Response of microorganisms and enzymes to soil contamination with a mixture of pethoxamid terbuthylazine

Abstract

This study analysed the effect of a mixture of pethoxamid (P) and terbuthylazine (T) contained in the herbicide Successor T 550 SE on organotrophic bacteria, total oligotrophic bacteria, Azotobacter and actinomycetes, oligotrophic sporulating bacteria, fungi and on the activities of dehydrogenases, catalase, urease, alkaline phosphatase, acid phosphatase, arylsulphatase and β-glucosidase. The phytotoxic effect of this pesticide on maize was also determined. The study was undertaken because of a lack of data concerning the effect of a P+T mixture on soil metabolism. The previously undertaken studies concerned only the separate effect of each of these substances. The P+T mixture disturbed soil homeostasis and altered soil stability, resulting in a succession of K-strategy organotrophic bacteria. It had a negative effect on bacteria of the genus Azotobacter, oligotrophic sporulating bacteria, actinomycetes and fungi, and a positive effect on oligotrophic bacteria. P+T in doses greater than 0.73 mg kg−1 of soil resulted in a strong inhibition of dehydrogenases, catalase, urease, acid phosphatase, alkaline phosphatase, arylsulphatase and β-glucosidase, and significantly inhibited the growth and development of maize.