EFFECTS OF CRUST DEVELOPMENT AND SURFACE SLOPE ON EROSION BY RAINFALL

Erosion losses were determined when simulated rainfall (50 mm h-1) was applied to 1 m x 1 m field plots on three soils (Rhodoxeralf, Calciorthid, Natrixeralf) having surface slopes of 1-2%, 4-5%, and 7-8%. Low soil loss and high runoff volumes from the Rhodoxeralf were related to the rainfall-induced development of low hydraulic conductivity (K) and low macroporosity in the 0-2 mm-soil layer. Higher soil loss and lower runoff rates noted for the Calciorthid and the Natrixeralf were associated with higher K and macroporosity values for the surface soil. Soil loss from the Calciorthid, which had 29% coarse sand and 48% fine sand, increased markedly as the surface slope increased to 4-5% and 7-8%.