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SWEEP Report #16

Effects of Subsoiling on Corn Yields and Soil Conditions
in Southwestern Ontario

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

Executive Summary

Evaluation Summary (Tech. Transfer Report Summaries)

View / Download Final Report  [1104 KB pdf]

Associated SWEEP/LSP Research



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Completed: September, 1990

Key Words:

post-emergence subsoiling, B.C. Sub-mulcher, corn, yields, compaction, inter-row subsoiling

Executive Summary

Twelve farmers from Kent County in southwestern Ontario co-operated in this study to observe the effect of subsoiling on corn yields and soil conditions.


This study focused on the subsoiler performance in the soil layer below the plow depth (i.e. about 15 to 30 cm below ground surface). This region within the soil profile is where compaction can occur. Soil compaction may include one or more of these conditions: degraded soil structure; reduced size, abundance and continuity of vertical cracks and pores; smearing; increased soil bulk density; layering; and, altered rooting pattern and depth. These conditions tend to reduce the soils' ability to produce abundant crops due to deterioration of root zone quality. Soil permeability is also reduced and this results in increased runoff and erosion.

A previous Can-Ag compaction study indicated that about 50 to 70 percent of the clay to clay loam soils in several southwestern Ontario counties are affected. Of this total, about 25% are severely compacted and 75% are moderately affected resulting in crop yield reduction, increased soil erosion, and increased phosphorus loadings to the Great Lakes.


The purpose of the study was to evaluate the B.C. Sub-mulcher, a narrow shank subsoiler, pulled through corn rows at depths of 18 and 31 cm in June of 1988. Not only did we look at the soil and plant response to the subsoiling, but also to determine what other management practices may affect soil compaction and yields.

Measurements of Compaction

Several methods are used to measure soil compaction and five of the more popular ways were used in this study: visual observations of a combination of factors, bulk density determinations, hand and cone penetrometer measurements and detailed descriptions of soil peds and pores (tubular and planar).

Statistical Analysis

The degree of compaction was assessed using two kinds of statistical analyses; a Pearson Correlation matrix and an analysis of variance. The ANOVA established differences among subsoiling treatments with respect to yields and measured soil properties. The Pearson Correlation matrix was made to examine correlations among various parameters measured and described.


The 1988 growing season lacked significant rainfall which contributed to below average yields. These abnormally dry conditions were excellent for the subsoiling operation but caused some yield loss in the subsoiling test strips.

Results indicate that shallow (18 cm) subsoiling was detrimental to yields: deeper subsoiling did not, on the average, have any effect. However, in the sites determined to be severely compacted, yields responded very favourably to deep subsoiling.

Subsoiling improved soil conditions, though these improvements were confined to a 20 cm width centred over the shank path.

An interesting management correlation showed an increase in yields with an increase in field operations, even though this has the potential to increase compaction. The dry season probably was the major factor for this observation. Since there was not any extensive periods of wet soil conditions during critical times for field operations, compaction associated with these operations did not occur. This points out the importance of proper timing of field operations in conjunction with soil conditions.


A few recommendations arising from this study concern the use of a post emergence subsoiler, especially in a dry year. These include:
  • pulling a packer behind the subsoiler to close the openings left by the subsoiler shanks to reduce moisture loss through evaporation;
  • the use of a subsoiler after wheat harvest where the soil is dry and there is no resulting moisture stress on a crop; and
  • further research on subsoiling timing and effects of implement design.


Evaluation Summary

(From Technology Transfer Report Summaries - A. Hayes, L. Cruickshank, Co-Chairs)
A one year subsoiling trial was conducted in June 1988 in corn at two depths, 18 cm and 31 cm using a B.C. Sub-mulcher in the Kent County area. Five different methods were used to assess soil compaction including visual observations, bulk density, hand and cone penetrometer measurements and detailed descriptions of soil peds and pores.

Soil conditions were dry at the time of subsoiling and continued dry for the remainder of the growing season. Shallow subsoiling (18 cm) reduced corn yields while deeper subsoiling did not, on average, have any effect. Two sites were determined to be severely compacted, yields did increase with the deep subsoiling. Soil conditions were improved in a 20 cm wide strip in the area of the shank path.


This study was limited to one season only. Other compaction studies would suggest that improvements in soil conditions as a result of subsoiling are normally short lived.

The effect of subsoiling is highly dependent on soil moisture conditions at the time of subsoiling and during the following growing season.

Associated SWEEP/LSP Research:

  • SWEEP Report #4 - Assessment of Soil Compaction and Structural Degradation in the Lowland Clay Soils
  • SWEEP Report #24 - Investigation of Soil and Crop Response to Fall Subsoiling in Southwestern Ontario
  • LSP 7002 - Management of Fine Textured Poorly Drained Soils for Intensive Agriculture
  • LSP 7006 & LSP 7007 - Management of Fine Textured Poorly Drained Soils For Intensive Agriculture: Characterization of a Forage Factor which Enhances the Growth of Corn in Rotation - 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 01:55:43 PM