Nitrogen transformations in an aerobic soil as determined by a ¹⁵NH₄⁺ dilution technique

The rates of mineralization, immobilization and oxidation of N in an aerobic soil, an Andosol Brown, from the farm of the Hokkaido National Agricultural Experiment Station were simultaneously determined in the presence and absence of acetylene using a ¹⁵NH⁺₄ dilution technique. C₂H₂ inhibited nitrification, but did not directly affect mineralization and immobilization. Denitrification and immobilization of NO₃^--N were negligible. Mineralization proceeded much faster than did immobilization. Net mineralization accounted for 22-59% of gross mineralization. The rates of N transformation at a water content of 60% were higher than those at 40%. The Q₁₀ values for mineralization, immobilization and nitrification were estimated, between 11° and 29°C, to be 2.0, 1.9 and 1.7, respectively.