Improvement of grain weight and crop water productivity in winter wheat by light and frequent irrigation based on crop evapotranspiration

Efficient use of scarce water resources to maximize yield and crop water productivity (WPc) is a common goal of sustainable and ecological agriculture in the North China Plain. To clarify whether light and frequent (LF) irrigation under the same or reduced amount of irrigation is beneficial to achieve this goal, and to further tap the water saving potential. Based on drip irrigation conditions, a three–year (2020–2023) field experiment was conducted to investigate the effect of four irrigation treatments (CK, conventional irrigation at the jointing and anthesis stages; LF1, 100 % ETc, ETc is the crop evapotranspiration; LF2, 75 % ETc, LF3, 50 % ETc) on yield, water consumption characteristics, leaf photosynthetic physiology and grain filling process. The results showed that compared with CK, LF1 and LF2 significantly increased the photosynthetic rate and chlorophyll content of flag leaves at 18 days after anthesis, promoted grain filling, and finally enhanced dry matter accumulation after anthesis, 1000–grain weight (TGW) and grain yield. LF irrigation management mode also increased the consumption of deep soil water (1.4–2.0 m), reduced soil water consumption and evapotranspiration, and significantly improved WPc and irrigation water productivity. However, LF1 and LF2 did not have significant yield enhancement in the wet year, but had one less irrigation than in the normal year. The LF2 achieved the highest WPc in three years (2.1 kg m–3), in the 25 % (37.5 mm) and 40 % (60 mm) less irrigation water in the normal and wet years, respectively. Meanwhile, the LF3 treatment reduced the number of spikes, TGW and dry matter accumulation to different degrees in three years, resulting in significantly lower yields (13.9 %–18.4 %), which cannot be used as a reference for an efficient irrigation system. Therefore, LF irrigation based on 75 % ETc is the best irrigation strategy to improve water utilization and yield in the North China Plain.