Effect of water-nitrogen coupling on water and nitrogen use efficiency of rotated winter wheat and summer maize under subsurface drip irrigation

【Objective】 Root acquisitions of water and nutrients and their subsequent translocation and consequences for crop growth are complex processes interactively influenced by a myriad of biotic and abiotic processes. This paper aims to experimentally find the optimal irrigation and nitrogen fertilization for rotated winter wheat and summer maize under subsurface drip irrigation. 【Method】 The experiment was conducted in a wheat-maize rotation field. The irrigation treatments for the winter wheat were 2 580 m3/hm2 (W1), 2 240 m3/hm2 (W2), 2 020 m3/hm2 (W3), 1 560 m3/hm2 (W4). For the summer maize, the irrigation treatments were 1 306 m3/hm2 (W1), 1 088 m3/hm2 (W2), 814 m3/hm2 (W3), 650 m3/hm2 (W4). For each irrigation treatment, there were two nitrogen fertilizations for the two corps: 180 kg/hm2 (F1) and 100 kg/hm2 (F2). During the experiment, we measured soil moisture, nitrogen content, dry mass of the shoots and grain yield of the two crops at different growth stages. We also calculated water consumption, water use efficiency, partial nitrogen fertilizer productivity of the two crops to assess the impact of water-nitrogen coupling on these traits. 【Result】 For winter wheat, the W2F1 was the optimal water-nitrogen coupling which gave the highest grain yield. For summer maize, its grain yield increased with irrigation amount for both fertilization treatment. Soil nitrogen residual content was higher in F1 than in F2. With the increase in irrigation amount in the winter wheat field, residual nitrogen content decreased first followed by an increase. In contrast, residual nitrogen content in the maize field peaked in W1 treatment. The partial productivity of nitrogen fertilizer mirrored the yield of both crops. Water consumption of both crops increased with irrigation amount, yet their water use efficiency increased with irrigation amount initially and then declined when irrigation amount exceeded a threshold value. 【Conclusion】 Analysis of irrigation amount, yield and water use efficiency of the two crops indicates that the optimal irrigation amount and nitrogen fertilization for winter wheat and summer maize were 214 mm and 100 kg/hm2, and 103 mm and 100 kg/hm2 respectively. They can be used as an improved irrigation and fertilization for maize production in the studied region.