Quantifying Soil Erosion Under Unobstructed Runoff Conditions of a 7.7 Ha Peanut-Cotton Cropping System.

The lack of true soil erosion field data, which is required for the verification and calibration of soil erosion models, has been one of the serious problems in the soil conservation modeling today. Observing soil erosion of a relatively large field under truly unobstructed runoff conditions has rarely been done before. Report here is the results of our observation of soil erosion in a 7.7 ha peanut-cotton cropping system in the Mears Farm of Grand Ridge, FL. We used the mesh-pad method to quantify soil loss from the field and soil redistribution in the field over the entire cropping season of 2010. The main slope (1-3 %) of the field is about 220 m long. The results show that 1) the amount of soil loss from the field is only a small fraction (0.6 % - 4.3 %) of the soil re-distribution in the field and 2) the amounts of soil loss predicted by a SWAT model is 10-20 times greater than the observed values. Soil erosion process is quite heterogeneous and complicated even on a seemingly uniform cultivated field. There are serious soil erosion models developed over the years. Those models need to be verified and calibrated by extensive true field data to improve their performance.