Nutrient Management Strategies for Chongqing

This monitored village was established in 2001. 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 past 5 years, rice yields for the zero fertilizer check have been declining, but now appear to be stable at about 64% of the optimum (OPT) treatment yield. This phenomenon is also observed in other hilly areas if the particular field is located in the valley and can receive irrigation water and nutrients from adjacent fields. Rice yield has continued to increase in response to increased rates of P and K. Compared to the P and K omission treatments, yields for the OPT treatment were 1,803 kg/ha (34%) and 1,442 kg/ha (26%) higher, respectively. Rice yields under zero P input have varied from 8.4 t/ha in 2001 to 5.1 t/ha in 2006. Yields under zero K input varied from 8.0 t/ha in 2001 to 5.5 t/ha in 2006. This yield reduction is commonly seen in confined plots of long-term rice experiments, and is most likely due to the adverse effects of continuously growing the same crop without rotation. Rice responded to applied zinc (Zn) fertilizer and showed a 5% yield increase compared to the OPT treatment. In the uplands, wheat and corn showed better responses to applied P than K, but sweet potato had a better response to K. Without P, yields were reduced by 30% in wheat, 19% in corn, and 11% in sweet potato. Without K, yields were reduced by 24% in wheat, 18% in corn, and 27% in sweet potato, an indication of the importance of adequate K nutrition in tuber crops. Annual application of P and K is of great importance to maintain yield and soil fertility. It appears that soil K reserves are being depleted faster than soil P. Chongqing-NMS-05