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

Past research has focused on identifying yield-limiting soil nutrients, screening suitable aglime materials, and determining the optimal rates, timing, and placement for aglime in crops sensitive to low soil pH. Ground calcite limestone was selected as the best lime source for the lateritic soil and ground dolomite was most suitable for the yellow earth soil. Optimal aglime rates ranged between 2.5 to 3.0 t/ha, which should be broadcast and thoroughly mixed with the plough layer at least one week before seeding. In 2003, our objective was to demonstrate and disseminate the technology to local leaders and farmers on a larger scale.

Aglime applied at the rate of 2 t/ha on broadbean planted in Dali Prefecture plus nitrogen (N), phosphorus (P), and potassium (K)...225-150-90 kg N-P₂O₅-K₂O/ha...increased yield by 11.4 t/ha (42%) and farmers’ net income by US$1,720/ha (50%) compared to farmers’ practice. Through field demonstrations and extension programs, local government and farmers are realizing the importance of maintaining soil pH and nutrients at optimal levels. Yunnan-10