MICROORGANISMS SURVEY IN THREE DIFFERENT ENVIRONMENTS OF CULTIVATED SOIL

Some species of microorganisms present in the soil can cause damage to agricultural and forestry crops due to their phytopathogenic potential. However, most of them have a function of maintaining the environment and biodiversity, like decomposition of organic matter indispensable in the biogeochemical cycles. These are also associated with environmental quality due to their sensitivity to variations in factors that compose the environment. The goal of this work was to quantify and identify, at the genus level, the fungi present in the soil of three different environments. The experiment was conducted at the Laboratory of Forest Pathology and Microbiology Soil of the Faculty of Agricultural Sciences at the São Paulo State University - UNESP in Botucatu, SP. Soils were collected from three different environments at 20 cm depth, from a seven years old eucalyptus forest area; a pasture area with more than ten years and an agricultural area with corn in a crop rotation management. Five grams of each treatment was added in saline solution and diluted until concentration of 105. Was added 1 ml of solution of each concentration in Petri dishes, followed by the addition of Martin medium culture with three replicates for each concentration and treatment. The Petri dishes were maintained in a B.O.D. chamber with photoperiod of 12 hours at 25°C±2 during seven days. After this period the number of fungal colony forming units (CFU) was quantified and the microorganisms was identified at the genus level. The CFU averages for each soil were compared by the Tukey test at 1% probability. Soil collected from the forest area showed a higher number of CFUs (4.47x104) followed by soils of pasture area (0.23x104) and soil of the agricultural area (0.03x104) that did not differ statistically to each other. The fungi present in the soils of the three environments were Aspergillus sp., Trichoderma sp., Penicillium sp. and Rhizopus sp., where the first three fungi represent 69% of the total quantified. We conclude with this work that the soil of the forest area of eucalyptus has the greatest microbiological activity, because this environment has high amount of organic matter and consequently more cycling of mineral nutrients, which favors the activity of microorganisms such as mycorrhizas.