The Combined Effects of Irrigation and Nitrogen Fertilization on Yield and Water and Nitrogen Use Efficiency of Summer Maize

【Objective】 Water and nitrogen are integrative in their impacts on root uptake of water and nutrients from soil. The purpose of this paper is to screen for optimal combination of irrigation and nitrogen fertilization for sustaining summer maize production in north of Henan province. 【Method】 A 3-year experiment designed in randomized block was conducted from 2017 to 2019 in a maize field. It compared three irrigation schedules: rainfed (A1), irrigation twice (A2), and irrigation three times (A3) during growing season of the crop; for each irrigation treatment, there were two nitrogen fertilizations: applying 70%, 20% and 10% of the fertilizer as basal fertilization, at small trumpet and filling stage respectively (B1), applying 60%, 25% and 15% of the fertilizer as basal, at small trumpet and filling stage respectively (B2). During the experiment, we measured water and nitrogen use efficiency, as well as the grain yield. 【Result】 Irrigation amount and nitrogen fertilization in separation affected yield, water use efficiency (WUE) and irrigation water use efficiency (IWUE), as well as partial productivity of the nitrogen (NPFP) far more significantly than their combination. The impact of the treatments on yield, WUE and NPFP in 2017 and 2019 was ranked in the order of A3B2 > A2B2 > A3B1 > A2B1 > A1B2 > A1B1. In 2018, their impact on yield and NPFP was ranked in the order of A3B2 > A3B1 > A2B2 > A2B1 > A1B2 > A1B1 in 2018, and on WUE the ranking was A3B2 > A3B1 > A2B2 > A1B2 > A1B1 > A2B1. There were no significant differences in yield, WUE and NPFP between A3B1 and A2B2. A3B2 gave the highest yield, WUE and NPFP consistently over the three years, increasing by 20.2%~39.6%, 4.8%~10.9% and 20.2%~39.6%, respectively, compared with A1B2. During the experimental period, IWUE decreased as the irrigation frequency increased. The yield and NPFP of A2B2 were 11.3%~21.1% and 11.3%~21.2% higher than those of A1B2. 【Conclusion】 A3B2 was optimal for increasing yield while A2B2 was optimal for improving water use efficiency for maize production in northern Henan province.