The effects of soil organic matter content, rainfall duration and aggregate size on soil detachment

Abstract

Soil detachment was measured using a factorial experiment involving five soils (with organic matter contents ranging from 1.23 to 5.64%), three rainfall durations (4, 12 and 20 mins) and two aggregate sizes (<2 mm and 2–5 mm). Detachment was described in terms of the direct effects and the first and second order interactions of these variables above. There were significant differences (P < 0.01) in the amount of soil detached between the study soils. The mean values of detachment generally declined with increasing soil organic matter content from 1.15 kg m −2 in the G1 soil to 0.51 kg m −2 in the G5 soil. For each soil, there were significant increases (P < 0.01) in detachment with increasing rainfall duration. Soil detachment was smaller for the larger aggregate size. The most significant interactions affecting soil detachment were between rainfall duration and aggregate size, organic matter content and aggregate size, and between organic content and rainfall duration in that order. These interactions were used to make inferences on the effect of organic matter on soil detachment. For each soil and aggregate size, power relationships were established to relate detachment to rainfall total kinetic energy and organic matter content.