Characteristics of Exchangeable Calcium and Magnesium in Tobacco Growing Soils in Kunming

In order to investigate the characteristics of exchangeable calcium, exchangeable magnesium and Ca/Mg ratio in flue-cured tobacco growing soils in Kunming, 1000 representative samples were collected with GPS positioning and analyzed. The results showed that:1) The contents of exchangeable calcium and magnesium were rich in the soil samples with the average value of 2728.36 and 294.71 mg/kg, respectively; and the samples with the Ca/Mg ratio higher than 10, which induced potential magnesium deficiency accounted for 37.50% of the total samples. 2) The soil exchangeable calcium, exchangeable magnesium and Ca/Mg ratio were lower at the higher altitude areas than those at the lower altitude areas. 3) Soil textures slightly affected the contents of exchangeable calcium and magnesium, however Ca/Mg ratio was relatively higher in soil with heavy texture in general. 4) There was positive correlation between soil pH and the contents of exchangeable calcium and magnesium.