Effects of drought on N absorption and utilization in winter wheat at different developmental stages

Aims Our objective was to investigate the effects of different water stress levels on yield,N absorption,allocation and utilization in winter wheat cultivars 'Shijiazhuang 8'(drought resistant) and 'Yanmai 20'(drought sensitive) during different growth durations.Methods We divided the growing stages of winter wheat into recovering-jointing,jointing-flowering and late filling.Soil water levels based on field capacity were 75%–80%(control,full water supply or well-watered),65%–70%(light drought stress),55%–60%(medium drought stress) and 40%–45%(severe drought stress) from winter wheat seeding to maturity and were controlled by irrigation and mobile rain shelters.Important findings The drought resistant cultivar 'Shijiazhuang 8' had a higher grain yield than 'Yanmai 20' under drought stress,and medium drought stress in all the three durations can increase winter wheat yield.Drought stress in the jointing-flowering stage has the greatest effects on N assimilation and translocation in winter wheat,the second greatest being in the recovering-jointing stage,while that in late filling stage has few effects.Both medium and severe drought stress during different growth durations will lower the translocation of stored nitrogen before anthesis into grain,as well as N utilization rate and productivity;on the other hand,light drought stress in the recovering-jointing and late filling stages can improve the translocation of stored N into grain as well as N utilization rate and productivity.Under drought stress,N accumulation in grain of drought-resistant 'Shijiazhuang 8' relies more on the retranslocation of stored N before anthesis,while that of 'Yanmai 20' relies more on the N accumulation and translocation after anthesis.Considering yield and N translocation of wheat,light drought stress during the recovering-jointing and late filling stages is necessary,as well as sufficient irrigation during jointing-flowering stage,so as to improve N accumulation and partitioning.