Nitrate Leaching During Long-term Spray Irrigation for Treatment of Secondary Sewage Effluent on Woodland Sites1
- J. E. Hook and
- L. T. Kardos2
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. In the last 6 of 9 years of effluent treatment 83% of the 4,954 kg N/ha added leached from the site. Nitrate concentration in soil water at the 120-cm depth was generally > 15 mg N/liter. The hardwood forest was also ineffective in keeping nitrate concentration below 10 mg N/liter at the 120-cm depth when the 5-cm weekly application was split into two 2.5-cm irrigations or when it was lowered to 2.5 cm/week year round.
An abandoned old field site planted with white spruce (Picea glauca Moench) 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. Nitrate concentration at the 120-cm depth rarely exceeded 10 mg N/liter and only 36% of the 1,246 kg N/ha applied leached during the 6th through the 9th years of this effluent treatment. In the 10th and 11th years, when the application rate was increased to 7.5 cm/week, nitrate concentration exceeded 10 mg N/liter at the 120-cm depth, and the amount of N which leached increased to 75% of the amount applied.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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