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
- To reduce the level of compaction of fine textured soils using
a subsoiling implement in order to improve crop yields.
- To measure the effects of soil compaction on crop growth and
yield on a Bearbrook fine textured soil.
- To select a subsoiler implement in function of the depth and
extent of the compaction observed.
- 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.
- To measure the moisture content at which Bearbrook soils are
most susceptible to compaction. This is to be done using the proctor
- To analyse the soil physical properties such as bulk density,
soil structure, soil aggregate stability, total and drainable porosity
in compacted vs. loosened soils.
- To present the results of this project in the form of guidelines
on the use of subsoiling for fine textured soils.
- 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.
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.
Tuesday, May 10, 2011 12:57:54 PM