Nitrification potentials at different ph values in peat samples from various layers of a drained mire

Abstract

The dependence of nitrification in peat on pH was studied using aerobic incubation of samples from a drained minerotrophic fen in central Finland. In aerobic suspensions of the surface layer (0–5 cm) the nitrification rate was higher at pH 6 than at pH 4. Deeper in the profile (5–25 cm), nitrification was greater at pH 4 than at pH 6. However, storage of the homogenized peat material at 4°C changed the relation of nitrification potential to pH. Inhibition of nitrification by acetylene was stronger at the pH that gave the higher nitrification rate. Thus, acetylene inhibited nitrification almost totally at pH 6 in the surface layer (97%) and at pH 4 in the deeper layers (95–100%). Only weak inhibition by acetylene (2.5 kPa) was observed at pH 4 in the surface layer (0–17%). At pH 6 in the deeper layers, acetylene did not inhibit nitrification at all. Keywords: acetylene inhibitiondrainingmirenitrificationpeatland soil profilepH dependencysoil acidity