Abstract
The effects of some commercial herbicides and N-heterocyclic compounds structurally related to corn root constituents on N2O-emitting soil bacteria were examined. In the N2O emission assay, two N2O-emitting eubacteria, the incomplete denitrifier Pseudomonas sp. 10CFM5-1B and Pseudomonas sp. 10CFM5-2D (both isolated from Andisol corn farmland in Hokkaido), were used. We found that methyl viologen dichloride (Paraquat®) at 2 µM significantly repressed N2O emission by the active denitrifying bacteria. A corn antifungal secondary metabolite, 6-methoxy-2-benzoxazolone (MBOA), also repressed pseudomonad denitrifiers at a concentration of 10 µM. Other herbicides such as simazine (6-chloro-N,N′-diethyl-1,3,5-triazine-2,4-diamine) and amitrole (3-amino-1,2,4-triazole) accelerated N2O emission by Pseudomonas sp. 10CFM5-1B at 2 or 10 µM. It was thus shown that methyl viologen dichloride may have somewhat contributed to the repression of global warming by suppressing N2O production in farmland soils. Some herbicides, including amitrole and other triazole-type chemicals, may instead have the potential to activate soil N2O emission.
