Exchangeable Ca and Mg Contents in Various Purple Soils and their Effects on Ca and Mg Contents in Flue-cured Tobacco

In order to understand the contents of exchangeable Ca and Mg in different types of purple soils of Jiangxi and their effects on nutrients (Ca, Mg) distribution of flue-cured tobacco, the soil and tobacco samples were collected by point to point approach (namely the location of soil sample was same to that of the tobacco sample) in purple soil area of Jiangxi and were then determined in 2009. The results showed that in Jiangxi's purple soils, the exchangeable Ca was sufficient and greatly variable, while the exchangeable Mg was low and the ratio of exchangeable Ca to Mg was high, so the concentration of Ca in leaves was variable and the concentration of Mg was low;the concentration of Mg in tobacco leaves was neutral purple soil >acid purple soil >alkaline purple soil. In the neutral purple soil, the concentrations of Ca and Mg in difference position of leaves were not significant difference, but in the acidic and alkaline purple soils the concentrations of Ca and Mg in the upper leaf were higher than those in the middle and lower leaves. Soil exchangeable Ca was significantly positive correlation to Mg, and also was positively correlative to pH, organic matter, nutrients (N, P, K, S), and was extremely significant and negative correlated to soil trace elements.