Construction of Ecological Ditches for Agricultural Nitrogen and Phosphorus Interception in Zhejiang: Implications for Controlling Agricultural Non-point Source Pollution in China

The effective governance of agricultural non-point source pollution is essential for enhancing the agricultural ecological environment. It also promotes green sustainable agricultural development, and constructing rural ecological civilization in China. Recently, ecological ditches have been widely implemented to reduce nitrogen and phosphorus levels in agricultural runoff. This article systematically discusses the demand for controlling agricultural non-point source pollution in Zhejiang Province, the technical models and operational mechanisms of ecological interception ditches. In addition, it evaluates the effectiveness of these ditches in reducing nitrogen and phosphorus, and identifies the challenges encountered during their implementation. The results indicate that the ecological ditch system in Zhejiang Province achieves average interception rates for NH₄⁺-N, TN, TP, and COD in agricultural drainage water, ranging from 31.1%-85.1%, 16.6%-55.9%, 27.7%-66.9%, and 16.6%-57.3%, respectively. After purification, the water quality at the outlet of the ditches can be improved by 1.0-1.5 standard grades compared to that at the fields drainage outlets. Additionally, the installation of nitrogen and phosphorus interception facilities within the ditches can enhance the interception rate of pollutants in agricultural drainage by approximately 20%. Despite the significant role of interception in pollutant reduction, the construction and maintenance of ditches in Zhejiang Province still face challenges due to variations in pollution characteristics arising from different regional agricultural management practices and limited funding sources. In summary, this systematic overview of the construction and operation of ecological ditch systems in Zhejiang Province aims to provide technical references and model insights for the prevention and control of non-point source pollution in China.