Soil solarization is an environment-friendly soil pasteurization technique which uses the solar energy to increase the soil temperature to diminish soil-related pests and pathogens. The efficiency of this technique is closely related with a number of factors such as soil water and organic matter contents and feature of cover material; therefore, the effect of solarization was studied under applications of CO2, basaltic tuff (BT), organic matter (OM) and a different color plastic cover (PE2) on soil temperature and microbial activity as dehydrogenase enzyme activity (DHA) and soil respiration (CO2). The trial was carried out in a greenhouse for 32 days. Organic matter, salt and lime contents, pH and texture class of greenhouse soil were 1.7%, 0.055%, 38.5%, 7.7 and clay, respectively. According to the results, while the lowest CO2 value was determined as 12.9 mg/100 g ds. 24 h in the A6 (PE2) application, the highest CO2 value was determined as 16.3 mg/100 g ds. 24 h in the A4 (+OM 1.5 kg/m2) application. The dehydrogenase enzyme activities (DHA) yielded similar results with the applications, however, the highest value (291.2 µg TPF/10 g ds.) was in A7 (control). Soil (0-5 cm) temperatures varied between 28.1 and 60.1°C with applications and the lowest soil temperature was determined in the control plot. The effect of the applications to soil temperature led to significant differences statistically (p<0.05). The results documented that the organic matter (OM) and CO2 amendments (OM or +OM+CO2) had a role in protecting soil microbial activity (dehydrogenase-DHA) and soil respiration (CO2) from the detrimental effects of the heating of solarization
