Aggregate Breakdown and Soil Surface Sealing under Rainfall

Aggregate breakdown is an important process controlling the availability of fine soil material necessary for structural sealing of soil surfaces under rainfall. It may be caused by slaking resulting from rapid soil wetting and by physical dispersion resulting from direct and indirect energetic raindrop impacts. Relationships have been proposed by others predicting steady infiltration rate and saturated hydraulic conductivity from final aggregate size following high energy rainfall on initially dry, uncovered soil surfaces. Under these extreme conditions, both rapid wetting and energetic raindrop impact result in maximum aggregate breakdown and surface sealing. ¶ This study has isolated and quantified effects of rapid soil wetting and energetic raindrop impact on aggregate breakdown and surface sealing. Simulated rainfall was applied to re-packed soils from differing tillage treatments on light textured soils from near Cowra and Condobolin in New South Wales, Australia. ..