[The effect of biocides on the microflora of soils and their degradation. 4. The influence of substances inhibiting the straw decomposition on the nitrogen transformation (author's transl)].

1. Active ingredients retarding the carbon-transformation of straw (TCP, Thiuram, TBTO) also retard the nitrification. Their active period depends on the concentration and on the presence of organic matter. High doses of urea can inhibit the nitrification as well. 2. The activity of urease and the ammonification could not be influenced by adequate doses of the tested active ingredients. 3. The species of bacterium Azotobacter fixing the nitrogen from the air were inhibited by TCP, urea and D-chloramphenicol and promoted by Thiuram and WTZ II 277 after a short period of inhibition. 4. The fungi are very important in the biological nitrogen fixation after manuring straw and in prevention of nitrogen leaching in the autumn. 5. The sufficient concentration of the active ingredients to inhibit the nitrification are lower than the fungicidal concentrations. The soil bacteria could even not be restrained by doses of 5000 ppm. The bacilli were more retarded in presence of organic matters than in a not manured soil.