PREDICTING UREA HYDROLYSIS AT LOW TEMPERATURES IN BRITISH COLUMBIA FOREST SOILS

Abstract

Urease activity in 14 sites, representing a wide range of forest and soil types, was determined by a non-buffer method. Urease activity in L-H horizons ranged from 23–203 μg N hydrolyzed (g soil)−1 h−1 at 40 °C. In all soils, urease activity decreased dramatically with depth. At 0 °C, hydrolysis was estimated at 26.8 and 1.9 μg N g−1 h−1 for L-H and Bf horizons, respectively, for one site. Theoretical estimation of hydrolysis at 0 °C for the site with the lowest activity suggested that an operational application of urea (200 kg N ha−1) applied to snow could be hydrolyzed within 6 days in the rooting zone of all the soils studied. Key words: Urease activity, energy of activation, forest fertilization, Brunisols, Luvisols, Podzols