Effects of vegetation on ammonium removal and nitrous oxide emissions from pilot-scale drainage ditches

Recently, vegetated drainage ditches have been used as one of the best management practices for controlling the transport of agricultural pollutants. In this study, a pilot-scale field experiment within a 135-km(2) agricultural catchment was conducted to investigate the effectiveness of ditches vegetated with Pontederia cordata (Pontederia) and Myriophyllum elatinoides (Myriophyllum) and ditches without vegetation (Control) on ammonium (NH4+-N) removal and nitrous oxide (N2O) emissions. Compared to the control treatment, the ditches with both plant species (P. cordata and M. elatinoides) increased NH4+-N removal rates by 50.8% and 71.4% and decreased N2O emissions by 68.3% and 70.4% for NH4+-N loadings of 25 mgL(-1) and 70 mgL(-1), respectively. The linear mixed-effect model revealed that effluent NH4+-N concentrations were significantly decreased by 2.54% and 2.10% for each increase of one unit on sediment NH4+-N sorption and plant TN accumulations (p < 0.0001). The dominant NH4+-N removal pathways in Myriophyllum ditch were plant uptake and microbial nitrification-denitrification. However, in Pontederia and control ditches, NH4+-N was mainly removed by sediment sorption. These findings may suggest that vegetated drainage ditches (e.g., M. elatinoides) are capable of removing NH4+-N from agricultural runoff and can additionally reduce N2O emissions. (C) 2016 Elsevier B.V. All rights reserved.