摘要：Acting as a link and buffer between farmland and receiving waterway, drainage ditch reduces nitrogen (N) and phosphorus (P) levels in farmland drainage and control nonpoint source pollution. This study compares two ditches with augmenting plant density and a natural ditch. The geomorphology of three ditches was similar. Two different water levels of drainage ditches were compared to evaluate the nutrient mitigation capacities in different growth stages under low initial nutrient concentrations of the inflow. The results showed that ammonium-nitrogen (NH4-N), nitrate-nitrogen (NO3-N), and phosphate-phosphorus (PO4-P) removal efficiencies of the three experimental ditches increased from 0 to 5th day during the same growing season, but fluctuations in removal rates were observed. The NH4- N and PO4-P removal efficiencies were higher in the augmenting plant ditch than that in the natural ditch. A decreasing trend in removal efficiencies, from early to late growing seasons, was found. Efficiencies of NH4-N removal in the plant-augmented ditch with low water level were 94.2% ± 2.0%, 88.8% ± 2.0%, and 71.0% ± 4.1% at 5th day averagely during the early, middle, and late growing seasons, respectively. Similarly, the PO4-P removal efficiencies were 85.4% ± 3.0%, 69.0% ± 4.0%, and 54.9% ± 5.0%, respectively. However, under the water stagnant, the NH4-N and PO4-P efficiencies in the low-water-level ditch were higher than those in the high-water-level ditch when retention time was 5th day, except in the middle growing season. Therefore, the existing ditch management supports the mitigation of agricultural non-point source pollution in the Sanjiang Plain.
关键词：Agricultural non-point source pollution; Nitrogen;
Phosphorus; Water level; Retention time
