Abstract: This paper proposed a method of site-specific ecological ditch construction as an available technique for farmland non-point pollution control in Pearl River Delta. A typical paddy field system of Shangzhou Village located at Doumen District of Zhuhai City was selected as a case. The demonstration project was constructed by properly converting original farmland irrigation and drainage system to a well-designed wetland, and the control efficiency was evaluated. The results showed that the removal efficiency of suspended solid (SS), total phosphorus (TP), total nitrogen (TN), chemical oxygen demand (CODCr), NH+4-N, and biochemical oxygen demand after 5 days (BOD5) in the runoff of the paddy field system was 71.7%, 63.4%, 49.9%, 26.6%, 14.5%, and 11.6%, respectively, without harming inherent drainage function. The wetland system worked well in reducing nutrient and particulate pollutants, especially for TP and SS, but had no significant effects in reducing organic pollutants. The proposed method of site-specific ecological ditch construction was cost-effective, which reduced the pollution load of the runoff to adjacent water body and improved the farmland landscape, with definite demonstration value for controlling non-point source pollution in Pearl River Delta and in similar regions with developed economy, high population, and scarce land.

Key words: Quercus variablis, forest gap, seedling, architecture.