Effects of acetylene on nitrification and denitrification in two soils during incubation with ammonium nitrate

A loam from the Frilsham and one from the Wickham Series were incubated at 50 and 90 per cent of their water contents at saturation with 100 μg NH₄NO₃-N_g^?1 soil in the presence and absence of C₂H₂ (0.5 per cent, v/v). Acetylene inhibited nitrification in both soils, but had no effect on mineralization of N. No denitrification (measured as the production of N₂O in the presence of C₂H₂) occurred during incubation at 50 per cent saturation. At 90 per cent saturation, denitrification resulted in a loss of 28.4 and 36.7 μg N_g^?1 after 48 h from the Frilsham and Wickham soils, respectively. The concurrent inhibition of nitrification had no effect on the extent of denitrification at this time. In the Wickham soil, NO₃^? was exhausted after 168 h incubation in the presence of C₂H₂ and denitrification was underestimated by 13 μg N_g^?. The data suggested that concurrent inhibition of nitrification during measurement of denitrification using the C₂H₂ inhibition technique is most likely to affect the estimate of denitrification loss when NO₃^?supply is limited by the inhibition of nitrification.