Soil mineralogy and texture effects on crust micromorphology, infiltration, and erosion

Soil mineralogy and texture have substantial effects on aggregate stability and, therefore, may influence infiltration rate (IR) and soil loss under rainfall. The objective was to study the effects of soil mineralogy and texture on crust micromorphology, infiltration, and erosion. Five soils with differing properties were subjected to 80 mm of simulated rainfall. The aggregate stability of these soils was determined by the fast wetting method. The mean-weight diameters of the particles after the fast wetting were 2.8 mm in the clayey kaolinitic soil, 0.25 and 0.31 mm in the clayey and sandy loam montmorillonitic soils, respectively, and 0.84 and 0.87 mm in the clayey nonphyllosilicate soils. The final IR was 20.5 mm h^-1 in the clayey kaolinitic soil and ≤9.3 mm h^-1 in the remaining soils. Scanning electron microscope (SEM) observations indicated that the kaolinitic soil had a thin crust (∼0.1 mm) containing large particles (∼0.1 mm), whereas the montmorillonitic soils had thicker crusts (>0.2 mm) comprising either small (∼0.02 mm) particles with a very developed washed-in zone underneath or large (∼0.2 mm) ones with fine material between them. The crust layer in the nonphyllosilicate soils was ∼0.2 mm thick and composed of fine particles ∼0.01 mm. The high aggregate stability and the low dispersivity of the kaolinitic soil, which minimized soil detachment, and its low runoff, which minimized its transport capacity, limited the soil loss to 0.33 kg m^-2, whereas the low aggregate stability and high runoff of the montmorillonitic soils contributed to their soil losses of 1.24 and 1.14 kg m^-2. The intermediate aggregate stability and the high runoff of the nonphyllosilicate soils accounted for their intermediate soil losses of 0.75 and 0.8 kg m^-2.