Abstract:

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 m³ha^-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),K₂SO₄225 kg ha^-1, and ZnSO₄22.5 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 6134 kg ha^-1 for I₀, 7 515 kg ha^-1 for I₁, and 8 134 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 efficacy of the three irrigation treatments was 38 kg kg^-1and 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 schedulesshowed steady grain yield and high resource use efficiency for consecutive four years.

Key words: Winter wheat, Water-saving cultivation, Nitrogen use efficiency, High yield, Irrigation schedule