Productivity impact of soil erosion on the Loess Plateau - A modeling approach

Soil erosion and land degradation are severe problems on the Loess Plateau of China. The major on-site impact of erosion is the loss of soil productivity, but quantitative assessments are few. This paper, by using a modelling approach, addresses the issues of (i) erosion - productivity - time relationships and (ii) the effects of soil conditions and management practices. Under different scenarios of slope gradient, initial soil organic matter (OM) content and OM input levels, variations in biomass yield of a continuous winter wheat cropping system are simulated over a 100;year period. With erosion, the equilibrial biomass yield is predicted to be 720 to 940 kg/ha. The time to reach equilibrium, expressed as productive life, varies with erosion rate, initial soil productivity and management. On 47% slope with low OM input, the predicted productive life is 89 and 128 years for soils with initial low and high organic matter. Increasing OM input prolongs soil productive life, but this is largely offset by the effect of erosion on steep slopes. Soil productive halflife (the time taken for a soil to lose 50% of its production potential) is 136 years longer in a high OM input system than in a low OM input system for a soil with initial OM content of 2.0% on 9% slope. However, on 47% slope, with high OM input, soil productive halflife can only be prolonged by 18 years.