Laboratory experiments on the effects of antecedent moisture content and residue application on structural properties of a fragile soil

Abstract

In model experiments, saturated hydraulic conductivity ( K s) of a fragile Miles fine sandy loam soil dried at 35°C was increased by incorporating sorghum residue, but decreased by increasing antecedent moisture. After 4 drying cycles at 35°C, the K s of soil with no residue ranged from 0.002 cm h −1 when antecedent moisture was high to 1.4 cm h −1 when antecedent moisture was very low. The K s of soil with high residue ranged from 0.4 cm h −1 when antecedent moisture was high to 11.2 cm h −1 when antecedent moisture was low. The K s of slow-dried soil at 25°C, unlike fast dried soil, increased with increasing moisture. Slow-drying at 25°C or under a straw much increased natural compaction and reduced K s of soils. Finally, the K s of soils was a function of drying conditions, straw management, antecedent moisture and their interactions. These results indicate that slow-drying and increased moisture created by conservation or reduced-tillage systems can increase natural compaction and decrease permeability of some soils.