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LSP Report LS7012

Improving the Degraded Structure of Fine Textured Soils
with Deep Tillage and Grass and Legume crops


Researchers: Claude Weil, ACAFT, Principal Researcher. Cooperating with McGill University, Montreal; Agriculture Canada, Ottawa; Silsoe College, Bedford, Great Britain; and OCFMFPT, Chatham

Funding: $95,740


  1. To reduce the level of compaction of fine textured soils using a subsoiling implement in order to improve crop yields.
  2. To measure the effects of soil compaction on crop growth and yield on a Bearbrook fine textured soil.
  3. To select a subsoiler implement in function of the depth and extent of the compaction observed.
  4. To evaluate the effectiveness of subsoiling in improving soil structure between depths of 20 cm to 60 cm. This is to be done for a range of soil moisture content above and below the plastic limit.
  5. To measure the moisture content at which Bearbrook soils are most susceptible to compaction. This is to be done using the proctor compaction test.
  6. To analyse the soil physical properties such as bulk density, soil structure, soil aggregate stability, total and drainable porosity in compacted vs. loosened soils.
  7. To present the results of this project in the form of guidelines on the use of subsoiling for fine textured soils.

Expected Benefits

  1. With a better understanding of the nature of the compaction observed in Bearbrook clays, OMAF staff will be in a position to advise farmers on the choice and proper use of subsoiler implements with respect to type, depth, timing and speed.

Summary of Research Results

The objective of this study was to evaluate the effectiveness of the Para-till subsoiler at restoring compacted soil. On the basis of soil physical measurements, there appears to be no advantage to this relatively expensive operation in a heavy swelling-shrinking clay since the subsoil appears to decompact itself by natural means. This conclusion is supported by the observations that the bulk density profiles of the subsoil shifted to a somewhat denser state after the compaction and seeding operations that all plots, including the compacted-only ones, reverted to their initial state or looser conditions after one winter and two crop seasons.

The yield analysis indicate in this short study period, the operations had few observable effects. By the second year, the alfalfa performed equally well in all treatments except that where the plots were compacted and subsoiled. Corn yields did not appear affected by any of the treatments. It is not, however, clear whether the low yield in the compacted-only plots was due to the compaction treatment or to damage to the drain lines (or perhaps another unknown cause).

The sampling methodology used for soil physical measurements, in particular for penetration resistance was clearly inadequate. A greater number of samples should have bene taken and the bulk density and moisture reading should be done in proximity to the penetrometer readings in order to provide a valid data base with which to normalize penetrometer data, which is necessary in order to drawn comparisons between treatments reading soil strength.

The methodology used does not allow any significant relationship to be drawn between the soil physical data and yields. However, the yield data in themselves indicate that subsoiling did nothing to help plant yields under the field conditions manifested during the time this study was in effect. Only through an adequate sampling strategy, a wider range of soil types, and a wider range of cropping systems and crop species can a realistic assessment of subsoiler action be made.




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Created: 03-23-1996
Last Revised: Tuesday, May 10, 2011 12:57:54 PM