Nutrient Management Strategies for Chongqing

This on-going monitored village site was established in 2001 to study the effects of different P and K treatments on crop yield. Results are being used to guide fertilizer application for the county, track changes in soil fertility, and predict sustainability under different nutrient input regimes.

In the lowlands, rice yield in the zero fertilizer check has continually declined over the past 7 years to 54% of the optimal (OPT) treatment. Compared to the OPT, rice yield was 2,362 kg/ha (38%) lower with P omission, and 1,325 kg/ha (17%) lower with K omission. Application of Zn did not improve rice yields. However, the use of calcium-magnesium phosphate instead of single superphosphate, which introduced Mg and raised soil pH, produced 575 kg/ha (8%) more than the OPT. In the uplands, all three crops showed better responses to P than K. Omission of P reduced yield by 41% for wheat, 37% for corn, and 23% for sweet potato; without K, yield was reduced by 26% for wheat, 28% for corn, and 30% for sweet potato. Maximal crop yields in 2009 were 2,115 kg/ha for wheat, 5,715 kg/ha for corn, and 5,050 kg/ha for sweet potato, which were obviously lower than those obtained in 2008, most likely a result of drought in spring season.

As in previous years, annual application of P and K was of great importance in maintaining high crop yields and soil fertility status. Chongqing-NMS-05