth. These findings generally agree with Voorhees et al. ( 1978 ) who found penetrometer resistance to be more sensitive than bulk density when measuring the effects of wheel traffic on the soil. These results indicated that the 12 Mg axle load had no significant effect on soil properties below the 35 cm depth, while Hammel (1988), Gameda et al. (1985) and HLkansson (1985) reported effects down to depths of 75 cm, 60 cm and 50 cm, respectively, when imposing similar axle weights under various soil conditions. Corn grain yields were generally not reduced by the higher penetrometer resistance and densities in the 0-35 cm depth interval associated with the high axle load subtreatments. The lack of a positive response in terms of corn yield to the lower soil densities and penetrometer resistance found under the 0% load subtreatments may have been partially a result of reduced seedbed soil moisture (Stewart and Vyn, unpublished data). Precipitation in the month of May was 44%, 42% and 102% of normal while in July it was 130%, 101% and 9% of normal for 1987, 1988 and 1989, respectively. Periods of drought may have accentuated soil moisture stress in the uncompacted plots. However, precipitation for the entire May to July period was 106%, 70% and 101% of normal for 1987, 1988 and 1989 respectively, indicating that our results are not restricted to conditions of extremely low rainfall. Differences in bulk density and penetrometer resistance between moldboard and zero tillage below the tillage depth occurred frequently. Pidgeon and Soane ( 1977 ) reported similar findings in their tillage research. In Ontario, more extensive frost action on the moldboard plots may be part of the explanation. Kay et al. ( 1985 ) demonstrated that on a similar soil type under Ontario climatic conditions frost depth and activity were greater within a moldboard system than within a zero tillage system. However, they also concluded that reductions in bulk density which occur during freezing are unstable and that generally soils collapse to pre-frost densities upon thawing and drainage. We can only speculate that under the conditions in this study there may have been some residual effect of frost in lowering bulk densities, and more particularily in reducing penetrometer resistance, below the depth of

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235

tillage that occurred to a lesser extent under zero tillage than under chisel or moldboard tillage. In addition, contribution to the total resistance value which came by way of friction on the penetrometer shaft may have been higher for the zero tillage situation. Despite significantly lowering penetrometer resistance, the elimination of traffic from a zero tillage system did not overcome the 10-15% yield differential often incurred by zero tillage compared with conventional tillage for corn grown following corn. An axle weight typical of what might frequently occur at harvest, imposed prior to fall tillage without significant rutting, did not significantly reduce the following season's corn productivity on this soil type. However, changes in soil properties were observed often at depths that are normally unaffected by tillage operations. Because these property changes may persist and accumulate if traffic is repeated, future crop productivity may still be affected depending on the prevailing crop species and/or climatic conditions.

References Gameda, S., Raghavan, G.S.V., Theriault, R. and McKyes, E., 1985. High axle load compaction and corn yield. Trans. ASAE, 28:1759-1765. Hhkansson, I., 1985. Swedish experiments on subsoil compaction by vehicles with high axle load. Soil Use Manage., 1:113-116. Hhkansson, I., Voorhees, W.B. and Riley, H., 1988. Vehicle and wheel factors influencing soil compaction and crop response in different traffic regimes. Soil Tillage Res., 11: 239-282. Hammel, J.E., 1988. Influence of high axle loads on subsoil physical properties and crop yields in the Pacific Northwest, USA. In: B.D. Soane (Editor), Proceedings of the 11th Conference of the International Soil Tillage Research Organization (ISTRO), 11-15 July 1988 Edinburgh, Scotland, pp. 275-280. Kay, B.D., Grant, C.D. and Groenevelt, P.H., 1985. Significance of ground freezing on soil bulk density under zero tillage. Soil Sci. Soc. Am. J., 49: 973-978. Pidgeon, J.D. and Soane, B.D., 1977. Effects of tillage and direct drilling on soil during the growing season in a long-term barley mono-culture system. J. Agric. Sci., 88:431-442. Soane, B.D., Dickson, J.W. and Campbell, D.J., 1982. Compaction by agricultural vehicles: a review. III. Incidence and control of compaction in crop production. Soil Tillage Res., 2: 336. Topp, G.C., Davis, J.L., Bailey, W.G. and Zebchuk, W.D., 1984. The measurement of soil water content using a portable TDR hand probe. Can. J. Soil Sci., 64:313-321. Voorhees, W.B., 1983. Relative effectiveness of tillage and natural forces in alleviating wheel induced soil compaction. Soil Sci. Soc. Am. J., 47:129-133. Voorhees, W.B., Senst, C.G. and Nelson, W.W., 1978. Compaction and soil structure modification by wheel traffic in the northern corn belt. Soil Sci. Soc. Am. J., 42: 344-349. Vyn, T.J., Daynard, T.B. and Ketcheson, J.W., 1982. Effect of reduced tillage systems on soil physical properties and maize grain yield in Ontario. In: A Butorac (Editor), Proceedings of the 9th Conference of the International Soil Tillage Research Organization (ISTRO). 2227 June 1982 Osijek, Yugoslavia, pp. 27-32.