Soil loss estimation on a local scale for soil conservation planning

Abstract

A soil loss estimation of crop fields on a local scale was carried out using the Universal Soil Loss Equation (USLE) and Geographic Information System (GIS) tools. The study site covering 3,009 ha in Kanto, Japan, comprised 11,544 crop fields. The USLE provided an estimate of average annual soil loss based on the following factors: rainfall and runoff (R); soil erodibility (K); topography (LS); crop and management (C); and support practice (P). The dataset of the factors for each field was derived from available land information and field surveys. The K factor was estimated from the sediment yield in the small catchment area. The slope length and steepness of each field, required to compute the LS factor, were derived from field boundary information and a digital elevation model (DEM) constructed using GIS tools. The estimated soil loss rate under the current cropping conditions was found to range from 0.2 to 70.6 t ha-1 y-1, averaging 10.5 t ha-1 y-1. A distribution map of the rate indicated the fields where conservation measures should be taken. The study suggested that combining the USLE with GIS tools was likely to be useful for estimating soil loss on a local scale for soil conservation planning.