NITRATE LEACHING DURING LONG-TERM SPRAY IRRIGATION FOR TREATMENT OF SECONDARY SEWAGE EFFLUENT ON WOODLAND SITES

Two waste water-treated sites at The Pennsylvania State University Wastewater Renovation Project were monitored to measure nitrate and total N in soil water. Both long-term waste water irrigation and varied irrigation rates were examined. Soil water was sampled by porous cup samplers. The concentration of N at the 120-cm depth was taken as a measure of N which escaped the root zone and which would leach to the ground water. Recharge volume was calculated from irrigation, rainfall, and potential evapotranspiration. A hardwood forest site located on a well-drained sandy loam soil was irrigated year round with secondary municipal effluent at a rate of 5 cm/week. An abandoned old field site planted with white spruce and located on a well-drained clay loam soil was irrigated with effluent at 5 cm/week from Apr. through Nov. each year, beginning in 1963. Results from both sites are reported.