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

The majority of soils in Yunnan Province are acidic, with pH measurements ranging between 4.0 to 5.5. Acid-induced adverse soil conditions include reduced availability of indigenous and applied sources of soil phosphorus (P), potassium (K), and various other nutrients. To date, aglime application to farmland is not widely practiced. This project is studying the relationship between soil acidity and lime requirement and aims to determine the optimal rates, timing, and placement of aglime for Yunnan Province.

All aglime treatments significantly increased corn yield but ground calcitic limestone was the best treatment for improving corn yield grown on lateritic soils [i.e., red, tropical soil rich in iron (Fe) and aluminum (Al) hydroxides]. Ground dolomite appeared best for the yellow earth soil. The different response of these two soils to calcite and dolomite was due to a more severe calcium (Ca) deficiency in the lateritic soil, versus a magnesium (Mg) deficiency in the yellow earth soil. Common farmer practice for corn fertilization amounts to 150-120-60 kg N-P₂O₅-K₂O/ha for both soil-types. The addition of 2.8 t/ha of ground calcite limestone to the laterite soil and 2.8 t/ha of dolomite limestone to the yellow earth increased yield of corn by 2,320 kg/ha (59%) and 4,730 kg/ha (52%), respectively. Yield improvements were mainly attributed to improved availability of P, K, Ca, Mg, copper (Cu), and zinc (Zn) as well as reduced availability of Al, Fe, and manganese (Mn). Liming acid soil can be a very effective and economic practice to improve productivity and farmers’ income. Yunnan-10