Fertilization for High Yields in Corn—Sweet Potato—Wheat Rotation：A Systematic Approach to Nutrient Limiting Factors of Soils in Chongqing,China

A systematic approach was adopted to investigate the nutrient limiting factors in gray-brown purple soils and yewwlow soils derived from limestone in Chongqing,China,to study balanced fertilixation for corn,sweet potato and wheat in rotation. The results showed that N,P and K were deficient in both soils, Cu,Mn S and Zn in the gray-brown purple soils and Ca,Mg,Mo and Zn for the yellow soils. Balanced fertilizer application increased yields of corn,sweet potato and wheat by 28.4%,28.7% and 4.4%, respectively, as compared to the local farmers' practice. The systematic approach can be considered as one of the most efficient and reliable methods in fertility study.