Increasing nitrogen use efficiency in agriculture reduces future coastal water pollution in China

Maryna Strokal1,2, Carolien Kroeze2, Mengru Wang2,3, Ang Li2,3, Lin Ma3

1 Environmental Systems Analysis Group, Wageningen University, Droevendaalsesteeg 3, 6708 PB Wageningen, The Netherlands, https://www.wageningenur.nl/en/Persons/Maryna-M-Maryna-Strokal.htm?subpage=projects, [email protected] 

2 Water Systems and Global Change Group, Wageningen University, Droevendaalsesteeg 3, 6708 PB Wageningen, The Netherlands

3 Key Laboratory of Agricultural Water Resource, Center for Agricultural Resources Research, Institute of Genetic and Developmental Biology, Chinese Academy of Sciences, Huaizhong Road 286, Shijiazhuang, Hebei 050021, China

Abstract

Chinese agriculture has been industrializing since the 1990s to produce enough food. This increased nitrogen (N) in Chinese rivers and coastal waters, resulting in eutrophication-related problems. We analysed three options to reduce future N pollution of coastal waters in China by 2050. We did it using the MARINA Nutrient model (a Model to Assess River Inputs of Nutrients to seAs). Two optimistic scenarios (OPT-1 and OPT-2) were developed, taking the Global Orchestration scenario (GO) of the Millennium Ecosystem Assessment as a baseline. These scenarios assume efficient N management in agriculture (OPT-1 and OPT-2) and sewage (OPT-2). We also assessed effects of the “Zero growth in fertilizer use after 2020” policy (the CP scenario). Results show that N management in agriculture is more effective to reduce future N pollution of coastal waters than N management of sewage. In GO, Chinese rivers are projected to export 38-56% more N in 2050 than in 2000 because of poor manure management. The current policy in agriculture (CP) may not be successful to reduce coastal water pollution. In contrast, our more optimistic scenarios project much lower river export of N in 2050 (at around levels of 1970 for northern rivers and 2000 levels for central and southern rivers). This is mainly because OPT-1 assumes high rates of manure recycling, leading to decreased use of synthetic fertilizers. Improved sewage management in OPT-2 can further reduce N export by northern rivers. Our results can serve as a basis for decision makers on N management.