Tillage system effects on stability and sorptivity of soil aggregates

Abstract

Stability and sorptivity of soil aggregates play an important role in numerous soil processes and functions. They are largely influenced by tillage methods. We have compared the effects of long-term application of various tillage systems on ag- gregate bulk density, rate of wetting, sorptivity, water stability, tensile strength and bulk density of silt loam Eutric Fluvisol. Tillage treatments were: 1) ploughing to the depth of 20 cm (CT), 2) ploughing to 20 cm every 6 years and harrowing to 5 cm in the remaining years (S/CT), 3) harrowing to 5 cm each year (S), 4) so- wing to uncultivated soil (NT), all in a micro-plot experiment. Bulk density of soil aggregates was determined by wax method, sorptivity - by a steady state flow, water stability - by drop impact method, and tensile strength - by crushing test. Tillage had a signi- ficant effect on the aggregate characteristics. Soil aggregate bulk density and water stability were greater and rate of wetting and sorptivity were smaller in reduced and no-tillage treatments com- pared with CT. Greater soil organic matter and bulk density accom- panied greater water stability. Smaller rate of wetting and sorpti- vity can be associated with lower aggregate porosity. The differen- ces in the rate of wetting, sorptivity, and water stability of the initially air-dry soil aggregates and bulk density between the tillage treatments were relatively greater than those in the tensile strength.