Eutrophication is a serious problem in Chinese rivers and seas, largely caused by increased nitrogen (N) and phosphorus (P) losses from agriculture. Chinese agriculture is known to be nutrient inefficient. Previous studies showed that fertiliser use can be reduced while increasing yields in the so-called Double High Agriculture (DHA) program. We simulated the effects of improved nutrient management on N and P export by rivers in China in 2050 and the associated coastal eutrophication using the Global Nutrient Export from WaterSheds 2 (NEWS 2) model. Four scenarios were developed: (1) improved practice (IP), assuming an approximate 20% decrease in synthetic fertiliser use and a 15% increase in crop yields relative to a reference scenario; (2) integrated soil-crop systems management (ISSM), assuming a 30% decrease in synthetic fertilisers and a 30% increase in crop yields; (3) IP-MR, with assumptions as for the IP scenario as well as efficient manure recycling (MR); and (4) ISSM-MR, with assumptions as for the ISSM scenario in addition to efficient MR. The results indicate that reducing inputs of synthetic fertilisers alone (IP and ISSM scenarios) may reduce river export of N and P by <15%. The scenarios also accounting for improved manure management (MR) are more effective, and reduce N and P inputs to rivers by 10-35%.
- algal blooms
- environmental modelling
- integrated nutrient management
- river flow