Dry matter, harvest index, grain yield and water use efficiency as affected by water supply in winter wheat

Food production and water use are closely linked processes and, as competition for water intensifies, water must be used more efficiently in food production worldwide. A field experiment with wither wheat (Triticum Aestivum L.), involving six irrigation treatments (from rain-fed to 5 irrigation applications), was maintained in the North China Plain (NCP) for 6 years. The results revealed that dry matter production, grain yield and water use efficiency (WUE) were each curvilinearly related to evapotranspiration (ET). Maximum dry matter at maturity was achieved by irrigating to 94% and maximum grain yield to 84% of seasonal full ET. A positive relationship was found between harvest index (HI) and dry matter mobilization efficiency (DMME) during grain filling. Moderate water deficit during grain filling increased mobilization of assimilate stored in vegetative tissues to grains, resulting in greater grain yield and WUE. Generally, high WUE corresponded with low ET, being highest at about half potential ET. At this location in NCP, highest WUE and grain yield was obtained at seasonal water consumption in the range 250-420 mm. For that, with average seasonal rainfall of 132 mm, irrigation requirements was in the range of 120-300 mm and due to the deep root system of winter wheat and high water-holding capacity of the soil profile, soil moisture depletion of 100-150 mm constituted the greater part of the ET under limited water supply. The results reveal that WUE was maximized when around 35% ET was obtained from soil moisture depletion. For that, seasonal irrigation was around 60-140 mm in an average season.