Abstract: Rice field wetland system is the main land use type in the high product agricultural watersheds of Southerneast China. Field experiments show that rice fields, ditches and multipond systems can effectively retain nonpoint phosphorus(P) and nitrogen (N) pollution from different land uses in a subwatershed of Chaohu Lake. The mechanisms of Pand Ntransfers and runoff losses from rice fields are mainly studied. By the analysis of Pand Ndynamics in rice fields, it was found that Pand Nloads in runoff were depended on field water level, applied fertilizer amount, precipitation, rice growth process, and height of field overflow mouth. Asimple model was built to calculate the quantity of Pand Nloads in runoff from rice fields. It shows that the total loads can reach 0.69 and 11.2kg·hm^-2 for Pand Nrespectively under the condition of applying fertilizers, which is the potential effect on Chaohu Lake eutrophication.

Key words: Phosphorus, Nitrogen, Rice fields, Model, Nonpoint pollution, big data, ecological environment, ecological network, climate change, air pollution