CESIUM-137 ESTIMATES OF SEDIMENT REDISTRIBUTION BY WIND

Redistribution of the fallout radio-nuclide cesium-137 was used to estimate net sediment redistribution on five near-level (slopes <2%) cultivated fields. Net sediment outputs averaged over the past 30 years were 0.8, 3.4, 6.1, 35.9, and 38.2 tons.ha-1.year-1. Wind was assumed to be the major transporting agent, since slopes were below the critical angle (4 to 5%) for water erosion by rilling. Critical erosion values of 1.0, 5.0, and 11.0 tons.ha-1.year-1 were exceeded on 77%, 71%, and 57% of all sites sampled, respectively. Accelerated erosion rates were significantly greater in the sandy loam and loam soils than in the silt loam soils. This was attributed to a greater percentage of readily erodible saltation-sized sediment and the reduced surface roughness elements. Topographical parameters and soil properties were generally poorly correlated with net sediment redistribution within the various fields, and the reasons for this are discussed.