Exploring the coupling characteristics of regional water resources and food security helps to promote the sustainable development of grain production and is of great significance for achieving global food security. From the aspects of regional “water supply”, “water use” and “water demand”, the coupling characteristics of water resources and food security were systematically revealed; the new challenges faced by regional food security from the perspective of water resources were clarified; and effective ways to promote the utilization of regional water resources and the sustainable development of grain production were explored. This paper took Northwest China, which is the most arid region, where water-resource utilization and food security are in contradiction, as the research area. The water-resource load index, the water footprint of grain production and the water-consumption footprint were used to quantify the regional water-resource pressure index, as well as the residential grain-consumption types, population urbanization, the industrial-grain-processing industry and their corresponding water-consumption footprints from 2000 to 2020. The coupling characteristics of water resources and food security were systematically revealed. The results showed the following: (1) In 2000–2020, the water-resource load index increased from 4.0 to 10.7, and the load level increased from III to I. At the same time, agricultural water resources were largely allocated elsewhere. (2) During the period, the food rations showed a significant decreasing trend, and the average annual reduction was 3.4% (p < 0.01). The water footprint of animal products increased, particularly for beef and poultry (the average annual growth rates were 9.9% and 6.3%, respectively). In addition, the water footprint of industrial food consumption increased by 297.1%. (3) With the improvement of the urbanization level, the water-consumption footprint increased by 85.9%. It is expected that the water footprint of grain consumption will increase by 39.4% and 52.3% by 2030 and 2040, respectively. Exploring how to take effective measures to reduce the water footprint to meet food-security needs is imperative. This study proposed measures to improve the utilization efficiency of blue and green water and reduce gray water and the grain-consumption water footprint from the aspects of regional planting-structure optimization potential, water-saving irrigation technology, dietary-structure transformation and virtual water trade; these measures could better relieve the water-resource pressure and promote the sustainable development of grain production and water-resource utilization.

It is of great significance to systematically analyze the characteristics of the regional grain supply and demand balance, reveal the influence mechanism of crop sustainable development, and put forward effective countermeasures to achieve the goal of food security. This paper aims at addressing the unique geographical characteristics of Northwest China and the current lack of research on its food security. This paper systematically analyzes the temporal and spatial variation characteristics of the regional grain production, consumption and food security level. The main factors affecting regional food security are examined, and we put forward effective suggestions to promote regional sustainable production. The results show that the average annual growth rate of grain production in Northwest China from 2000 to 2021 was 3.4%, and the years of increased grain production accounted for 77.3%. The main reason for the increase in grain production was the increase in yield per unit area (average annual growth of 2.8%), of which the rice yield was the largest, up to 7.3 t/ha. Maize and wheat accounted for 60.7% and 23.4% of the total grain production in the region, respectively. From the perspective of the regional structure, Inner Mongolia contributed the most to the grain production in the region, accounting for 33.5% of the total output. Xinjiang, Shanxi, Shaanxi, Gansu, Ningxia and Qinghai contributed 17.1%, 15.4%, 15.2%, 13.0%, 4.5% and 1.3%, respectively, to grain production. From the perspective of the dietary structure, the grain consumption pattern in Northwest China has gradually changed from raw grains to animal products, which has undoubtedly increased the regional demand for grain. At present, since the increase in output is greater than the demand for food, the food self-sufficiency rate in the region has increased from 0.81 to 1.28. Since the grain yield per unit area in Xinjiang and Ningxia has a relative advantage over other provinces, to achieve regional food security for a long time, moderately increasing the grain planting area in these two provinces will help to promote regional food security. In addition, as the grains produced in the region are mainly wheat and corn, the yield level of wheat and corn in Xinjiang and Qinghai has a comparative advantage within Northwest China. Therefore, moderately increasing the planting area of wheat and corn in Xinjiang and Qinghai is of great significance in ensuring regional food security. The research results can provide theoretical support for the realization of regional food security and provide a reference for other regions in the world, to better serve global food security.

Knowledge of the characteristics of N₂O emissions and the influential mechanism is of great significance to mitigate greenhouse gas emissions in semi-arid areas. In the present study, a three-year water-control study was conducted; three simulated rainfall amounts (heavy, normal, and light rainfall = 275, 200, and 125 mm, respectively), two wheat (Triticum aestivum L.) planting modes (RF (ridge–furrow mulching system) and TF (traditional flat planting)) and four supplementary irrigation amounts (150, 75, 37.5, and 0 mm) were set up. The effects of different cultivation methods and irrigation amounts on soil N₂O emissions, the soil water content, available nitrogen content, and denitrifying enzyme activity were investigated to clarify the N₂O emission mechanism in winter wheat fields (Triticum aestivum L.). The results obtained after three years showed that compared with TF, the N₂O emissions under RF decreased by 21.62–30.72% (p < 0.001), whereas the soil water content increased by 6.26–8.82%, the available nitrogen content decreased by 1.71–16.24%, and the denitrifying enzyme activities increased by 0.2–24.16% under heavy rainfall conditions. Under conditions with normal and light rainfall, the N₂O emission fluxes under RF increased by 3.66–12.46% and 6.08–15.57% (p > 0.05), while the soil water contents increased by 6.13–11.49% and 8.05–13.88%, the soil available nitrogen contents decreased by 11.0–21.42% and 19.93–34.44%, and the denitrifying enzyme activities increased by 0.01–24.08% and 0.03–20.79% compared with TF. Principal component analysis showed that the main factors related to N₂O emissions under RF were the soil moisture content and available nitrogen content; these factors combined explained 94.37% the variation of the N₂O emissions. However, the main factors under TF were the soil moisture content and denitrifying enzyme activity; these factors combined explained 85.81%. In the heavy and normal rainfall years, compared with TF, using RF and 75 mm irrigation achieved the goal of reducing water usage as well as decreasing the N₂O emissions (or N₂O increase was not significant). In light rainfall years, RF with 150 mm irrigation obtained significant reductions in water usage compared with TF but it also increased the N₂O emission flux. Under different rainfall years, the yield of RF increased by 2.89–50.44% compared with the TF system, and the increase in wheat grain yield increased with decreasing rainfall.

Optimizing field cropping practices to improve nitrogen use efficiency is imperative to promote intensive and sustainable wheat production. As a cultivation method commonly adopted in arid and semi-arid regions globally, the ridge–furrow mulching system (RFMS) is capable of efficiently harvesting rainfall, reduce evaporation losses, enhancing soil moisture levels in the root zone, and boosting crop productivity. However, the combined effects of varying ridge–furrow ratios (RD), ridge heights (RH), and nitrogen application rates (RN) on nitrogen fertilizer bias productivity (PFPN) under the influence of climatic conditions, soil types, and field management practices remain poorly understood due to a lack of systematic evaluation. This study conducted a meta-analysis of 462 comparative datasets from 98 research projects to reveal the interactive effects of RFMS and nitrogen fertilizer across climatic gradients. The results showed that RH, RD, and RN increased by 23.78%, 22.37%, and 23.07% respectively (p < 0.05), with the most significant enhancement of PFPN being demonstrated by RH. The most significant improvement in PFPN was observed when RD = 1:1, R < 10 cm, and RN > 200 kg∙hm⁻², with PFPN increasing by 27.7%, 29.50%, and 29.32% respectively (p < 0.05). Climatic and soil physico-chemical factors and field management practices are the key factors influencing the RFMS. When average annual evapotranspiration (AE) < 1000, RN > 200 has the best effect on nitrogen utilization efficiency, while under the condition of AE > 1500, RN < 100 is more effective. In terms of mulching strategy, full mulching of ridges and furrows is recommended in areas with severe drought and low temperatures, while mulching only ridges or furrows is more appropriate in areas with relatively mild climate. The present study provides a scientific basis for the optimal design of ridge–furrow mulching configuration and nitrogen application level. This is achieved by considering climatic conditions, soil fertility, and field management in agro-ecosystems in arid and semi-arid areas.