Nitrogen losses from food production in the North China Plain compared to environmental targets

Abstract

North China Plain (NCP) is a region in China, with highly intensive food production and a hotspot of nitrogen (N) losses to the environment. Region-specific N management is, therefore, required to effectively reduce agricultural N losses. For this it is important to identify the N flows and environmental targets in the food chain (including crop production, animal production, food processing, and human consumption) at the county scale. We developed an integrated assessment N framework. It combines a food chain approach with an air quality model and groundwater model. We apply this method to quantify the relative contributions from parts of the food chain to N losses. We identify environmental targets to air and water in Quzhou, a typical agricultural county in the NCP. We found that N losses to the environment from the food chain were ~11 kt  in Quzhou in 2017. Approximately 80% of this amount is from crop and animal production, which is primarily caused by the low N use efficiency in crop production (28%) and animal production (18%). Ammonia (NH3) emissions to air (4.1 kt N) and N leaching (2.1 kt N), and direct discharges of manure to water (1.9 kt N) are the main contributors to the N losses in Quzhou. To meet the environmental targets for air quality (PM2.5) and groundwater quality, the NH3 emissions and N leaching need to be reduced by 55%, and 21-50%, respectively. Our findings indicate that better nutrient management is urgently needed to reduce agricultural N losses and to support Agriculture Green Development in NCP.