Distribution and Affecting Factors of Soil Cation Exchange Capacity in Watershed of the Loess Plateau

Through analyzing 54 soil samples of 27 sample points in Shanbei watersheds which included Zhujiagou,Zhifanggou and Nihegou,the distribution and affecting factors of soil cation exchange capacity were discussed by statistical method.The results showed that:(1)The soil CEC had obvious zonality,and the CEC value increased markedly from north to south in three selected typical watersheds.(2)The vertical zonality changes displayed that soil CEC increased with height reduced in the same watershed;the CEC value of surface layer were higher than the lower in the same profile.Based on the premise that the clay minerals in the same basic types,by using the correlation analysis and stepwise regression testing,the conclusion as followed: The main factors that influenced CEC value changes had pH,the soil clay content and the organic matter content;the effect of silt content was small;while the sand content showed significant negative correlation with CEC.