Improving water use efficiency and grain yield of winter wheat by optimizing irrigations in the North China Plain

Achieving the combination of high water use efficiency (WUE) and high yield is very important for the sustainable development of wheat production in the North China Plain (NCP). For this study, we investigated how to optimize timing of two irrigations to improve winter wheat grain yield and WUE under field conditions. No irrigation after sowing (WO) as a control, and six irrigation treatments as follows: irrigation of 75 mm each at late tillering and booting (TB), at late tillering and anthesis (TA); at late tillering and medium milk (TM), at jointing and anthesis (JA), at jointing and medium milk (JM) and at booting and medium milk (BM). Experiments were conducted between the 2014-2016 growing seasons. In all the treatments, JA achieved the highest grain yield (9,267.6 kg ha(-1)) and WUE (20.2 kg ha(-1) mm(-1)). Compared with TB, TA and TM, JA coordinated pre- and post-anthesis water use, reduced pre-anthesis and total evapotranspiration (ET), and increased post-anthesis water use amount and ratio; JA reduced biomass at anthesis, but optimized allocation of assimilation, increased spike partitioning index and maintained high fruiting efficiency, and thus obtained the highest grain number per m(2) (GN, 23.7 10(3)m(-2)). Meanwhile, JA optimized crop characteristics with appropriate leaf area index (LAI), delayed leaf senescence, extended grain filling duration by 1-3 days, then increased biomass post-anthesis and harvest index (HI). Compared with JM and BM, JA increased GN, biomass post-anthesis and grain yield as well. These results demonstrated that irrigation at jointing and anthesis could improve grain yield and WUE by increasing biomass post-anthesis, HI and GN. Therefore, we propose that under adequate soil moisture conditions before sowing, two irrigations at jointing and anthesis with 150 mm irrigation amount is the optimal limited irrigation practice for wheat production in Na.