Soil Science Department, Agricultural Collage, Ferdowsi University of Mashhad, Mashhad, Mashhad,
Sterilized soils are commonly used for the study of xenobiotic sorption and as an abiotic control in biodegradation experiments. They are also used for the chemical study of nitrogen and carbon cycle processes and the elimination of the biological factors. In this research the effects of different soil sterilization methods such as autoclaving, fumigating and exposure to ultraviolet and microwave irradiation on soil chemical and biological properties (soil acidity, electrical conductivity, cation exchange capacity, optical density, extractable carbon and nitrogen and colony forming unit) were examined under laboratory conditions. All the sterilization methods significantly (at P<0.05) decreased pH and increased electrical conductivity (EC), optical density (OD), extractable carbon and nitrogen as compared to non-sterilized soil samples. The results showed that autoclaving method was the most effective method in eliminating soil microorganisms and ultra violet irradiation was the less effective one. These induced changes were likely due to release of soluble organic acids from humic materials and dead microorganisms.