Conservation Reserve Program (CRP) areas that are returned to crop production will initially be much less erodible than fields which were farmed using conventional practices. In this study, a rainfall simulator was used to measure runoff anderosion from former CRP areas in Mississippi, Nebraska and South Dakota over approximately a two year period. Soil loss rates measured immediately following tillage on each of the three sites were similar to values obtained on the undisturbed CRPtreatments. However, when left in a fallow condition, the erosion-reducing effectiveness of the sod appeared to have lasted less than one year. The rapid increase in soil erodibility following tillage was attributed to a reduction in surface cover andorganic material. The WEPP and RUSLE models are currently used extensively in conservation planning and assessment. The experimental data collected in this study were used to derive selected parameter values for use in these models.
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