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SWEEP Report #24

Investigation of Soil and Crop Response to Fall Subsoiling
in Southwestern Ontario

Researchers:
 
L. Leskiw, A. Laycock, Can-Ag Enterprises, Guelph, Ontario

Executive Summary

Evaluation Summary (Tech. Transfer Report Summaries)

View / Download Final Report [2045 KB pdf]

Associated SWEEP/LSP Research

 

 

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Completed: August, 1991

Key Words:

fall subsoiling, compaction, yields, Tye Paratill, B.C. Sub-mulcher, Strohm aerator, compaction measurement

Executive Summary

Subsoil compaction is considered to be a serious problem in southwestern Ontario. Based on inspections of seventy fields chosen at random, approximately 15% and 45% of the clay to clay loam soils in five Counties in the southwest were found to be severely and moderately affected, respectively (Can-Ag Enterprises Ltd., 1988). The same study found corresponding crop yield declines to be some 25% and 12.5%, based on farmers reported yields for the fields inspected.

In 1988 a group of farmers initiated subsoiling experiments to examine corn response to interrow subsoiling in mid-June. Can-Ag Enterprises Ltd. was contracted to monitor soil conditions and crop response. It was a very dry year and significant crop yield increases occurred on only two of the thirteen fields. These two fields had severely compacted soils: others were rated moderately compacted. A lack of response on moderately compacted soils was attributed to increased droughtiness following subsoiling and below average rainfall.

The current study commenced in fall 1989, involving fourteen different fields but not all of the same farmers. Its objective was to determine the impact of subsoiling to a depth of about 30 cm after wheat harvest on subsequent crop yields. Three subsoiling implements were used in the research: Tye Paratill Strohm aerator, and B.C. Sub-mulcher. Field length strips (0.5-1 km long and 10 or 20 metres in width), two replicates each, were established to monitor effectiveness of each implement and a control.

Soils in each strip were examined to determine the degree and characteristics of compaction shortly after subsoiling in 1989 and again after the 1990 harvest. Measurements included hand and cone penetrometer readings, soil bulk densities on control plots, and detailed visual inspections of structure and pores. At a few fields, bulk densities were determined on all treatments.

The 1990 crop yields were measured by the farmers. They harvested each strip separately and used weigh wagons to determine yields. Farmers also shared their experience with respect to workability of the soils, ponding following rains, and their evaluation of the degree of compaction. In addition, they monitored all inputs including field operations, type of equipment used, fertilizer and herbicide inputs, and general crop performance during the growing season.

Statistical analyses were conducted to determine significant differences in crop response and soil conditions to the treatments. Also a Pearson correlation matrix was used to identify significant correlations among various soil parameters, management inputs, and crop yields.

Results indicated significant changes in soil conditions to the different subsoilers, however, only two fields produced a substantial crop yield increase. Considering all plots as a group, there was not a significant yield response in 1990 to the fall 1989 subsoiling. Moisture conditions throughout the 1990 growing season were good, seldom being too wet or too dry. Soil compaction was rated moderate on eleven fields, slight to moderate on one, and moderate to severe on two. Twelve of the fields were clayey, specifically, clay loams, silty clays and silty clay loams. The other two were sandy loams.

The Paratill was the most effective implement in reducing soil compaction and soil differences remained visible and measurable in the fall 1990. The Strohm aerator appeared to be slightly, but not significantly, more effective than the B.C. Sub-mulcher.

Measurements of fuel consumption per hectare indicated highest requirements for the Strohm aerator followed by the Paratill, and then the B.C. Sub-mulcher. The Paratill required the highest draught followed by the Strohm aerator and the B.C. Sub-mulcher. This apparent anomaly is possibly due to malfunctioning draught pins in the computerized tractor providing questionable numbers. The lack of any wings on the shanks of the B.C. Sub-mulcher makes it easiest to pull even though it had more shanks and was wider than the other subsoilers.

Examination of management inputs complicates interpretation of the results. Four farmers fall plowed their fields in 1989 (after subsoiling) as deep as they were subsoiled. This was their normal practice, perhaps a substitute for subsoiling. One of these fields was moderate to severely compacted, while the others were moderately compacted, all being clayey soils. A lack of yield response on these fields may therefore be due to deep plowing eliminating the effects of subsoiling. Of the two fields where good yield responses in soybeans were measured on the Paratill treatments, on moderately compacted clayey soils, one was no-till and the other was conservation tillage. Correlation analyses indicated a positive relationship between yields and soil fertility levels.

A lack of more noticeable yield responses in 1990 may be due to the relatively favourable moisture conditions through the growing season, even though soil conditions appeared to benefit from subsoiling. Furthermore, the fact that most of the sites were moderately compacted made it difficult to relate responses of yield to degree of compaction.

In the literature, mixed responses to subsoiling were reported. Our studies indicated that compacted subsoils were widespread, however, crop responses to subsoiling have not been clearly predictable nor measurable. First, longer term studies are essential to encompass weather variability. To save costs, farmers should confine subsoiling to severely compacted sites until more is known about crop responses to subsoiling. Of the implements used, the Paratill is considered to be the most effective subsoiler, keeping in mind that this is based on one year of data from four fields. In the heavy clay soils, tillage practices such as deep plowing or chiselling are also considered effective in ameliorating compaction at the 15 to 30 cm depth. Farmers should also be aware of other management practices which tend to alleviate soil compaction. These include:

  • reduction in vehicle weights (axle loads),

  • avoiding working on wet or very moist soils,

  • limiting the number of passes over the field, especially if moist, and

  • utilizing cropping systems and rotations which facilitate the above and provide crops with deep rooting action as well as maintain or improve soil organic matter content.

On severely compacted soils subsoiling may be viable, however, farmers should establish trials first to determine whether there is a significant and economical yield response. Adoption of the above mentioned practices is also advised to reduce re-compaction of the soils likely to occur in one or two years.

Evaluation Summary

(From Technology Transfer Report Summaries - A. Hayes, L. Cruickshank, Co-Chairs)

This study examined the effect of fall subsoiling on the yield and response of the subsequent crop and soil structure. Three subsoilers were compared - the Tye Paratill, B.C. Sub-mulcher and the Strohm aerator. Fourteen fields in Kent County were subsoiled to a depth of approximately 30 cm in the fall of 1989 following soybean or winter wheat harvest. Field length strips (0.5-1 km long and 10 or 20 m wide), two replicates each, were established to monitor effectiveness of each implement and a control.

Soils in each strip were examined to determine the degree and characteristics of compaction shortly after subsoiling in 1989 and again after the 1990 harvest. Measurements included hand and cone penetrometer readings, soil bulk densities on control plots and detailed visual inspection of structure and pores.

The 1990 crop yields were measured by the farmers using weigh wagons. Farmers shared their experience with respect to workability of the soils, ponding, and their evaluation of degree of compaction. All inputs including field operations, fertilizer and herbicide inputs and general crop performance were recorded.

Soil compaction was rated moderate on eleven fields, slight to moderate on one and moderate to severe on two. Twelve of the fields were clayey (clay loams, silty clays and silty clay loams), the other two were sandy loams.

There were significant changes in soil conditions with the different subsoilers, however, only two fields showed a substantial yield increase. Overall, there was no significant yield response in 1990 to the 1989 subsoiling. Moisture conditions throughout the 1990 growing seasons were good, therefore the benefits of subsoil alleviation would not likely be evident.

The Paratill was the most effective implement in reducing soil compaction. The only residual effects seen in the fall of 1990 were on plots in conservation tillage. In 1989 after the subsoiling operation, four farmers fall plowed their fields as deep as they had been subsoiled. A lack of yield response on these fields may be due to the deep plowing (their normal practice).

Response to subsoiling has not been clearly measurable or predictable.

Comments:

This experiment was only one year in duration. Only two of the sites were determined to be more than moderately compacted. Response to subsoiling will depend on the severity of the compaction, soil moisture conditions at the time of subsoiling, depth of plowing and weather conditions in the growing season following fall subsoiling.

An interesting observation by the researchers was that farmers who were shallow plowing were more likely to have a compaction problem than those who were plowing to the bottom of the topsoil-subsoil interface.

Associated SWEEP/LSP Research:

  • SWEEP Report #4 - Assessment of Soil Compaction and Structural Degradation in the Lowland Clay Soils

  • SWEEP Report #16 - Effects of Subsoiling on Corn Yields and Soil Conditions in Southwestern Ontario

  • LSP 7002 - Management of Fine Textured Poorly Drained Soils for Intensive Agriculture

  • LSP 7006 / 7007 - Management of Fine Textured Poorly Drained Soils for Intensive Agriculture: Characterization of a Forage Factor - Parts I and II

  • LSP 7012 - Improving the Degraded Structure of Fine Textured Soils with Deep Tillage and Grass and Legume Crops

  • LSP 7013 - Improving the Degraded Structure of a Clay Loam Soil with Deep Tillage and Grass and Legume Crops

  • LSP 7015 - Crop Production with a No-Traffic Tillage System

Future Research: ( ) indicates reviewers suggestion for priority, A - high, C - low.

None required.

 

 

 

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Created: 05-28-1996
Last Revised: Thursday, May 19, 2011 02:22:24 PM