Effect of substrate concentration, inorganic nitrogen, O2 concentration, temperature and pH on dehydrogenase activity in soil

Dehydrogenase activity was measured in a sandy loam soil under a variety of incubation conditions using the reduction of 2-(p-iodophenyl-3-(p-nitrophenyl)-5-phenyl tetrazolium chloride (INT) to iodonitrotetrazolium formazan (INT-formazan). There was a high positive correlation between dehydrogenase activity and substrate concentration, incubation temperature, and soil pH. Dehydrogenase activity also displayed a high negative correlation with O2 concentrations. Ammonium sulfate at concentrations from 40 to 120 μg/g soil had no significant effect on dehydrogenase activity. However, at concentrations of 160 and 200 μg/g, dehydrogenase activity was significantly reduced. Potassium nitrate at concentrations ranging from 40 to 200 μg/g had no significant effect on soil dehydrogenase activity, whereas sodium nitrite significantly inhibited activity at concentrations of 120 and 160 μg/g soil.