Side effects of some pesticides on non‐target soil microorganisms

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Abstract
Different methods were tested for their suitability to assess the effects of chemicals on soil microbial activity: determination of ATP‐content, respiration and fluorescein diacetate (FDA) hydrolysis. Fresh soil was either used immediately or amended with 0.5 % alfalfa meal, in order to improve the conditions of the microorganisms. The chemicals were applied in concentrations of 2, 20 and 200/μg.g‐1 . As herbicides, atrazine, pentachlorophenol, 4‐chloroaniline and chloroacetamide were used, as fungicides zineb (zinc ethylene‐1,2‐bis‐dithiocarbamidate) and captan (n‐trichloromethylthiote‐trahydrophthalimide), as insecticides lindane (γ‐hexachlorocyclohexane) and 4‐nitrophenol, and as a bactéricide, HgCl2. The observations were limited to 48 days. The effects caused by atrazine, lindane and cap‐tan were minor. The remaining pesticides induced measurable changes in the behaviour of microorganisms: while higher concentrations caused mostly reversible or irreversible reductions in ATP‐content and in FDA‐hydrolysis, small concentrations sometimes produced stimulative effects. The production of CO was stimulated by several pesticides in various concentrations. Improvement of soil by the addition of alfalfa meal promoted the reversibility of effects caused by chemicals.