Supplemental irrigation at the jointing stage of late sown winter wheat for increased production and water use efficiency

Context: The sowing of winter wheat (Triticum aestivum L.) in the winter wheat-summer maize double cropping system is considerably delayed due to late harvest of the maize. This delayed sowing leads to reduction in spike numbers and ultimately the yield. Supplemental irrigation at the jointing stage (SIJ) can effectively regulate the population of winter wheat, but few studies have reported the impacts of SIJ on water utilization, wheat stem number fluctuations, and yield formation of late sown wheat.Objective: The aim of this study was to determine the effects of sowing scheme accompanied with SIJ on wheat yield and water use efficiency (WUE).Methods: A two-year field experiment with two treatment factors (sowing date and irrigation schemes) in a split plot design was laid out during 2018-2020 in the wheat growing seasons. The main plots were divided into two levels: normal sown date (A1) and late sown date (A2). The split plots included two irrigation schemes: no SIJ (W0) and SIJ (W1).Results: The soil water consumption at 20-120 cm soil depth during sowing to jointing stage in late sown wheat (A2) was significantly lower than the normal sown wheat (A1) but it increased considerably at 100-200 cm soil depth from jointing to maturity in A2. SIJ (W1) in late sown wheat produced better yield and WUE than no SIJ (W0). Under W1 conditions, A2 significantly promoted water consumption from jointing to maturity compared with A1, but, because water consumption from sowing to jointing was very low, seasonal water consumption remained significantly low. Additionally, A2 showed accelerated dry matter accumulation after jointing, increased grain numbers per spike and per unit area, improved net photosynthetic rate (Pn) of flag leaf and postanthesis assimilate production.Conclusions: SIJ accelerated Pn and dry matter accumulation after jointing in late sown wheat, increased grain numbers per unit area, grain yield, and WUE without increasing seasonal water consumption. The seasonal water consumption in the normal sown period were higher. Although the number of spikes in normal sown wheat with higher water consumption, total stem number and dry matter accumulation before jointing was higher, after SIJ, the yield and WUE were lower than those of late sown wheat owing to the reduction in grain numbers per spike.Significance: This study explains how the sowing scheme and SIJ affect wheat yield and WUE, and demonstrates that SIJ was particularly crucial for late sown wheat to achieve the synergistic improvement of grain yield and WUE.