Effects of irrigation amount on water use characteristics and grain yield of wheat under different nitrogen application rates.

A field experiment was conducted to examine the effects of irrigation amount on the water consumption, flag leaf physiological characteristics, and grain yield of wheat under the nitrogen application rates 180 kg∙hm^-2(N₁₈₀) and 240 kg∙hm^-2(N₂₄₀). Four irrigation regimes were designed, i. e. , no irrigation during whole growth period (W₀), irrigation with 60 mm water before sowing (W₁), irrigation with 60 mm water before sowing and at jointing stage, respectively (W₂), and irrigation with 60 mm water before sowing, at jointing stage, and at flowering stage, respectively (W₃). In treatment W₀, the water consumption amount below 100 cm soil layer was lower than that in other treatments; and in treatments W₁ and W₂, the water consumption amount in 100-200 cm and 0-200 cm soil layers was higher than that in treatment W₃. The soil water consumption amount in 0-80 cm soil layer, the consumption percentage from flowering to maturing stage, and the total water consumption amount were all higher under N₂₄₀ than under N₁₈₀. At mid and late grain-filling stages, the relative water content (RWC) and water potential (ψ_w) of flag leaves were higher in treatments W₂ and W₃ than in treatments W₀ and W₁. The RWC and ψ_w at late grain-filling stage were higher in treatments N₂₄₀ W₀ and N₂₄₀ W₁ than in N₁₈₀ W₀ and N₁₈₀ W₁, respectively, but had no significant differences between treatments N₂₄₀W₂ and N₁₈₀W₂, and N₂₄₀W₃ and N₁₈₀W₃. In this study, treatment N₁₈₀W₂ had the higher grain yield, water use efficiency (WUE), and nitrogen use efficiency, while over-irrigation increased the water consumption amount, and decreased the WUE, irrigation water use efficiency, and irrigation benefit. [ABSTRACT FROM AUTHOR]