Nutrient Management Strategies for Chongqing

Soil nutrient status and variability was determined and is being used to develop nutrient management techniques and systems capable of sustaining high yields and improving farmer profitability. Data from this and other field trials will be applied to an information systems database, which will be used to help formulate rational fertilizer regulation and management policies. Digital maps of nutrient variability within the site were generated in 2002. The focus for 2003 was to examine soil nutrient balances for different fertilizer treatments applied to fixed-site field trials.

Results substantiated earlier findings (2002) that nitrogen (N) and phosphorus (P) uptake by rice was usually less than amounts applied, thus resulting in a build-up of soil reserves. In contrast, potassium (K) removal was always greater than amounts applied. In upland soils, nutrient deficits occurred in wheat or corn when application rates for N, P₂O₅, or K₂O fell below 50 kg/ha. A similar trend was found for P and K in sweet potato, but N deficits were still apparent with rates above 113 kg/ha. The optimum fertilizer treatment was 135-90-90 kg N-P₂O₅-K₂O/ha for rice, 150-90-90 kg/ha for wheat, 225-(100 to 120)-150 kg/ha for corn, and (100 to 120)-(50 to 60)-(100 to 120) kg/ha for sweet potato. Chongqing-NMS05