Chemical Versus Microbial Decomposition of Amitrole in Soil

Abstract

Degradation of 3-amino-l,2,4-triazole-5-C14 (amitrole-5-C14) in autoclaved, potassium azide, ethylene oxide, and dry-heat sterilized soil was compared with that observed in nonsterile soils by measuring evolved C14O2. Amitrole degradation occurred in azide and ethylene oxide-sterilized and nonsterile soils but not in autoclaved soils. Only slight degradation occurred in autoclaved soil re-inoculated with mixed cultures of soil microorganisms isolated from soil in which amitrole had been rapidly degraded. Addition of EDTA-Na to nonsterile and ethylene oxide sterilized soils reduced amitrole degradation. Addition of organic amendments to amitrole treated soil stimulated microbial activity but reduced amitrole degradation. Addition of specific metallic salts to certain soils increased the rate of amitrole degradation. Amitrole degradation occurred rapidly in several free radical generating chemical systems. These results and additional observations indicate that amitrole degradation, at least in three soils examined, was largely a chemical process, and that microbial involvement was only indirect.