Alternate wetting and drying irrigation and controlled-release nitrogen fertilizer in late-season rice. Effects on dry matter accumulation, yield, water and nitrogen use

Alternate wetting and drying (AWD) irrigation has been widely adopted to replace continuous flooding (CF) irrigation for saving water and increasing water productivity in irrigated rice systems. There is limited information on the performance of controlled-release nitrogen fertilizer (CRNF) under AWD conditions. The objectives of this study were to investigate the effects of four N managements (control, N0; conventional urea at 240 kg N ha−1, UREA; controlled-release bulk blending fertilizer at 240 kg N ha−1, BBF; polymer-coated urea at 240 kg N ha−1, PCU) under CF and AWD water regime on dry matter accumulation (DMA), grain yield, water and N use efficiencies (WUE/NUE) in late-season rice. Compared with CF, AWD significantly reduced the number of irrigation (5 in 2010 and 3 in 2011) and the amount of irrigation water (41.9% in 2010 and 28.0% in 2011). Thus, field water level was shallowed and rainwater storage capacity and usage were improved, leading to reduced surface runoff. AWD performed comparably to or better than CF on plant biomass (root, shoot, panicle, shoot, and whole rice), yield, WUE and NUE, while N fertilization significantly enhanced those parameters. BBF performed comparably with urea on DMA, yield, WUE and NUE, while PCU significantly improved those traits compared with BBF and urea. The interactions of W × N on DMA, grain yield, total N uptake, and NUE were not significant, while those on WUE were significant. The combined AWD and PCU treatment enhanced root and panicle dry matter accumulation and partitioning, effective panicles per m2, spikelets per m2, grain filling and harvest index. As a result, it increased grain yield and subsequently increased WUE and NUE with reduced water input by AWD and enhanced N utilization by PCU. Our results suggested that the new water and N management combination can be an effective means to save water, promote rice production, and improve WUE and NUE for late-season rice.

► The performance of two controlled-release N fertilizers (BBF and PCU) under two water regimes: CF and AWD in comparison with urea were evaluated.
► AWD performed comparably to or better than the CF.
► BBF performed comparably with urea, while PCU significantly improved agronomic performance compared with BBF and urea.
► There was lack of interactions between water regime and N-source on yield and NUE, but it did exist on WUE.
► The AWD and PCU combination was recommended for the late-season rice.