Oxygen inhibition of denitrification in chloroform fumigated and non-fumigated soil

The effect of chloroform fumigation on O 2 inhibition of denitrification was evaluated in non-fumigated, fumigated and sterile soil with 0, 1, 2. 3 or 6% added O 2 using the C 2H 2 inhibition technique. Chloroform fumigation was used to lyse microbes and thereby release nitrate reductase which may decrease O 2 inhibition. With the fumigated treatment, soil samples were exposed to chloroform for 24 h followed by evacuation, whereas a CHCl 3 saturated atmosphere was maintained during the incubation in the sterile soil treatment. Nitrous oxide. CO 2 and O 2 in the headspace of incubation containers were measured over 10d. Denitrifiers apparently recolonized the fumigated soil within 12 h after chloroform removal. Oxygen inhibited denitrification in fumigated and non-fumigated soils. Oxygen consumption and CO 2 production were greater in fumigated than in non-fumigated soil samples as a result of the additional carbon from lysed microbes. Nitrite reductase appeared to be more sensitive to O 2 than nitrate reductase.