Variations of sediment nutrient in check dam and its implication for small catchment sediment resources

The sedimentological and nutritional characteristics of eroded soil particles from the Loess Plateau in China were investigated in this paper. The large number of check dams built in the Loess Plateau function, partly as the depositors of eroded soils, carries important information about the environemntal processes relating to soil erosion and deposition. In this study, the organic matter (OM) contents, total nitrogen (N) contents, total phosphorus (P) contents, and total potassium (K) contents in both deposits of the dams and in soil of different parts of the catchments were compared. The results showed that the variability of soil nutrients in the catchments was obviously larger than that in the dams; the variabilities of nutrients in the soils and in the gully walls were similar, where there was no significant difference between soil total N, total P, and total K in the gully walls and in sediments deposit profiles (p>0.05), but the soil nutrient contents were significantly lower than those on slope farmland and slope grassland (p<0.05). Those results implied that collapsing gully walls and expanding gullies were the main sources of sediments in check dams during the sediment trapping periods. The results also indicated that gravitational erosion and gully erosion were the two major erosion types in these small catchments. The variations of OM in the sediments and total N in the deposit profiles of the dams showed two different stages of development. It is concluded that sedimentological and nutritional differences result from the effects of the rural contract responsibility system on the land use and soil erosion.