The effect of water-nitrogen coupling on growth of summer maize in seasonally arid areas and water-nitrogen production function in southwestern China

【Objective】 Water and nitrogen are two most important factors affecting crop growth. Their acquisitions by crops interactively affect by each other. The purpose of this paper is to study the interactive effect of water-nitrogen coupling on development of summer maize during its key growing stages in seasonally arid areas in southwestern China. 【Method】 The experiment was conducted from June to October 2022 using lysimeters inside a rain-shelter at Dujiangyan Irrigation Experimental Station in Sichuan province. The variety Zhongyu No.3 was used as the model plant, and the control (CK) was irrigation of 100% of evapotranspiration (ET) combined with 300 kg/hm2 of nitrogen fertilization as used by local farmers. There were two irrigation treatments by irrigating 75% (HW) and 50% (LW) of the water used in the CK, and three nitrogen treatments by fertilizing 85% (N1), 70% (N2) and 55% (N3) of the fertilizer used in the CK at jointing-tasseling stage (Ⅱ) and tasseling-filling stage (Ⅲ), respectively. In each treatment, we measured the changes in growth, yield, water use efficiency (WUE) and nitrogen partial productivity (NPFP) of the maize at its key growing stages. The production function of the water and nitrogen was calculated using the Jensen model. 【Result】 The jointing-tasseling stage was the key stage for vegetative growth of the maize. A suitable water-nitrogen coupling can increase the yield, WUE and NPFP of the crop. Compared with CK, the combinations II+HW+N2, III+HW+N1 and III+HW+N2 saved 12.78%, 9.77% and 9.77% of water, and 9.0%, 4.5% and 9.0% of nitrogen, respectively, while increasing grain yield by 1.31%, 4.32% and 4.50%, WUE by 28.39%, 14.83% and 8.52%, and NPFP by 11.33%, 10.42% and 8.52% respectively. The water-nitrogen production function was well described by the Jensen model with the R2 being 0.761 9. The sensitivity index of water-nitrogen coupling at jointing-tasseling stage was 0.152, higher than 0.074 at the tasseling-filling stage. 【Conclusion】 Our results showed that the combinations II+ HW+N2 and III+ HW+N2 are optimal for maintaining high yield yet improving water and nitrogen use efficiency of the maize. They can be used as an improved irrigation and fertilization for maize production in the studied region and its periphery. The water-nitrogen production function is well described by the Jenson model.