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The integrated management of water and fertilizer has been widely applied for effectively utilizing limited rainwater resources in rainfed farming systems. However, the combined effect of straw mulching and urea blended with slow-release nitrogen fertilizer (SU) on rainfed maize has seldom been studied. A two-year field experiment (2016–2017) was conducted to evaluate the effects of various agronomic practices, i.e. wheat straw mulching over the entire soil surface (QSU), wheat straw mulching over the partial soil surface (DSU), and water-retaining agent (BSU) under two N application rates (N1: 120 kg ha−1 and N2: 180 kg ha−1) on rainfed maize in northwest China. The results showed that DSUN2 delayed leaf senescence, increased chlorophyll content and photosynthesis, promoted N uptake, and increased grain yield (GY) (by 19.34%-39.91% in 2016 and 11.00%-52.57% in 2017), water use efficiency (WUE) (by 14.35%-56.21% in 2016 and 8.87%-57.44% in 2017) and nitrogen use efficiency (NUE) (by 12.03%-31.82% in 2016 and 0.49%-9.34% in 2017). More soil water was retained by QSU, which significantly promoted maize growth, but decreased GY compared with DSU. In conclusion, DSUN2 was the most effective agricultural management practice for improving GY, WUE and NUE of rained maize in northwest China. [ABSTRACT FROM AUTHOR]

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]

Optimising the management of water and fertilizer, and fully exploiting the positive effects of the coupling of water and fertilizer, are important ways of achieving high crop yields and promoting the sustainable development of water-efficient agriculture. The objective of this study was to investigate the coupling effects of different irrigation levels and different mixing ratios of slow-release nitrogen fertilizers on the physiological growth characteristics and yield of winter wheat in Guanzhong region under drip irrigation. In this study, field experiments were conducted in two winter wheat growing seasons, 2018–2019 and 2019–2020. The study included three irrigation levels: W1 (60% ETc, where ETc is the evapotranspiration of the crop), W2 (80% ETc), and W3 (100% ETc); and four N fertilizer treatments: U (100% urea), UNS1 (urea: slow-release N fertilizer = 1:1), UNS2 (urea: slow-release N fertilizer = 1:3) and SRF (100% slow-release N fertilizer). Compared to W1 and W2, W3 prolonged the winter wheat leaf functional period, increased leaf area index and net photosynthetic rate (P n), and promoted dry matter accumulation. The total N content of winter wheat decreased by 22.67% and 9.93% under W1 and W2 conditions, respectively. The nitrogen use efficiency (NUE) decreased by 5.87% and 1.97%, respectively, leading to a decrease in yield. Slow-release nitrogen fertilizer (SRF) and its mixture treatments (UNS1, UNS2) increased post-flowering nitrogen uptake in winter wheat compared to U. At the same irrigation level, water use efficiency (WUE) was increased by 34.03%, 13.35%, and 20.86% in the UNS2 treatment compared to U, UNS1, and SRF, respectively. W3UNS2 obtained the highest grain yield: 8026.32 kg hm−2 (2018–2019) and 8993.25 (2019–2020) kg hm−2, with a 9.85–68.24% yield increase compared to other treatments. Und4er the treatments of this study, yield, WUE, and NUE of winter wheat reached 90% of the maximum at irrigation levels of 82.04–91.83% ETc and 59.18–83.67% of slow-release N fertilizer in blended fertilizer. Under water stress conditions, UNS1 and UNS2 can mitigate the effects of water deficit on plant growth and stabilize grain yield. This study provides useful information for optimising water and nitrogen management decisions for winter wheat in semi-arid climatic regions, and contributes to the promotion of sustainable development of wheat production and water-efficient agriculture. • The two-year drip trial was conducted in a sheltered canopy in GuanZhong. • Field trial address in the coupling impacts of irrigation&fertilizer on winter wheat. • Recommended irrigation volumes and mixing ratios were obtained using modelling. • Blended slow-release nitrogen fertilizer can effectively mitigate the drought effects. • 100% ETc with U:SRF = 1:3 is the most recommended irrigation and fertilization option. [ABSTRACT FROM AUTHOR]