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.