Nutrient Management Strategies for Sichuan

Two monitored villages were established in 2001 to study the wheat-corn system at Jianyang and the wheat-rice system at Chongzhou. In past field studies, soil nutrient limitations were identified, nutrient variability maps were developed, and nutrient deficiencies were verified. In 2005 and 2006, the project continued to track the crop response to fixed fertilizer application rates.

At Jianyang, N is still most limiting for both wheat and corn, followed by P and K. Compared to the optimum (OPT) treatment, wheat yields were reduced by 1.8 t/ha (38%) under the N omission treatment, 874 kg/ha (18%) under the P omission treatment, and 517 kg/ha (11%) under the K omission treatment. Similarly, corn yields were reduced by 2.3 t/ha (71%) under the N omission treatment, 673 kg/ha (20%) under the P omission treatment, and 784 kg/ha (24%) under the K omission treatment. This is the first year that the corn yield reduction resulting from K omission has surpassed that of the P omission treatment, and this indicates that K is being depleted faster than P at this location.

At Chongzhou, K became most limiting for wheat for the first time in 5 years, followed by P and N, while only N and K appeared limiting in rice. Results further indicate the importance of P for the winter crop of wheat and upland corn, and K in the wheat-rice rotation. Wheat yields were reduced by 636 kg/ha (12%) under the N omission treatment, 1.05 t/ha (20%) under the P omission treatment, and 1.99 t/ha (39%) under the K omission treatment. Rice yields were reduced by 1.73 t/ha (25%) with the N omission treatment and 1,447 kg/ha (21%) with the K omission treatment. After 4 years of manganese (Mn) and zinc (Zn) application, these two nutrients were no longer yield-limiting and appeared to be available in excessive amounts, even after 2 years without any application. Sichuan-NMS-01