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

The majority of soils in Yunnan province are acidic with pH ranging from 4.0 to 5.5. Soil acidity can considerably reduce the availability of indigenous soil phosphorus (P), potassium (K), and other nutrients as well as those applied as fertilizers. Yunnan currently has no history of lime application to farmland as an agronomic practice to improve soil fertility and productivity. This project, in studying the limiting factors related to soil fertility and poor productivity, is examining the relationship between soil acidity and lime requirement, and determining the optimal rates, timing and placement of ag-lime.

Among all treatments tested, [nitrogen (N)PK, NPK+molybdenum (Mo), NPK+burned lime, NPK+slaked lime, NPK+ground limestone, NPK+ground dolomite, NPK+ground limestone+ground dolomite, NPK+slaked lime+straw, and NPK+baked lime+straw], NPK+ground limestone was the best treatment in improving broadbean and corn yield in lateritic soils. NPK+ground dolomite was the best treatment for the yellow earth soils. The combination of farmer practice (30-120-150 kg N-P₂O₅-K₂O/ha for broadbean and 150-120-60 kg N-P₂O₅-K₂O/ha for corn) plus 4.5 t/ha of ground limestone to the lateritic soil and 2.8 t/ha to the yellow earth soil increased broadbean yield by 1,570 kg/ha (about 50 percent) and 1,680 kg/ha (about 56 percent) at the respective sites. Similarly, NPK plus 5.6 t/ha of ground dolomite to the lateritic soil and 2.8 t/ha to the yellow earth soil increased corn yield by 2,730 kg/ha (32 percent) and 2,810 kg/ha (27 percent), respectively.

The different response of the two soil types to limestone and dolomite was due to a more severe calcium (Ca) deficiency in the lateritic soil and a more severe magnesium (Mg) deficiency in the yellow earth soil. In general, ag-lime treatments improved soil nutrient availability and crop uptake. The practice of liming acid soil can be a very economic practice for farmers of the region. YUNNAN-10