Nutrient imbalances in China with the focus on N and P in agricultural systems in Jiangsu Province

During recent decades, the use of mineral fertilisers, especially nitrogen (N), has increased significantly in China compared with the use of organic fertilisers, such as crop residues and human, animal and green manure. At the same time, an ever increasing population is putting pressure on the agricultural sector due to their increased demand for food and is competing for arable land due to a rapid, ongoing urbanisation and industrial expansion. China now faces serious environmental problems, such as eutrophication and degradation of drinking water quality due to heavy loads of polluted, untreated wastewater from households and industry and losses of excessive fertiliser N from farmland. This report reviews the nutrient imbalances in Chinese agriculture, especially in Jiangsu Province. The process-based simulation model GLEAMS was used to estimate the N and phosphorous (P) losses and transformations in an intensive vegetable-producing peri-urban area in Shiba Village, Nanjing City, Jiangsu Province. The results showed that currently, there is an enormous surplus of N in the system, resulting in high losses of N by leaching and denitrification and very low nutrient use efficiency. According to the simulation results, the nutrient use efficiency may be improved and the losses of N significantly reduced by decreasing the fertiliser input to twice the nutrient yield in the harvest, without any loss in crop yield