Effects of water-nitrogen coupling under different irrigation methods on water and nitrogen use efficiency of winter wheat

Abstract

【Objective】 Irrigation and nitrogen fertilization are critical to maintaining agricultural production in most regions in China. The purpose of this paper is to investigate the effect of water-nitrogen coupling under different irrigation methods on water and nitrogen use efficiency by winter wheat in attempts to provide an optimal irrigation-fertilization for wheat production in Henan province. 【Method】 The experiment was conducted in a field with Jimai 22 variety used as the model plant. We compared two irrigation methods: wide furrow irrigation (F) and border irrigation (Q), each having three irrigation amounts by controlling the lower soil moisture for irrigation at 60% (W1), 70% (W2) and 80% (W3) of the field capacity, respectively. For each irrigation treatment, there were three nitrogen fertilizations by applying 120 (N1), 220 kg/hm2 (N2) and 320 kg/hm2 (N3) of nitrogen. Using the measured data and genetic algorithm, we optimized the irrigation and nitrogen fertilization for jointly maximizing wheat yield, water use efficiency, nitrogen partial factor productivity, soil nitrogen residue and output-input ratio. 【Result】 ① Irrigation method, the lower soil water content for irrigation and nitrogen application all had a significant effect on water use efficiency, nitrogen partial factor productivity of the wheat, as well as soil nitrate residue in the 0-100 cm soil and the wheat grain yield (P<0.01). With the increase in nitrogen application and the lower soil water content for irrigation, the grain yield and water use efficiency of the wheat both increased first followed by a decrease. ② Grain yield, water use efficiency and the net profit were maximum in F+W2+N2, reaching 9 686.93 kg/hm2, 1.97 kg/m3 and 15 142.93 yuan/hm2, respectively, which were 44.71%, 56.65% and 56.59% higher than those in F+W1+N1. 【Conclusion】 The optimal irrigation and nitrogen fertilization for winter wheat in the studied area are: wide ridge furrow irrigation with the lower limit for irrigation being 70% of the field capacity, coupled with 245.46 kg/hm2 of nitrogen application.

Keywords

• water-nitrogen coupling
• water use efficiency
• nitrogen partial factor productivity
• yield
• value to cost ratio
• soil nitrogen residue