Soil loss and soil conservation measures on steep sloping orchards

Heavy and concentrated rainfall, brittle rocks, unstable stratum, steep terrain, intricate land usage and management, as well as diversified cropping system makes soil erosion problems in Taiwan unique. In order to deal with soil loss and land degradation problems, Taiwan's first pilot soil conservation demonstration project was established in 1952. However, the increasing pressure on land resources makes the soil loss assessment on steep slopes more important than ever. On-site measurements on soil losses from 60%-steepness orchards were monitored for four consecutive years. The bare plot had the highest soil loss with an average of 365.2 tons/ha. Vegetation, grass strip, surface mulch, and hillside ditches were found to be effective on steep slopes. These conservation measures can greatly reduce soil losses and conserve surface runoff. By feeding the Universal Soil Loss Equation (USLE) with a local rainfall erosivity index and an estimated soil erodibility index, the estimated annual soil loss from a 60%-steepness bare slope was found to be 73 times higher than the actual average field measurements. Slope length and slope steep-ness factors are the variables most likely to over-estimate soil loss.