Stability of Agricultural Ecosystems: Validation of a Simple Model for Soil Erosion Assessment

Morgan, R.P. & Finney, H.J. (1982). Stability of Agricultural Ecosystems: Validation of a Simple Model for Soil Erosion Assessment. IIASA Collaborative Paper. IIASA, Laxenburg, Austria: CP-82-076

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Abstract

Validation trials of the model described by Morgan, Morgan and Finney (1982) for assessing the stability of the soil erosion component of an agricultural ecosystem were carried out using data from published studies of soil loss for 67 sites in 12 countries. Correlation coefficients of 0.74 and 0.58 were obtained between predicted and observed values of runoff at 56 sites and soil loss at 67 sites respectively. If two poor predictions of very high erosion rates in China are omitted, the value of the correlation coefficient for soil loss rises to 0.67 and the slope of the reduced major axis regression line is not significantly different from unity. The success of the model was also evaluated against the criteria that it should predict whether or not there was likely to be an erosion problem and if there was, that it should predict the magnitude of the problem. Against these criteria, the model was successful on 59 per cent of the tests for runoff and 70 percent of the tests for soil loss. Considering only those sites for which high quality input data were available, the success rate for soil loss rose to 90 per cent. Guidelines are presented for the selection of parameter values for rainfall intensity, weathering rates, soil renewal rates and rooting depth.

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