Evaluation of sewage sludge as a soil amendment in relation to nitrate leaching.

摘要

Nitrate leaching may be a major problem in certain soils after intensive use of nitrogen fertilizers. Moderate use of organic amendments, i.e. sewage sludge can supply available N and reduce the accelerating use of conventional fertilizers, which may lead to slower nitrate leaching. The aim of this study was to examine nitrate mobility in Mediterranean soils of low organic matter content using soil leaching columns amended with sewage sludge and inorganic fertilizer. Eight soil samples from the Gulf of Kalloni Lesvos Island, which typically bear the above mentioned characteristics, were used. It was found that sludge application at 10 t ha-1 increased nitrate retention capacity of soils either by rendering a smaller amount of nitrates available to leaching or by reducing the rate of NO₃-N release. Average NO₃-N leaching was 0.016 in control, 0.092 in sludge treatment, and 0.130 in fertilizer treatment (units in mg N kg-1 soil mm-1 eluted water). After about 100 mm of added water, cumulative leaching of NO₃-N reached a plateau in most soils, but nitrate recovery was a fraction of the added, probably due to denitrification- and immobilization-related N losses.