Conversion of 15N-ammonium in forest soils

To determine the fate of atmospheric ammonium in forest soils, one calcareous and two acid forest soils were incubated with ¹⁵N ammonium. In the calcareous soil about 65% of the applied ¹⁵N-ammonium was recovered as nitrate after 98 days of incubation, whereas in the acid soils less than 10% of the ¹⁵N-ammonium was converted to nitrate. In all soils a large proportion of the ¹⁵N was incorporated in organic nitrogen compounds. This incorporation limits the use of ¹⁵N tracers for the elucidation of the fate of atmospheric ammonium in soils.