各種農薬の土壌徴生物に及ぼす影響

Effects of 20 species of herbicides and 8 species of insecticides (technical products) on microorganisms were tested under laboratory conditions. Soil microorganisms were isolated by plate dilution methods using selective media containing the chemicals in various concentrations. NIP, PCP and disulfoton had influence on colony formation of soil fungi and bacteria on the plate agar containing these chemicals up to 10 ppm. The colony formation of soil fungi was affected by 10 chemicals among the 28 at 100 ppm, and that of soil bacteria was affected by 16 chemicals. Changes in soil microorganisms as influenced by MCP and other 6 species were investigated by colony counts of total fungi and bacteria from soil treated with the chemicals (formulation on the market). Samples were taken at intervals from the test tubes in which the chemicals-treated soil were incubated. Bacterial populations in the chemicals-treated soil showed a wide variety of the changes, however, the populations of fungi in the soil decreased under that in non treated soil. There was no clear correlation between the antibiosis of the chemicals tested on the media and the effects of those on microbial populations in the soil except PCP and DCPA. Species of fungi isolated from the chemicals-treated soil decreased in number during the incubation period.