The recognition of using solar energy for soil solarization in protected agriculture is gaining ground as the ecological awareness of the public has increased. The primary main effect of solarization is to increase soil temperature. The determination of soil thermal properties before solarization can provide a key criterion for making a decision in regard to the benefit of solarization at a particular site. A two-year study was carried out in glass and plastic greenhouses under mainly clay and sandy soil conditions in the East-Mediterranean Region of Turkey, respectively. Three different applications of solarization were tested: solarization, solarization Plus CO2 application, and solarization plus manure application. Solarization was applied on individual plots of 2 m x 2 m using transparent polyethylene mulching from 6 to 8 weeks in July and August. CO2 and manure were applied as additions to the solarization for increasing the effectiveness of solarization. Soil temperatures were recorded continuously at 15 min. intervals, measured at 5, 20 and 30 cm depths. The soil thermal diffusivity was calculated using temperature data of the soils in a temperature-amplitude equation derived from re-arranging the heat equation. It was observed that soil thermal diffusivity increased in proportion to the increase of water content. The result showed that thermal diffusivity was higher under clay soil conditions in the glasshouse compared to sandy soil conditions in the plastic greenhouse. The highest values for the soil temperatures were observed at 20 cm and 35 cm soil depths at the volumetric soil water contents of 0.285-0.290 cm(3) cm(-3) and 0.315-0.330 cm cm, respectively. Measured temperatures varied between 55 and 57 degrees C at 5 cm depth, while maximum soil temperatures were obtained under CO2 application at 5 cm depth. It was concluded that an effective soil solarization can be achieved when soils were tilled, wetted with CO2 or covered with manure.