NITROGEN ASSIMILATION BY RIPARIAN BUFFER SYSTEMS RECEIVING SWINE LAGOON WASTE-WATER

A three-year study was conducted to determine the feasibility of using riparian buffer systems to assimilate nitrogen (N) from swine lagoon effluent. Replicated 30x4 m plots were established at the interface of a pasture and riparian forest. Wastewater from the third lagoon of th e University of Georgia Coastal Plain Experiment Station main swine re search unit was applied to each plot by overland flow from tanks at th e top end of each plot. The wastewater which contained an average N co ncentration of 160 mg L-1 N, primarily as ammonium (NH4-N), was applie d to the plots at two different rates (either once per week [1x, 1285 L/plot] or twice per week [2x, 2570 L/plot]). Three different vegetati ve buffer treatments were evaluated: (1) 10 m grass buffer draining in to 20 m existing riparian zone vegetation; (2) 20 m grass buffer drain ing into 10 m existing riparian zone vegetation; and (3) 10 m grass bu ffer draining into 20 m maidencane (Panicum hematomon). The effects of the wastewater on surface runoff and groundwater quality were evaluat ed 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 applicat ion rate and distance downslope from the wastewater application pipe. Nitrogen concentrations increased over time at the top ends of the plo ts bur showed little increase at the bottom ends of the plots. Overall , all three vegetative treatments were successful in assimilating N fr om the wastewater The study showed that riparian buffer systems, where wastewater is applied by overland flows can be effective in assimilat ing N contained within lagooned animal wastes.