Research Advances on Process and Monitoring Methods of Nitrogen and Phosphorus Loss in Paddy Fields

Rice is one of the major cereal crops in China. During the rice production process, part of the nitrogen and phosphorus in the soil and fertilizer migrates to the surrounding water body through leaching and runoff in the form of solutes or particles, causing groundwater pollution and eutrophication of water bodies. Ammonia produced by ammonium volatilization in paddy soil and nitric oxide produced by denitrification reactions enter the atmosphere, aggravating the greenhouse effect. The commonly used monitoring methods of gas volatilization, runoff, and leaching in paddy fields from domestic and international studies are introduced, and the monitoring indicators, monitoring frequency, and monitoring depth in the pathways are further discussed; the main nitrogen and phosphorus forms in runoff loss and leaching loss are summarized; the monitoring frequency is determined by the characteristics of runoff and the fertilization; plant absorption and depth of groundwater should be considered to determine the depth of leaching monitoring. This study provides a reference for further monitoring of nitrogen and phosphorus losses in paddy fields.