Regular Nitrogen Application Increases Nitrogen Utilization Efficiency and Grain Yield in Indica Hybrid Rice

On the basis of research and practical production experience of many years, regular nitrogen fertilizer application (RFA) was used to improve rice ( Oryza sativa L.) yield and increase nitrogen utilization efficiency (NUE). Two field experiments (manually transplanted rice with three indica hybrid rice cultivars and four N treatments, mechanically transplanted rice with eight N applications) were conducted in 2011 and 2012, to investigate the effects of RFA on rice yield and NUE. The results showed that RFA increased the total amount of N uptake in the plants and improved NUE when compared with the farmers’ nitrogen fertilizer practices (FFP). The average increment in agronomy efficiency (AE), recovery efficiency (RE), and partial factor productivity for applied nitrogen (PFP) were 12.16, 10.91, and 6.01% for the mechanically transplanted rice and 30.81, 65.57, 6.18% for the manually transplanted rice. The main reason for the increase was the improvement in N concentration of the plant organs. For RFA, the grains per panicle was 12.15 and 7.59% higher than that of FFP, which was the main reason for the 6.19 and 3.33% increase in the yield of the manually and mechanically transplanted rice, respectively. To the best of our knowledge, this is the first RFA strategy to be applied, and the jointing stage and 15 to 20 d after the jointing stage are the key periods for increasing the total amount of N uptake and grain yield; this strategy should be widely applied for indica hybrid rice production. Core Ideas Regular nitrogen fertilizer application significantly increased grains per panicle and then improve rice yield. Regular nitrogen fertilizer application improved plant N concentration and then increased N use efficiency. Jointing stage and 15 to 20 d after jointing stage are the two key stages to apply N fertilizers. Regular N fertilizer application is suitable for both manually and mechanically transplanted rice.