Leaching From Land Disposed Municipal Composts: 2. Nitrogen

Abstract

The leachates from 17 lysimeters containing compost of varying origin, age (3 and 12 months), and packing depths (15-50 cm) were monitored for a 2 1/2 year period. This paper reports on the results on nitrogen compounds. The leaching patterns for Kjeldahl-N and ammonia were comparable but significantly different from that of nitrate. The amount leached from the compost was affected by origin of compost (Kj.-N), age (Kj.-N, NH4, NO₃), and layer thickness (NO₃). The leaching of Kjeldahl-N was particularly high from 3-month compost in the thick layers. The total amount of nitrogen leached from the compost during the first 2 years accounted for 7-16% of the nitrogen content of the compost. The amount of ammonia and nitrate leached exceeded the initial compost contents of these components, indicating that further leaching of these compounds is governed by mineralization of organic nitrogen. The initial leachate concentrations exceeded drinking water standards several hundredfold indicating a significant risk of polluting the groundwater.