Research of Ditch Interception Effect of Nitrogen and Phosphorus of Pontederia Cordata

Through planting the ornamental plant Pontederia cordata in the ditch, the effect of interception and purification water of Pontederia cordata ditch (eco-ditch) and without plant ditch (natural ditch) was studied at different times, and studied seasonal change of the contents of aboveground nitrogen, phosphorus and biomass of Pontederia cordata. The results showed that eco-ditch and natural ditch could purify nitrogen and phosphorus contents of water, and reduction range(3.37%-33.33%)of total nitrogen and total phosphorus was higher than reduction range(-3.66%-7.14%) of nitrate and ammonium nitrogen, the interception capacity of eco- ditch(6.82%- 33.33%)was obviously higher than natural purification of natural ditch(-3.66%-16.67%). After raining the content of total nitrogen and nitrate nitrogen in ditch water had the tendency of increasing firstly and then declining, while the content of ammonium nitrogen was unstable, the content of total phosphorus reached highest values after raining the 2nd, then tended to steadily. Seasonal dynamics of the contents of aboveground nitrogen, phosphorus and biomass of Pontederia cordata reached highest values in October, so, it was the best time to harvest. The content of the aboveground nitrogen, phosphorus was 28.38 g/ kg and 4.10g/kg and biomass was 0.19kg/m2. The harvest of Pontederia cordata would remove 5.36g/m2 of nitrogen and 0.78g/m2 of phosphorus every year, the objective is to provide the theory basis for restoration application of the development ornamental plant in ditch.