Performance of site-specific nutrient management for irrigated rice in southeast China

Rice (Oryza sativa L.) yield increases in Zhejiang, China have slowed since 1985 despite the increasing use of hybrids and fertilizers. On-farm experi ments at 21 sites were conducted to evaluate a new approach for site-specif ic nutrient management (SSNM), Field- and season-specific N-P-K application s were calculated by ac counting for the indigenous nutrient supply, yield targets, and nutrient demand as a function of the interactions between N, P , and K. Nitrogen applications were fine-tuned based on season-specific rul es and field-specific monitoring of crop N status. The performance of SSNM was tested For Four successive rice crops. Compared with the current farmer s' fertilizer practice (FFP), average grain yield increased from 5.9 to 6.4 Mg ha-L while plant N, P, and K uptake increased by 8 to 14%, The gross re turn over fertilizer cost was about 10% greater with SSNM than with FFP, Yi elds were about 20% greater in late rice (hybrid cultivars) than in early r ice (inbred cultivars), but SSNM performed equally better than FFP in both seasons. Improved timing and splitting of fertilizer N increased N recovery efficiency from 0.18 kg kg(-1) in FFP plots to 0.29 kg kg(-1) in SSNM plot s. The agronomic N use efficiency (grain yield increase per kilogram fertil izer applied) was 80% greater with SSNM than with FFP, As defined in our st udy, SSNM has potential for improving yields and nutrient efficiency in irr igated rice. Future research needs to develop a practical approach for achi eving similar benefits across large areas without field-specific modeling a nd with minimum crop monitoring.