Repair of the structure of a compacted Vertisol via wet/dry cycles

Abstract

The effect of wet/dry cycles on repairing a compacted Vertisol was studied. The change in soil structure was assessed by infiltration, clod bulk density, shear strength and image analysis of surface morphology. Wetting was done by flooding and by simulated rainfall. Drying was achieved by surface evaporation. Five flood-wet/dry cycles resulted in a two fold and one and a half fold increase in water infiltration rate for the wheel track and bed cores, respectively. This increase was associated with a marked decrease in surface shear strength of the cores after only one wet/dry cycle for both types of wetting. Quantification of the soil structure on the soil surface indicated that both % total crack and shrinkage block size decreased for wheel cores with the increasing number of wet/dry cycles. Cracks became narrower and size of shrinkage blocks smaller as the number of flood wet/dry cycles increased. Rain wetting produced bigger cracks and blocks but fewer in number compared with flood wetting. For flood-wet bed cores, higher values of clod specific volume after one flood-wet/dry cycle in the 0.05–0.2 m depth suggest that bulk density had decreased and porosity increased, relative to the original field condition.