Research and Extension of Ag-lime Application in Sichuan

In the Sichuan basin, about 3.27 million hectares (ha) of farmland have soil pH below 6.5, among which 49,000 ha have pH below 5.5. Besides soil acidity, these soils usually have productivity problems related to a number of nutrient imbalances. This project was aimed at determining the optimal rates, timing, and placement of ag-lime for Sichuan province through a study on the relationship between soil acidity and lime requirement.

Field experiments in 2001 showed that the optimum pH for wheat was between 5.5 and 7.5. Corn planted after wheat seemed to be unresponsive to the residual effect of lime applied to wheat in the previous fall. However, liming with 5.5 t/ha of ground limestone in the summer prior to planting corn significantly increased corn yield by 645 kg/ha (14 percent).

Application of ag-lime with a balanced rate of fertilizer in the past two years has proven to be an effective measure in promoting growth and preventing diseases in the vegetables grown on the Chengdu plain. Vegetable yields could be increased by 20 to 30 percent or more. This technique can be applied to large areas of acid soils in southwest China, including Sichuan, Chongqing, Yunnan, and Guizhou. Adoption would greatly affect the potential for phosphorus (P) and potassium (K) use. SICHUAN-15