The North China Plain (NCP) is a major food producing region in China. Overexploitation of groundwater for irrigation and overapplication of nitrogen (N) fertilizer have contributed to increased food production but have also resulted in water shortages and groundwater contamination. This paper reviews potential conflicts between strategies that ensure water security, food security, and water pollution reduction in the NCP. It outlines some agriculture-related strategies for resolving water shortages. Besides water saving and N saving technologies, policies such as fallow tillage, a water transfer project accounting for the recovery of groundwater level, and N management limiting N input in farmland are discussed. In particular, there are conflicts between the strategies for recovering shallow groundwater and releasing N from the unsaturated zone to the aquifer in the piedmont plain because a large amount of N is stored in the thick unsaturated zone. A transition from food-oriented strategies to sustainable development management of resources and the environment is necessary. To benefit from synergies and avoid tradeoffs between water security, food security, and clean water in the NCP, we must combine water and N management, groundwater level and water quantity control, socioeconomic issues, and climate change.

Rice production not only consumes large amounts of irrigation water and fertilizer, but also poses a high risk of water pollution by delivering nitrogen (N) through surface runoff. To ensure sustainable rice production, many water-saving irrigation managements have been proposed and implemented, but drainage water managements receive far less attention and need to be further explored. This study aimed to determine the paddy drainage optimization management and assess its potential to water and food security in China via different scale methods (from pot and field experiments to national assessment). The national investigation of water and N fertilizer use in paddy fields implied that diffuse N pollution was expected to continue increasing, especially in the Yangtze river basin. Two-years field experiments at typical sites identified that the tillering and jointing–booting stages were critical risk stages for N runoff loss, and pot experiments on the critical stages were conducted to determine the optimal drainage water level without yield reduction. Then, the applicability of paddy drainage optimization was verified and evaluated by drainage optimization field experiment and precipitation characteristics analysis. Finally, the potential of drainage optimization on mitigating N runoff loss was estimated by scenario analysis at the national scale. After implementing paddy drainage optimization in field experiments, surface runoff and nitrogen runoff loss decreased by 27.97–78.94% and 35.17–67.95%, respectively, without affecting rice yield. By full implementation of the optimal drainage and fertilization management, N runoff loss could be reduced by 0.19 Tg yr⁻¹ at the national scale. These results suggest that paddy drainage optimization is an agro-ecosystems friendly water management for sustainable rice production, and has notable potential to ensure water and food security in China.

Soybean import accounts for 90% of China's total domestic soybean supply. Such import has a substantial impact on how the country's resources are used as well as on its environment. In this study, we performed a national-scale assessment of the impact of soybean import on domestic cropland conversion, crop production, water use and nitrogen (N) fertilizer application. Results show that soybean production in China decreased by 26% (4.46 million tons) and sown areas were reduced by 25% (2.39 million ha) from the peak of 2004 to 2016. Of the areas taken out of the soybean production, 70% were converted to maize, 20% to rice, 3% to vegetables and 7% to fruits during this period. As a result of the cropland conversion, the production of maize, rice, vegetables and fruits increased by 10.42, 3.34, 2.49 and 3.26 million tons respectively. However, irrigation water use in the areas that were converted to the cultivation of the four types of crops increased by 96.42% (3.05 km³), with much of it coming from northern provinces where water is generally scarce. The application of N fertilizer increased by 256.65 thousand tons (almost 5 times) on the converted areas, partly due to the loss of the N-fixing soybean cultivation. Although a large quantity of virtual water and land were imported through soybean trade, the water use and N application were increased in reality. The analysis of the land-water-food-environment nexus in the context of soybean import provides comprehensive and useful information about the benefits and trade-offs associated with China's international soybean trade.

The estimated, effective increase of agricultural fertilizer applied in China by 10.57 Mts from 2006 to 2016 is a crucial factor affecting the water environment. Based on analyzing the nitrate-leaching rate, the nitrogen-fertilizer application rate, and crop yield in wheat and maize key cultivation divisions in China, this paper applied the grey water footprint analytical method to estimate THE grey water footprint and its proportion to total water footprint and analyzed the spatial differences from 2012 to 2016. Results showed that the grey water footprint of wheat was higher in North and Northwest China with an increasing trend, while that of maize was higher in Southwest and Northwest China because of high nitrogen application rates and low yields in these regions. Except for the Southwestern division, wheat’s grey water footprint was about 1.3 times higher than the blue water footprint, while, for maize, it was two to three times higher. When analyzing and planning water demand for crop irrigation, the water required for nonpoint source pollution due to chemical fertilizers should be considered. Focusing blue water (irrigation) alone, while neglecting green water and ignoring grey water footprints, it might lead to overestimation of available agricultural water resources and failure to meet the goals of sustainable use of water resources.

Water-Energy-Food (WEF) Nexus and CO₂ emissions for a farm in northwest Iran were analyzed to provide data support for decision-makers formulating national strategies in response to climate change. In the analysis, input–output energy in the production of seven crop species (alfalfa, barley, silage corn, potato, rapeseed, sugar beet, and wheat) was determined using six indicators, water, and energy consumption, mass productivity, and economic productivity. WEF Nexus index (WEFNI), calculated based on these indicators, showed the highest (best) value for silage corn and the lowest for potato. Nitrogen fertilizer and diesel fuel with an average of 36.8% and 30.6% of total input energy were the greatest contributors to energy demand. Because of the direct relationship between energy consumption and CO₂ emissions, potato cropping, with the highest energy consumption, had the highest CO₂ emissions with a value of 5166 kg CO₂eq ha⁻¹. A comparison of energy inputs and CO₂ emissions revealed a direct relationship between input energy and global warming potential. A 1 MJ increase in input energy increased CO₂ emissions by 0.047, 0.049, 0.047, 0.054, 0.046, 0.046, and 0.047 kg ha⁻¹ for alfalfa, barley, silage corn, potato, rapeseed, sugar beet, and wheat, respectively. Optimization assessments to identify the optimal cultivation pattern, with emphasis on maximized WEFNI and minimized CO₂ emissions, showed that barley, rapeseed, silage corn, and wheat performed best under the conditions studied.

Rising human demand and climatic variability have created greater uncertainty regarding global food trade and its effects on the food security of nations. To reduce reliance on imported food, many countries have focused on increasing their domestic food production in recent years. With clear goals for the complete self-sufficiency of rice production, Sri Lanka provides an ideal case study for examining the projected growth in domestic rice supply, how this compares to future national demand, and what the associated impacts from water and fertilizer demands may be. Using national rice statistics and estimates of intensification, this study finds that improvements in rice production can feed 25.3 million Sri Lankans (compared to a projected population of 23.8 million people) by 2050. However, to achieve this growth, consumptive water use and nitrogen fertilizer application may need to increase by as much as 69 and 23 %, respectively. This assessment demonstrates that targets for maintaining self-sufficiency should better incorporate avenues for improving resource use efficiency.