Delayed timing of tillering fertilizer improved grain yield and nitrogen use efficiency in japonica rice

During conventional fertilization, Nis applied before or during the early growth stages of rice (Oryza sativa L.), usually resulting in N loss and waste. Therefore, developing effective N management practices to reduce N losses and increase rice yield and N use efficiency (NUE) will be beneficial to farmers and the environment. Here, the effects of delayed timing and reduced N fertilizer on the yield and NUE of japonica rice grown in Shenyang, China, were investigated in 2016 and 2017. Fertilization during the early tillering stage had no significant effect on the leaf area index (LAI), amount of bleeding sap, dry matter accumulation, or N accumulation by the mid-tillering (nine-leaf) stage. After the jointing stage, compared with conventional N treatment, delayed timing of tillering fertilization from 5.5-leaf stage (7 d after transplanting) to the nine-leaf stage increased root activity and enhanced nitrate reductase and glutamine synthetase activities in rice leaves. Greater N accumulation from the jointing to grain-filling stages increased LAI and dry matter accumulation. Average grain yield as a result of delayed N fertilization was 8.6 and 30.7% higher than conventional N treatment. Given the results, optimizing N application rates and timing improved NUE and decreased the amount of N fertilizer needed for maintaining and increasing yield. Collectively, these results indicate that the delayed timing of tillering N fertilizer improves rice yield and NUE.