The Process and Factors of Nitrogen and Phosphorus Loss from Farmland and Transport in Ditch

The irrational application of nitrogen and phosphorus in farmland ecosystems leads to a surplus of nitrogen and phosphorus in farmland, which is lost through runoff and transported by ditches and rivers into receiving water bodies. Ultimately, this causes environmental problems such as the eutrophication of water bodies. The critical processes involved in the transport of nitrogen and phosphorus from agricultural land to surface water bodies include the loss of agricultural nitrogen and phosphorus to ditches and the transport and transformation processes in ditches. This paper summarises the main advances in agricultural nitrogen and phosphorus transport in ditches through literature research in terms of three aspects: the processes and factors of nitrogen and phosphorus loss from agricultural land to ditches, the transport process and factors of nitrogen and phosphorus in ditch and methods for assessing nitrogen and phosphorus removal from ditches. Previous watershed assessment studies were mostly from the perspective of hydrology, temperature, light and stream morphology, with insufficient consideration given to the impact of biological factors on nitrogen and phosphorus transport from ditches. Studies on biological factors have focused on the removal effects of ecological ditches, with less research on the mechanisms by which biological factors influence nitrogen and phosphorus attenuation in ditches and on the spatial and temporal characteristics of ditch biological conditions at the watershed scale. In the future, an integrated assessment approach to should be used to quantify the role of biological conditions in ditch transport. This research contributes to a deeper understanding of the formation of non-point source pollution in farmland, providing valuable insights for calculating pollution loads and protecting water environments related to agricultural non-point source pollution.