Surface erosion assessment using 137Cs: examples from New Zealand

The 137Cs technique has provided the first quantitative, medium-term data on rates of soil redistribution by surface erosion on both cropland and rangeland in New Zealand. Use of the technique has demonstrated: high rates of soil redistribution by water erosion at two cropland sites under intensive vegetable production; a slow rate of net loss of soil by wind erosion associated with arable farming; a strong association between vegetation depletion and wind erosion on grazed rangeland. Research has also provided data on natural short-range variability of 137Cs in uneroded soils, and a technique for independently estimating 137Cs reference values from rainfall. The greatest research need remains the development of robust, accurate calibration procedures for converting 137Cs measurements to rates of erosion. (author)