USE OF RADIOACTIVE FALLOUT CESIUM-137 TO ESTIMATE SOIL EROSION ON THREE FARMS IN WEST CENTRAL OHIO

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Abstract
Assessment of the impact of soil erosion on productivity and environment quality requires comprehensive and credible estimates of erosion. Measuring concentration of 137Cs fallout is a relatively simple and rapid technique for determining long-term mean annual rates of soil erosion and deposition. The purpose of this study was to evaluate the potential of the 137Cs activity-soil depth relationship in estimating soil erosion from arable land in west central Ohio. Thus, soil samples obtained from three to four genetic horizons of four erosion phases at three farms in Clark Co., Ohio, (hereafter called Sites A, B, and C) were analyzed for 137Cs activity. Relationships between 137Cs activity and soil depth at undisturbed reference sites were used to calculate the depth of soil eroded and mean annual erosion rates. Cumulative 137Cs activities ranged from 6.8 mBq g−1 for the severely eroded phase at Site C to 16.6 mBq g−1 for the deposition phase at Site A. These activities corresponded to soil erosion rates of 125.9 Mg ha−1 y−1 for severe to 26.6 Mg ha−1 y−1 for deposition phases. A general trend of increasing soil erosion (by 24 to 85%) from slightly to severely eroded phases was observed although the data were highly variable. Estimated soil erosion rates depended on the regression model used and were more than an order of magnitude higher than those determined using the Revised Universal Soil Loss Equation. Sampling rigorously at small depth increments by means of a core sampler, careful selection of reference sites, and calibration or validation of this technique with other models can improve estimation of soil erosion using 137Cs. The 137Cs technique is, however, limited to local scale estimates of erosion because the empirical models are site specific.