Conservation tillage systems (CTs) are expanding in different regions of Iran. On the other hand, study on tillage systems effects on chemical and biological properties of soil, which likely affect CO2 flux rates to the atmosphere and organic C content (OC) is important. The objective of this study was to compare soil respiration (SR) rates and OC among different tillage systems. For this purpose, a four replicated experiment was carried out in Randomize Completely Block Design with seven treatments in a wheat field in Hashemabad Reaserch Center of Gorgan in 2010. The treatments were different cultivation methods including CT by Kombinate, No-tillage by Baldan grain drill, CT by Chizelpacker, CT by Delta model, surface tillage by heavy disk, non-incorporated by Chizel and disk and conventional tillage by moldboard plow and twice disk. SR and OC were measured during spring season in 0-15 cm depth in 3 stages. SR rates at the beginning of the season in different CTs ranged from 0.17-0.26 mg CO 2.gr -1 soil.day-1 . These values at the end of the season ranged from 0.02-0.05. Results showed SR rate was different in different stages. During time, SR rate reduced with decreasing moisture and increasing temperature. There was no difference among cultivation treatments in respect to SR rate. OC values were different among cultivation treatments. The most OC was related to no-tillage followed by CT Kombinate. The lowest OC was related to conventional tillage. Our results indicated that to maintain soil OC and improve soil biological activities, CT is an alternative option to prevent or alleviate soil degradation.

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