The nitrification inhibitor DMPP had no effect on denitrifying enzyme activity

Denitrifying enzyme activity (DEA) and flux rates of nitrous oxide (N2O) and dinitrogen (N2) were studied in DEA assays on soils treated with 3,4-dimethylpyrazole phosphate (DMPP). Nitrous oxide and N2 fluxes were quantified by 15N gas-flux method with no additional enzymatic inhibitors, thus, overcoming problems associated with the use of chloramphenicol and acetylene. The nitrification inhibitor DMPP did not affect DEA or the measured gas emissions even when applied in concentrations 14 times higher than the recommended concentration.