Research and Practice of Ag-lime Application for Ameliorating Acid Soils in Yunnan

The majority of soils in Yunnan province are acidic with pHs in the range of 4.0 to 5.5. Soil acidity adversely affects availability of indigenous soil P and K and those nutrients applied as fertilizers. Currently, Yunnan province has no history of applying aglime to farmland as an agronomic practice to improve soil fertility and productivity. This project is studying the limiting factors to yield and productivity, the relationship between soil acidity and lime requirement, and is determining the optimal rates, timing and placement of aglime for Yunnan province.

Results determined the lime requirement to be 13.8 t calcium carbonate (CaCO₃) /ha for laterite soil and 6.5 t CaCO₃/ha for yellow red soil. These treatments brought the respective soil pH levels to 6.3 and 5.7 and produced the highest dry matter yields. Among the different aglime materials investigated, calcitic limestone was the best for laterite soil, and dolomite was best for yellow red soil in pot trials. All the aglime materials significantly increased uptake of P, K, calcium (Ca), magnesium (Mg), iron (Fe), copper (Cu), and zinc (Zn), but reduced uptake of manganese (Mn) by broadbean seedlings grown in lateritic soil. In yellow red soil, aglime increased uptake of K and reduced uptake of Mn by broadbean seedlings. Liming in combination with balanced fertilizers is estimated to increase P and K fertilizer use on acid soils by about 90 and 200 kg/ha, respectively. YUNNAN-10