FATE OF INORGANIC N-15 IN THE PROFILE OF DIFFERENT CONIFEROUS FOREST SOILS

The fate of inorganic N-15 added to different coniferous forest soils was traced throughout the soil profile (0 - 25 cm) in a laboratory experiment under controlled conditions of temperature and water content. Six soils with different chemical climates were compared. The sequestration of labelled N was significantly explained by the clay content but the correlation was improved when C and N content were included. The level of acidification, even in soil with a fine texture, reduced the immobilization. For a similar N input, sandy soils with low C content or high acidification showed a reduced N storage capacity, so that N excess would be able to pollute the groundwater.