China Southern Red Soil Erosion Of ~ (137) Cs Tracer Study

Soil erosion and sedimentation may not only cause on-site degradation of the natural resource base, but also off-site problems—downstream sediment deposition in fields, floodplains and water bodies, water pollution, eutrophication and reservoir siltation, etc.—with serious environmental and economic impairment. The vulnerable ecological region of red soil is one of the best agricultural resources potential in China. But this region is developed by seriously degraded red soil with complex landforms, many types of soil use and great intensity of agricultural production in China.The purpose of this research is to evaluate the suitability of the ¹³⁷Cs technique for estimating medium-term soil erosion rates at three sites under different land use in Jiangxi province, Southern China. A total 280 samples were collected to estimate soil redistribution rates on the basis of the ¹³⁷Cs inventories in soil samples collected at the four study sites. A representative fraction of each sample was placed in a plastic container for determination of ¹³⁷Cs activity by gamma spectrometry at 662 keV using a high-resolution coaxial HPGe detector with 62% relative efficiency coupled to a PC-based data collection system. Count times were typically 8h providing an analytical precision of 10% at the 95% level of confidence.Caesium-137 measurements were converted to soil erosion rates using the Mass Balance Model described in details by Yang et al., (1998) appropriate for cultivated land and the soil profile distribution model for uncultivated land. Medium-term soil erosion rates for the three sampling sites were estimated at: land covered with masson pines and lichen (3700kg/hm² a); dry farmland (83.1 kg/hm² a); paddy fields with terraces (79.2 kg/hm² a); woodlands with plough (1512 kg/hm².a), and 20 a economical woodlands (1249 kg/hm².a). These results suggested that the paddy field with no best management practices and conventional tillage was characterized by medium-term soil loss rates two-four times higher than those observed on the woodlands. Terraces, which were installed as conservation measures, had demonstrable effects on controlling soil erosion. Land covered with masson pines and lichen need additional soil conversation measurements. Slope plays an important role in affecting soil erosion rates on dry farmland. Economical woodlands have a positive effect on soil conservation in red soil, but another measurement is needed. Overall, the ¹³⁷Cs technique provides a reliable method for discrimination between soil redistribution rates on agricultural land under different land use and management in Southern China.