Inhibition of nitrification in soil by heterocyclic nitrogen compounds

Summary The relationship between the structures of diverse heterocyclic nitrogen (N) compounds and the effectiveness of these compounds for the inhibition of nitrification in soil was studied by determining the effects of different amounts of 12 unsubstituted and 33 substituted heterocyclic N compounds on the production of (NO ₂ ^– +NO ₃ ^– )-N in soils incubated at 25 °C for 21 days after treatment with ammonium sulfate. The results showed that unsubstituted heterocyclic N compounds containing two adjacent ring N atoms inhibit nitrification in soil and that two of these compounds, pyrazole and 1,2,4-triazole, are potent inhibitors. They also showed that several substituted pyrazoles and thiadiazoles are good inhibitors of nitrification in soil (e.g., 3-methylpyrazole and 3,4-dichloro-1,2,5-thiadiazole).