Simulation Experiment on the Effectiveness of Tree and Pasture Filter Strips to Remove NO3-N in Lateral Soil Water Flow

The impact of vegetative filter strips to reduce the delivery of nonpoint source pollutants from agricultural land to inland water systems is now recognized as an important element in overall agro-ecosystem management. A glasshouse experiment was undertaken to measure the effectiveness of tree (Eucalyptus camaldulensis Dehnh. and Casuarina cunninghamiana Mq.) and pasture filter strips to intercept lateral movement of NO3-N in soil water. Tree treatments retained significantly more NO3-N associated with shallow soil water movement (between the A and B soil horizons) than bare ground. Nitrate-N removal was not significantly different between trees and pasture, and among the tree treatments. However, uptake and accumulation of NO3-N by pastures was significantly (P < 0.001) greater than the trees. The average rates of N accumulation were 0.82 g m-2 and 1.52 g m-2 wk-1 for the tree plots and the pasture plots, respectively. The experiment also showed that the efficiency of NO3-N removal from soil solutions by trees was greater when NO3-N concentrations were relatively higher in the soil (81.4% removal at 20 mg L-1 compared to 68.1% at 10 mg L-1).