Response of changes in soil nutrients to soil erosion on a purple soil of cultivated sloping land

Severe soil erosion on cultivated sloping land in hilly areas of Sichuan has resulted in deterioration of soil quality,and therefore has an adverse impact on crop production.We selected a hillslope of 110 m in length with a slope steepness of 10.12% where the soils were classified as Regosols.Soil samples for the determination of 137Cs,soil organic matter(SOM),total N,P,K,available N,P,K and particle size fraction were collected at 10 m intervals along a transect of the hillslope.Effects of soil erosion on soil nutrient loss were studied by using 137Cs technique,and the relationships between 137Cs-derived soil redistribution rates and soil nutrients were established over the cultivated sloping land in hilly areas of Sichuan,China(30°26'N,104°28'E).SOM,total N,available N,P,K and the 0.002mm soil particle size fraction were smaller at upper and middle slope positions where lower 137Cs concentrations were present(i.e.soil erosion rates were greater) than at downslope positions where 137Cs concentrations were higher(i.e.soil erosion rates were less).The lowest 137Cs concentrations were found in the hilltop,showing that besides water erosion,tillage erosion also contributed to soil losses,and intensive tillage was mostly responsible for severe erosion at upper slope positions.There were significant differences in soil OM,total N,available N,P,K and the 0.002mm soil particle size fraction between different slope segments,and these properties were significantly correlated with slope length.These soil properties were also significantly correlated with 137Cs concentration,indicating that both 137Cs and nutrient concentrations varied with topographical changes.The variation in soil properties was strongly influenced by erosion-induced soil redistribution,and therefore 137Cs concentrations mirroring soil redistribution rates would be considered as an integrated indicator of soil quality.