Opportunities for yield increases and environmental benefits through site-specific nutrient management in rice systems of Zhejiang province, China

Environmental pollution by nitrogen (N) leaching or runoff from rice fields and high pesticide use has become serious concern in China. Average N application rates are high and fertilizer-N use efficiency is low compared with other major rice growing countries. In Zhejiang, rice farmers apply 150-250 kg ha -1 fertilizer N and 7-10 sprays of pesticides per season to maintain yield levels of 5.5 -8.0 t ha -1 . Fertilizer and pest management strategies of farmers are not based on plant nutrient demand and pest control requirements, and appear to be largely directed at risk avoidance. To provide farmers with options for high yielding, yet more resourceful management options, a new site-specific nutrient management (SSNM) approach was developed at Zhejiang University in collaboration with the International Rice Research Institute (IRRI). The main objective of t his paper is to introduce SSNM as an important component of sustainable resource management in rice ecosystems. The approach comprises of guidelines that allow farmers to adjust domain- and season-specific fertilizer recommendations to actual growing conditions in their fields. Recommendations are developed for profitable grain yield targets considering plant nutrient demand, indigenous nutrient supply, nutrient balance, nutrient use efficiency, as well as socioeconomic factors. The agronomic performance of SSNM has been evaluated in farmers’ fields in the past seven years (1998-2004). With SSNM, average grain yield increased by about 0.5 t ha -1 over the farmers’ practice, while N use efficiency increased significantly. About 30% of both fertilizer N and pesticides could be reduced through adoption of SSNM, which would effectively eliminate an unnecessary source