[The effect of biocides on the microflora of soils and their degradation. I. The selection of suitable biocides and ways of selective influences in soil-microorganisms (author's transl)].

The influence of 544 biocides on soil-microflora was investigated by a special plate-test and by a soil-test. Fungi were particularly sensitive to active substances. They were more inhibited by a greater number of substances, by lower concentrations and by a larger time-interval than bacteria. A differentiated sensitivity of fungi becomes apparent. The pseudomonads, a species of Agrobacter (AIA), flavobacteria and some coryneforme bacteria were relatively resistant. Actinomyces responded similar to fungi. The plate-test is suitable as preliminary test for the selection of substances retarding the degradation of straw. These organisms already favoured by treatments with active substance locate in higher quantities in such soils where the biological balance was disturbed in after the injection. Therefore, the effect of the active substance exceeds that of the injection. The displacement-effect by bacteria resistant to active substances and little active against cellulose plays a minor role in opposite to bacteria active against cellulose, because bacteria don't develop any homogeneous protective coat. A priority effect is therefore excluded.