Abstract:

Low fertilizer-nitrogen (N) use efficiency (FNUE) is a serious problem in rice production in China. The objective of this study was to explore the possibility to improve FNUE by adopting real-time N management (RTNM) and site-specific N management (SSNM). With an indica hybrid rice Shanyou 63 and a japonica cultivar Wuyujing 3 as materials, a plot experiment in field conditions was carried out during 2001–2003 to evaluate agronomic performance and FNUE under RTNM and SSNM. The results showed that grain yield in the plot without N application ranged from 5.5 to 7.4 t/ha (Table 4), indicating rather high indigenous N content in soil. Compared with farmers’ fertilizer practice (FFP), RTNM and SSNM increased grain yield by －4.4% to 7.0% and 0.2%–9.3%, agronomic efficiency (AE) of fertilizer-N by 195.7%–297.0% and 169.6%–276.4%, respectively (Table 5). SSNM was demonstrated in 20 farmers’ fields in two villages of Wuxi, Jiangsu Province in 2003 and 2004. AE, recovery efficiency (RE) and physiological efficiency (PE) of fertilizer-N in FFP in two years were only 2.8–6.7 kg grain/kg N, 33.7%–34.7% and 8.4–18.6 kg grain/kg N, respectively. SSNM reduced N rate by 38.7%–41.3%, increased grain yield by 2.5%–3.5%, and enhanced AE, RE and PE by 88.3%–117.7%, 34.0%–39.5% and 46.1%–61.6%, respectively (Table 6 and Table 7), when compared with FFP. Similar results were obtained on large-scale extension of SSNM in Jiangsu Province (Table 8). These results suggested that SSNM has great potential for improving FNUE without any sacrifice in the yield. AE and PE in SSNM in farmers’ fields were still very low in this study. Reasons for low FNUE and approaches to improving it were discussed.

Key words: Rice, Site-specific nitrogen management, Yield, Fertilizer-N use efficiency