Pesticides are commonly used for chemical treatment in the modern agriculture. Subtropical and tropical area with high temperature and rainfall cause serious problems in pest and deceases, which need to use more amounts of pesticides. For the proper utilization of pesticides, the objective of this project is to study the effect of pesticides on soil physical, chemical, and biological environments, to find the good method to disease the amount of application of pesticides.First year of this study focused on effect of pesticides on soil microorganisms. Second year was to focus that on soil environments. Third years were to write the application standard of pesticides. The project to study the effect of three pesticides, daconil (bactericide), paraguat (herbicide), and kestrel (insecticide), on fungi, actinomyceters and bacteria of Kuan-Yin and Hsin-Wu red soils. The results showed that fungal population in Kuon-Yin red soil decreased to 92% after 14th-day treated with daconil. Daconil was an effective bactericide. Paraquet and Kestrel affected less at the first period on fungi, actionomycetes and bacteria. The results indicated that bactericide (daconil) was more active than herbicide (paraquet) and insecticide (kestrel) on soil microorganisms. The results in Hsin-Wu red soil showed that daconil significantly stimulated actinomycetes population up to 3 times (192%). However, paraquat and kestrel had leas affect on soil fungi, actinomycetes, and bacteria. The results implicated that the concentration of pesticides is a main factor on the soil microorganisms. The effect of pesticides on benefit soil microorganisms, including decomposing activity, mixtures and regulation of pesticides, is discussed in the paper.
