Effects of cutting aquatic plants on nitrogen and phosphorusinterception in ecological ditches

In this study, Canna glauca, Hydrocotyle vulgaris, Sparganium stoloniferum, Myriophyllum spicatum and Juncus effusus aquatic plants were planted in an ecological ditch. The effects of plant cutting management on nitrogen (N) and phosphorus (P) interception in ecological ditches were then analyzed by N and P content comparisons and removal rates in water samples. The results showed that the amounts of total N and P removed by cutting aquatic plants in September and November were 11.889 kg and 1.099 kg, respectively, in the 300 m2 ecological ditch. Total N uptake by different aquatic plants was in the order of C. glauca (7.686 kg) > M. spicatum (1.501 kg) > H. vulgaris (1.128 kg) > J. effusus (0.974 kg) > S. stoloniferum (0.601 kg). The order for total P was C. glauca (0.433 kg) > M. spicatum (0.233 kg) > S. stoloniferum (0.191 kg) > H. vulgaris (0.134 kg) > J. effusus (0.109 kg). Cutting plants also improved N and P removal efficiency in ditch sediments, except for S. stoloniferum. Compared to non-cutting areas, cutting areas showed increased sediment total N nutrient removal rates with M. spicatum (20.73%) > H. vulgaris (20.00%) > J. ef-fusus (16.05%) > C. glauca (4.86%) > S. stoloniferum ( 9.72%). That for total P was J. effusus (20.69%) > H. vulgaris (16.67%) > C. glauca (4.55%) > M. spicatum (0.00%) > S. stoloniferum ( 16.00%). N and P removal rates in water also increased under cutting treatment. Thus cutting aquatic plants not only removed nutrients from ditch systems, but also increased N and P interception in water and ditch sediments.