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The effects of water deficit on maize growth and physiological activities have been extensively studied. However, there are few studies about how various nitrogen (N) fertilizer types alleviate the impact of water stress on maize yield. A two-year field experiment was conducted to explore the effects of N type on maize growth, physiological characteristics and gain yield under various water-stressed conditions in 2019 and 2020. This experiment included three irrigation levels of W1 (60% ET c , ET c is crop evapotranspiration), W2 (80% ET c) and W3 (100% ET c), and three N fertilizer types of urea (U), slow-release nitrogen fertilizer (SRF) and blending U and SRF (UNS). The results showed that W1 and W2 significantly reduced maize leaf area index and leaf N content, which declined maize net photosynthetic rate (P n), transpiration rate (T r) and chlorophyll fluorescence, inhibited chlorophyll synthesis and thus reduced maize yield. W3 not only increased maize growth, P n and T r , but also enhanced the correlation between P n , chlorophyll content, chlorophyll fluorescence parameters and leaf area index/leaf N content. The application of UNS alleviated the grain yield reduction associated with water stress. Under W1 (W2), the grain yield in UNS were 3.6–22.1% (10.4–25.0%) and 4.4–24.2% (5.3–15.4%) greater than that in U and SRF, respectively. Although W3SRF obtained the highest yield grain among all the treatments, no significant difference was found between W3UNS and W3SRF. Under the same irrigation amount, UNS increased the water productivity compared with U. In conclusion, UNS could stabilize grain yield by regulating maize leaf functional traits to cope with future climate change and ensure regional food security. • LAI and leaf N content can evaluate the response of leaf development process to water deficit. • W3 increased the correlation coefficients between leaf function index and LAI/leaf N content. • UNS alleviated the negative effects of water deficit on leaf functional index of maize. • UNS could stabilize grain yield by regulating maize leaf functional traits. [ABSTRACT FROM AUTHOR]

Agricultural production is facing the risk of severe water shortage, serious non-point source pollution and low water productivity (WP) and nitrogen use efficiency (NUE). It is a major challenge to achieve environmentally friendly production of maize with high WP and NUE. A two-year field experiment with three irrigation levels of W1 (60% ET c , ET c is the crop evapotranspiration), W2 (80% ET c) and W3 (100% ET c), and three nitrogen (N) fertilizer types of urea (U), slow-release N fertilizer (SRF) and urea blended with slow-release N fertilizer (UNS) was conducted in 2019 and 2020, so as to quantify their impacts on the maize dry matter, N uptake and remobilization, grain yield, WP, NUE and residual soil NO 3 −-N. The results showed that W2 and W3 significantly increased total dry matter (8.0% and 14.7%), grain yield (19.4% and 33.0%), and NUE (1.5% and 2.2%) compared with W1. Total N uptake of maize declined by 23.2% and 9.6% under W1 and W2, leading to 11.9% and 5.8% increased of soil NO 3 −-N, respectively. Compared with U, UNS increased post-silking N uptake by 19.1%, thereby enhancing grain yield by 18.3%. Compared with SRF, UNS increased N remobilization from vegetative organs to grains by 15.0%, thereby resulting in 2.3% increase in grain yield. Under the same irrigation amount, UNS and SRF improved WP and NUE compared with U. W3SRF obtained the highest grain yield, with increases in grain yield by 2.4–58.8% compared with other treatments, while there was no significant difference between W3SRF and W3UNS. More importantly, UNS significantly increased grain yield and alleviated the impact of water stress on maize production under W1 and W2. In conclusion, UNS could stabilize grain yield under water-stressed conditions, while SRF could increase grain yield under full irrigation. • W3 (100% ET c) increased maize N uptake and significantly reduced residual soil NO 3 −-N. • UNS increased post-silking N uptake by 19.1%, resulting in 18.3% increases of grain yield. • UNS enhanced N remobilization of vegetative organs by 15.0% and thus grain yield by 2.3%. • UNS can alleviate the pressure of maize yield reduction caused by water deficit through adjust N supply. [ABSTRACT FROM AUTHOR]