NITROGEN ASSIMILATION BY RIPARIAN BUFFER SYSTEMS RECEIVING SWINE LAGOON WASTEWATER

A three-year study was conducted to determine the feasibility of using riparian buffer systems to assimilate nitrogen (N) from swine lagoon effluent. Replicated 30 ×4 m plots were established at the interface of a pasture and riparian forest. Wastewater from the third lagoon of the University of Georgia Coastal Plain Experiment Station main swine research unit was applied to each plot by overland flow from tanks at the top end of each plot. The wastewater, which contained an average N concentration of 160 mg L–1 N, primarily as ammonium (NH4-N), was applied to the plots at two different rates (either once per week [1 ×, 1285 L/plot] or twice per week [2 ×, 2570 L/plot]). Three different vegetative buffer treatments were evaluated: (1) 10 m grass buffer draining into 20 m existing riparian zone vegetation; (2) 20 m grass buffer draining into 10 m existing riparian zone vegetation; and (3) 10 m grass buffer draining into 20 m maidencane (Panicum hematomon). The effects of the wastewater on surface runoff and groundwater quality were evaluated by transects of surface runoff collectors, suction lysimeters, and shallow groundwater wells which extended from the top to the bottom of each plot. Data analyses showed differences due to wastewater application rate and distance downslope from the wastewater application pipe. Nitrogen concentrations increased over time at the top ends of the plots but showed little increase at the bottom ends of the plots. Overall, all three vegetative treatments were successful in assimilating N from the wastewater. The study showed that riparian buffer systems, where wastewater is applied by overland flow, can be effective in assimilating N contained within lagooned animal wastes.