Development and application of a resin-bag method to determine available nitrogen in forest soils

A resin-bag method was compared to a conventional KC1 extraction procedure for determining available nitrogen in forest soil. Under controlled growth room conditions, both the amounts of ammonium and nitrate nitrogen adsorbed by resin-bags and extracted by 6% KC1 correlated well with the uptake of nitrogen by birch seedlings from 6 widely differing soils. Also, resin-bags placed in situ under 5 differing forest stands and one upland grassland plot gave a close relationship between their adsorption of nitrogen and a KC1 extractable nitrogen from the soil. This provides further evidence that the resin-bag method can be used to assay nitrogen availability in forest soils.