柴达木盆地弃耕地成因及其土壤盐渍地球化学特征

柴达木盆地弃耕地土壤pH值一般都在 8左右 ,属于碱性土壤。土壤含盐量较高 ,其全盐量随着土层深度的增大而减少。 0～ 10cm土层中的含盐量最大 ,一般在 1～ 45gkg- 1之间。弃耕地土壤阳离子主要以K 、Na 、Mg2 、Ca2 为主 ,各阴离子在三层土体中的含量为Cl- >SO2 -4>HCO-3 >CO2 -3 。经相关分析表明 ,弃耕地土壤全盐量与Cl- 呈极显著的正相关 (p <0 0 1) ,其次为Mg2 和Ca2 (p <0 0 5) ,而与HCO-3 呈负相关 ;Cl- 与Mg2 和Ca2 呈极显著的正相关 (p <0 0 1) ,与CO2 -3 和SO2 -4呈弱的正相关 ,而与HCO-3 呈负相关 ;从而进一步说明 ,柴达木盆地弃耕地土壤为氯化物盐化土。柴达木盆地弃耕地土壤中有机质含量较少 ,0～ 3 0cm土层中有机质平均含量为 11 46gkg- 1;全氮、全磷的含量极低 ,全钾的含量较为丰富。示范试验结果分析认为 ,柴达木盆地荒漠绿洲土地退化及土壤盐碱化的发生与当地自然条件和人为不合理利用等因素有紧密的联系

FORMING FACTORS AND SALINE-GEOCHEMICAL FEATURES OF DESERTED FARMLAND IN QAIDAM BASIN

Deserted farmlands in the Qaidam Basin are mostly of alkali soil with pH value around 8,high in salt content. Salts concentrate mostly in the 0~10 cm surface layer,ranging within 1~45 g kg^-1,and decrease in content with depth of the profile.Cations in the soil are dominated with K⁺,Na⁺,Mg²⁺ and Ca²⁺,whereas anions are in a decreasing order of Cl^- > SO₄^2- > HCO₃^- > CO₃^2- in terms of content in the 0~10 cm,10~20 cm and 20~30 cm soil layers.The correlation between total salt and Cl^-content is positive and extremely significant(p<0.01),and that between total salt and Mg²⁺,Ca²⁺ content significantly positive,too(p<0.05),but that between total salt and HCO₃^- content negative,whereas,the correlation between Cl^- and Mg²⁺,Ca²⁺ content is positive and extremely significant(p<0.01),and that between CO₃^2- and SO₄^2- content also significantly positive,but that between Cl^- and HCO₃^- content negat ive.All these findings further suggest that the soils are heavy chloride saline soils.Organic matter contents of the soils are low averaging 11.46 g kg^-1 in the 0~30 cm soil layer.The content of total N and P of the soils are also very low,but the soils are rich in K. The results obtained from experimental area indicate that degradation and salinization of the soils is closely related to the local natural conditions and irrational human activities in the region.