COMPACTABILITY IN RELATION TO TEXTURE AND ORGANIC MATTER CONTENT OF ALLUVIAL SOILS

There is growing realization that the green revolution technologies have, in general,
resulted in soil compaction and ultimately reduction in soil productivity. The
relationships between soil compactability and a range of soil textural classes and soil
organic matter contents were described. The maximum bulk density, critical water
content and susceptibility of soil to compaction were found to increase with increase
in fineness of soil texture. Sandy soils achieved maximum compaction at relatively
low moisture content. Sand was almost fully compacted in their natural state (94%)
while loam may be compacted to the extent of about 17%. Although the Proctor test
was unable to identify the exact maximum compaction of swelling soil (clay loam)
which may exist in the field but the bulk density of clay loam soil was found to have
increased by 37% upon compaction and subsequent drying. An increase in soil organic
matter was found to reduce the risk of soil compaction at given moisture content.
The clay loam soil was found more sensitive to compaction but the application of
organic matter found to reduce its susceptibility to compaction to a larger extent as
compared to other soils. The study indicated that soil texture specific tests would be
required to determine the correct organic matter level to achieve a target bulk density
to avoid the problem of compaction arising due to mechanized intensive agriculture.