Publication Summary

Nitrogen in soil pore-water was sampled at the Deer Park land application site in winter 1995-96 to follow up on a 1993 study. Composite winter samples were obtained from capillary wick (wick) soil pore-water samplers that accumulated water from October 1995 until April 1996. Ceramic cup suction pore-water samplers that were still intact were also sampled in April 1996.

Nitrogen in soil pore-water was sampled at the Deer Park land application site in winter 1995-96 to follow up on a 1993 study. Composite winter samples were obtained from capillary wick (wick) soil pore-water samplers that accumulated water from October 1995 until April 1996. Ceramic cup suction pore-water samplers that were still intact were also sampled in April 1996.

Although effluent is not applied to the fields between November and March, wintertime concentrations of nitrate+nitrite-N were similar to summer 1993 concentrations based on results from the wick samplers.

Twenty-three percent of an estimated total annual load of nitrate+nitrite-N percolating below the root zone occurred in the winter. The resulting increase in underlying ground water nitrate+nitrite-N concentration is estimated as 5 mg/L after one year. Because the crop overlying the samplers was not managed or harvested as were crops in the field, these estimates may not be as representative of conditions in the undisturbed field as estimates would be if the field and study area had been managed identically.

Monitoring networks that use wick soil pore-water samplers may be useful at other small municipal land application facilities in eastern Washington to provide an early warning of nitrogen impacts on ground water. Such networks would be especially useful at sites where complicated geology makes ground water monitoring difficult. Soil pore-water information could be useful for adjusting land application operations to prevent or minimize detrimental effects on ground water.

Link to EIM data for User Study ID BCAR0004