Nutrient Management Strategies for Chongqing

This ongoing monitored village was established in 2001 to monitor the effects of different phosphorus (P) and potassium (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. This was the final year report.

In the lowlands, rice responded better to P than K. Compared to the optimal (OPT) treatment, rice yield was 3,068 kg/ha (40%) lower under the - P treatment, and 1,236 kg/ha (14%) lower under the - K treatment. Similar to what was observed in 2009, application of zinc (Zn) did not improve rice yields, whereas application of calcium-magnesium phosphate instead of single superphosphate by introducing magnesium and raising basicity produced 153 kg/ha (2%) more than the OPT, 6% lower than in 2009. Rice yield in the zero fertilizer check in the past eight years has continually decreased to 55% of the OPT.

In the uplands, all three crops showed significant responses to added P and K. Omission of P reduced yield by 47% for wheat, 21% for corn, and 20% for sweet potato; without K, yield was reduced by 14% for wheat, 23% for both corn and sweet potato. P rate at 90 kg P₂O₅/ha always produced highest crop yields than the lower P rates. In comparison of yields of the nutrient omission plots among the three crops in nine year experiment period, wheat showed better response to P than K, and yields at the P omission plot kept decreasing with time for wheat and at the P or K omission plot for sweet potato. Corn yields at the P or K omission plot remained fluctuating between 80-60% of the OPT. 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