Nutrient Management Strategies for Sichuan

Two monitored villages, set up in 2001, have been employed to study the wheat-corn system at Jianyang and the wheat-rice system at Chongzhou. Soil nutrient limitations were identified, nutrient variability maps were developed, and nutrient deficiencies were verified in the past. In 2005/07, the project continued to track crop response to application of fixed fertilizer rates over time.

At Jianyang, N is still the most limiting nutrient for both wheat and corn, followed by K and P. This is the first time that the effect of K has surpassed P in 7 years. Compared to the optimal (OPT) treatment, wheat yields were reduced by 1.0 t/ha (-41%) under the - N treatment, 319 kg/ha (-15%) under the - K treatment, and 276 kg/ha (-11%) under the - P treatment. Similarly, corn yields were reduced by 3.3 t/ha (-44%) under the - N treatment, 3.2 t/ha (-42%) under the - K treatment, and 1.2 kg/ha (-16%) under the - P treatment. This is the second year that corn yield reduction resulting from the omission of K has surpassed that resulting from the omission of P, indicating the K is being depleted at a faster rate than P at this location. Omission of magnesium (Mg) and zinc (Zn) from the OPT reduced corn yield by 1.2 t/ha (-16%) and 883 kg/ha (-12%), respectively. After two years of omitting Zn from the fertilizer program, corn yields have significantly responded to resumed Zn application, indicating that a 2-year residual response to a single Zn application would be suitable for corn production in this region.

Results at Chongzhou in 2007 differed from 2006. While N continued to be the most limiting for wheat and rice, it was now followed by K and then P. Wheat yields were reduced by 1.3 t/ha (-32%) under the - N treatment, 850 kg/ha (-21%) under the - K treatment, and 350 kg/ha (-9%) under the - P treatment. The reversed response of wheat to K over P in 2007 might be due to the warm winter that enhanced the availability of P in the soil. Rice yields were reduced by 1.5 t/ha (-21%) with the - N treatment, 1.0 t/ha (-15%) with the - K treatment, and 383 kg/ha with the - P treatment.

The soil pH decreased slightly in the upland soil at Jianyang and was maintained in the paddy field at Chongzhou. Available soil N and P contents were maintained and K fell slightly in the upland areas, while N and K continued to decline and P continued to increase in the paddy field. Sichuan-NMS01