Nutrient Management Strategies for Chongqing

Soil nutrient status and variability was determined and is being used to develop nutrient management techniques and systems capable of sustaining high yields and improving farmer profitability. Data from this and other field trials will be applied to an information systems database, which will be used to help formulate rational fertilizer regulation and management policies. Digital maps of nutrient variability within the site were generated in 2002 and effects of different phosphorus (P) and potassium (K) treatments on crop yield were examined in 2003. The focus for 2004 was to continue monitoring different fertilizer treatments in the fixed-site field trials.

Rice yields continued to trend upwards as a result of higher P and K application rates. Application of 135 kg P₂O₅/ha produced 2,033 kg/ha more grain, a 32% increased compared to the - P treatment. Application of 135 kg K₂O/ha produced an extra 2,980 kg/ha, a 58% increase compared to the - K treatment. Rice yields in the - P treatment fell from 8,400 kg/ha in 2001 to 6,320 kg/ha in 2004...a 25% reduction. Yields in the - K treatment fell from 8,020 kg/ha in 2001 to 5,170 kg/ha in 2004...a 36% reduction. In the uplands, the responses to P and K in corn, wheat and sweet potato were similar to the rice response. However, P and K application rates for wheat (150-90-90 kg N-P₂O₅-K₂O/ha) and sweet potato (75-60-120 kg/ha) were lower than those needed in rice. Annual application of P and K is essential to maintain high crop yields and soil fertility. Soil K reserves appear to be more susceptible to depletion than soil P. Chongqing-NMS05