The food security risks in the Yangtze River Delta of China associated with water scarcity, grain production, and grain trade.

Grain production consumes a large amount of water and is affected by the degree of water scarcity and participation in the grain trade in various regions. The grain trade has changed the food security risks in regions where grain exports and imports. Therefore, it is crucial to consider regional water scarcity to understand food security risks from the grain trade network. Here, we construct a new framework for measuring regional food security risks associated with water scarcity, grain production, and grain trade based on a cross-city grain trade network combined with virtual water flows to evaluate the regional food security risks in the Yangtze River Delta region (YRD) of China in 2017. The results show that under the current domestic grain trade pattern in China, the YRD and its four provincial-level administrative regions are in a net grain import state. The grain trade within the YRD is concentrated in exports from the two major grain-producing areas of Anhui and Jiangsu to Zhejiang and Shanghai, especially from northern Jiangsu to southeastern Zhejiang. The net import results of virtual blue water in most cities indicate that the YRD has shifted its water resource pressure to other grain exporting regions in China, with Shanghai and Zhejiang being the greatest beneficiaries. Extreme risk only exists in Shanghai, and severe and moderate risks are concentrated in Jiangsu. The current grain trade has reduced the overall food security risk in the YRD by 1.3 % but increased the risks in Shanghai and Zhejiang by 2.1 % and 0.8 % respectively. This study highlights the potential risks that excessive production of food in water-scarce areas in the grain trade system may bring to a stable food supply, providing useful information for a comprehensive understanding of the food and water security situation and for future trade-offs.

The potential capability of substituting chemical fertilizers with crop straw and human-livestock-poultry manure in areas with different topographic characteristics.

Agricultural production and lifestyle are constrained by topography, causing notable under disparities in the composition, distribution, and environmental benefits of crop straw and human-livestock-poultry manure (CSHLPM) in areas with different topographic characteristics. Under the premise of the international consensus on sustainable development, it has become an objective requirement to improve the use of CSHLPM as fertilizer, and minimize the use of chemical fertilizers. Thus, an investigation was conducted to assess the difference in the quantity and composition of CSHLPM in plain, hill, and mountainous areas, taking Anhui Province of China as a case study, to evaluate the potential contribution of CSHLPM to farmland and identify the environmental benefits. The results show that the composition of CSHLPM in plain, hill, and mountainous areas varied greatly, and the reuse of CSHLPM in farmland could supplement, but not completely replace the use of chemical fertilizer to meet the needs of nutrients. In plain areas, CSHLPM did not provide the necessary amount of N and P2O5 for crop growth, whereas in mountainous areas, P2O5 was not available in adequate amounts for crop growth. Only in hilly areas can CSHLPM be used to completely replace chemical fertilizers and supply the necessary amounts of nutrients for crop growth. Based on the characteristics of different topographies, two constructive suggestions for improving the management strategy of CSHLPM were put forward: adjust the industrial structure of husbandry and planting, and specify the recommended ratios for mixing organic chemical fertilizers.