It has been reported that 31% of the rivers and six of nine major coastal bays in China have suffered from eutrophication, caused by elevated concentrations of nitrogen (N) and phosphorus (P). In addition, > 60% of the monitored drinking water wells are severely contaminated, classified as level IV (I–V, where V is the worst) or worse.(1,2) Transfers of N and P from agriculture are the main contributors to the poor water quality.(2)

China has recently introduced water protection policies to address nutrient transfers to vulnerable watercourses, such as the 2015 Water-Pollution-Prevention-Control-Action -Plan. However, this policy focuses on the management of industrial effluents and includes only two mitigation strategies related to agriculture: (i) relocation of livestock farms outside the highly populated regions, and (ii) reduction of chemical fertilizer use to increase recycling of manure in crop production. These actions have been implemented without identifying the key regions that are vulnerable for NO₃^– and P leaching from agriculture to groundwater and surface waters. As a result, such policies may not have the desired effect in reducing N and P contamination in waters.