Stability of microaggregates as influenced by antecedent moisture content, organic waste amendment and wetting and drying cycles

Abstract

A knowledge of some biophysical factors controlling the stability of microaggregates is important in understanding the mechanism involved in soil slaking, surface sealing, crusting, and erosion by water. A laboratory study was undertaken to evaluate the role of antecedent moisture content, cattle manure and wetting and drying cycles on the stability of microaggregates (<0.2 mm) of three texturally-contrasting soils from Lamporecchio, Vicarello and Cremona in northcentral Italy. In all experiments the order of microaggregate stability was Vicarello (clay) > Cremona (sandy-clay loam) > Lamporecchio (sandy loam) soils. This reflected decreasing clay contents and silica: alumina ratio. Maximum aggregation of particles <0.05 mm occurred at about −1.5 MPa moisture content in all soils. At the highest antecedent moisture content used (50%, w/w), the aggregation of the <0.05 mm particles was 2.77, 14.96 and 12.86% respectively for Lamporecchio, Vicarello and Cremona soils. In the Lamporecchio soil, aggregation of particles <0.05 mm increased with manure rate whereas in the Cremona and Vicarello soils, maximum aggregation of the <0.05 mm and <0.002 mm particles was obtained at the 2 and 6% rates respectively. The least disaggregation of particles <0.2 mm occurred at the 3 cycles of wetting and drying in all soils while maximum disaggregation was obtained at the 15 cycles.