三峡库区紫色土坡地土壤退化特征:土壤养分贫瘠化

Characteristics of Soil Degradation of Purple Soil Sloping Field in the Three Gorges Reservoir Area:Impoverishment of Soil Nutrient

土壤侵蚀是三峡库区紫色土坡地土壤退化及土壤养分贫瘠化的主因。利用土地特性系列比较法，通过野外调查和室内分析相结合，研究三峡库区紫色土坡地土壤退化特征。结果表明：1）与未退化样地相比，不同利用方式和不同坡度段土壤中各种营养元素的含量均不同程度地减损。2）不同利用方式下土壤有机质、全N和碱解N含量由高到低是林地、园地、菜地（或草地）、耕地（或荒地）、建设用地。园地土壤中的全P、速效P、全K、速效K、CEC以及Fe、Zn、Ti、Pb等微量元素的含量均较高；草地土壤中的全K、速效K、CEC及微量元素含量一般较低；荒地土壤中各种营养元素的含量与草地基本类同，但Zr和Cr平均含量最高；建设用地中CEC含量最高；菜地土壤中Pb的平均含量最高，达29．85mg／kg。3）不同坡度段土壤各种养分平均含量差异不大，但速效P在10°～20°和大于30°坡度段、CEC在20°～30°和大于30°坡度段均有显著差异。Cu、Fe、Ni、Mo、Co、V6种微量元素易随土壤侵蚀或其他途径迁移。

Soil erosion is a main factor of soil degradation of purple soil sloping field in the Three Gorges reservoir area, and therefore it leads to impoverishment of soil nutrient. The purpose of this study is to investigate and test the characteristics of soil degradation on sloping field of purple soil located in the Three Gorges reservoir area by comparing a series of soil characters. The results show that： 1） Comparing with the samples without degradation, all kinds of nutrition dements of purple soil under different land use types and different slope segments have obviously derogated in different degree. 2） The content order of organic matter, total N and rapidly available N of different soil from high to low is： woodland, garden plot, vegetable plot （or grassplot）, plantation （or wasteland）, building land. There are higher contents of total P, rapidly available P, total K, rapidly available K, CEC and Fe, Zn, Ti, Pb, etc in garden plot, but lower contents of total K, rapidly available K, CEC and trace elements in grassplot. All kinds of nutrition dement contents of wasteland are similar with grassplot, but the highest contents of Zr and Cr. There are the highest contests of CEC and Pb respectively in building land and vegetable plot. 3） The average nutrient contents differ little but there are obvious difference of rapidly available P content between slope segments 10°-20°and 〉30°and CEC between slope segments of 20°-30°and 〉30°. The six kinds of trace elements such as Cu,Fe,Ni,Mo,Co,V easily transfer along with soil erosion and other approaches.