Predicting soil erosion losses
1995
Kismosatmoro
The prediction of soil losses was based on the Universal Soil Loss Equation (USLE) using the results of 36 soil erosion studies consisting of 219 erosion plots in the Philippines (17 studies), Indonesia (15 studies) and Thailand (4 studies). Only plot results having significantly different means (165 plots) were used as database source. Using stepwise multiple regression, three model were studied. All models showed highly significant positive linear regression (R square greater than or equal to 0.98) using N=165. The relationship between predicted and actual soil losses showed positive linear relationship with correlation coefficient. The imposition of rainfall erosivity improved the relationships of predicted and actual soil loss, while imposition of the soil erodibility values slightly decreased the relationship. In the Philippines, based on type of climate, those values indicated medium to strong correlation (r = 0.43-0.99). Economic evaluation using plot data from 100 sq m and extrapolating to one hectare basis showed that all plots have positive Net Present Worth (NPW), Benefit Cost Ratio (BCR) greater than 1.0 ranging from 1.31 to 2.84, and Internal Rate of Return (IRR) was more than interest rate. High advantage of plots mostly originated from ecological benefits. Based on the analysis, biomass production and soil losses, the use of Panicum + Gliricidia hedgerows is the best choice for soil conservation. The modified USLE of original model was used to predict soil losses in the Pambukhan Watershed by employing a Geographic Information System. The original model of USLE may be used to predict soil erosion losses, to select land use and soil management considering a given rainfall, soil and topography, crop and current soil management of site and to formulate soil conservation practices
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