EFFECT OF PESTICIDES USED FOR SEED TREATMENT OF POTATOES ON MICROBIAL ACTIVITIES IN SOIL

Under laboratory conditions the effect of practical doses of the fungicides ''Monceren'' (pencycuron) and ''Risolex'' (tolclofos-methyl), normally used for seed treatments of potatoes, on microbial activities in two soils were investigated. In parallel trials soil moisture and organic amendment were varied. The nitrification as well as microbial activities related to microbial biomass (dehydrogenase = TTC-reduction; glucose-induced short-term respiration) were only slightly affected by the pesticides. Carbon mineralization (long-term respiration), however, was inhibited in a sandy soil and stimulated or inhibited in a loamy soil. The nitrogen mineralization was less clearly influenced. Soil moisture and lucerne meal caused some modifications of these results. The relationship between mineralized carbon and nitrogen was strongly changed by lucerne meal, but only little by the pesticides.