Utilization of Water and Nitrogen and Yield Formation under Three Limited Irrigation Schedules in Winter Wheat

Water shortage is a great challenge in winter wheat(Triticum aestivum L.) production worldwide.Studies on wheat physiology and ecology have been carried out aiming at yielding more grains with less consumptions of water and nitrogen fertilizer.Cultivation techniques based on limited irrigation and nitrogen application are highly emphasized in North China Plain,where water stress is the most major problem in regular years.In Wuqiao area,Hebei province,China,a series cultivation systems have been established with distinct effects of high yield and small water consumption.The principle measure in the technique system was controlling the irrigation frequency and water amount.The purpose of this study was to disclose the mechanism of high-yielding and high resource use efficiency in the cultivation system established in Wuqiao.In the consecutive growing seasons from 2004 to 2008,field experiments were conducted at the Wuqiao Experimental Station of China Agriculture University under three limited irrigation schedules,i.e.,no irrigation in spring(I0) ,750 m3 ha-1 of water at jointing(I1) and each 750 m3 ha-1 of water at jointing and anthesis(I2) .Fertilizers were only applied before sowing,including urea 225 kg ha-1,(NH4) 2HPO4 300 kg ha-1(thus,the total nitrogen was 157.5 kg ha-1) ,K2SO4 225 kg ha-1,and ZnSO4 22.5 kg ha-1.The characteristics of water and nitrogen use and the formation of grain yield were investigated at jointing,booting,anthesis,and maturity stages.The results showed that the average yield was 6 134 kg ha-1 for I0,7 515 kg ha-1 for I1,and 8 134 kg ha-1 for I2 treatment,and the average total evapotranspiration was in the order of 3 334,3 829,and 4 270 m3 ha-1.The ratio of soil water consumption to total evapotranspiration was 67%,49%,and 38% in I0,I1,and I2 treatments,respectively.The water use efficiency ranged from 1.9 to 2.0 kg m-3 with no significant differences among treatments.This indicated that approximately 52.6 m3 of water was required for yielding 100 kg of grains.Under the nitrogen application level of 157.5 kg ha-1,the average total nitrogen accumulation was 163,198,and 212 kg ha-1 in I0,I1,and I2 treatments,respectively.Consistent results with slight variations were observed in the total nitrogen accumulation across years.The average nitrogen use efficiency of the three irrigation treatments was 38 kg kg-1 and there were no significant differences among treatments.In terms of the characteristics of plant population,the leaf area index(LAI) at booting and anthesis,as well as the LAI for the top three leaves were not significantly different between I1 and I2 treatments,but they were significantly higher than those in I0 treatment.The LAI for the top three leaves and non-leaf organs green area index(NAI) above flag leaf ranged from 2.6 to 3.8 and from 2.7 to 3.6,respectively.The ratios of non-leaf organs green area above flag leaf to the uppermost three leaf area and total leaf area were more than 1.0 and 0.7,respectively.Three limited irrigation schedules showed steady grain yield and high resource use efficiency for consecutive four years.