NITRIFICATION POTENTIALS AT DIFFERENT PH VALUES IN PEAT SAMPLES FROM VARIOUS LAYERS OF A DRAINED MIRE

The dependence of nitrification in peat on pH was studied using aerobi c incubation of samples from a drained minerotrophic fen in central Fi nland. In aerobic suspensions of the surface layer (0-5 cm) the nitrif ication 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, stor age of the homogenized peat material at 4 degrees C changed the relati on of nitrification potential to pH. Inhibition of nitrification by ac etylene was stronger at the pH that gave the higher nitrification rate . Thus, acetylene inhibited nitrification almost totally at pH 6 in th e 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 su rface layer (0-17%). At pH 6 in the deeper layers, acetylene did not i nhibit nitrification at all.