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 Zhouzhou. In past field studies, soil nutrient limitations were identified, nutrient variability maps were developed, and nutrient deficiencies were verified. In 2005, crop response trends were similar to the previous years' results, although the intensity of soil nutrient deficiencies appears to be increasing over time. Clear crop-specific nutrient limitations have also been observed.

At Jianyang, nitrogen (N) is most limiting for both wheat and corn, followed by phosphorus (P) and potassium (K). Compared to the optimal treatment, wheat yields were reduced by 2.1 t/ha (-32.3%) under the - N treatment, 816 kg/ha (-19%) under the - P treatment, and 669 kg/ha (-15.8%) under the - K treatment. Simarily, corn yields were reduced by 4.5 t/ha (-246%) under the - N treatment, 2.4 t/ha (-59%) under the - P treatment, and 678 kg/ha (-12%) under the - K treatment. At Chongzhou, N, P, and K were severely limiting for wheat, yet only N and K appeared limiting in rice. Phosphorus responses were larger for the winter crop of wheat and upland corn, and K application appeared more critical in the wheat-rice rotation. Wheat yields were reduced by 3.1 t/ha (-111%) under the - N treatment, 1.8 t/ha ( -44.6%) under the - K treatment, and 1.5 t/ha (-32.5%) under the - P treatment. Rice yields were reduced by 905 kg/ha (-28.9%) with the - N treatment and 275 kg/ha (-7.3%) with the - K treatment.

The - N treatment significantly reduced grain protein content in all three crops. Depletion of available N, P, and K was observed for each nutrient omission treatment. After 4 years of manganese (Mn) and zinc (Zn) application, these nutrients were no longer yield-limiting and appeared to be available in excessive amounts.

This study has provided a better understanding of the soil nutrient status and crop responses to applied nutrients, and thus gives local technicians and planners insight into the crop- and season-specific nutrient management strategies for two important crop management systems in Sichuan. Sichuan-NMS01