Variability of Soil CO2 Efflux in a Decatur Silt Loam Soil Under Different Tillage Systems.

Abstract The efflux of carbon dioxide (CO2) from soil surface presents an important component of organic carbon in terrestrial ecosystems, and it contains three times more carbon (2460 Pg C; Pg = 1015 gram) than present in the atmosphere (800Pg). As such, it plays a significant role in regulating atmospheric CO2 concentration. Soils have the potential to play a dual role as source and sink for carbon depending on the land use and soil management practices. The significant increase in intensive agriculture in the last century has contributed to the gross anthropogenic emissions of greenhouse gases. There is a concern that the present and future warming trend could trigger a massive CO2 release to the atmosphere through soil C respiration (soil CO2 efflux). Conservation or no-tillage management has been reported to increase soil organic matter (SOM) storage, probably because it hampers microbial mineralization of organic compounds. In order to better understand the variability of soil CO2 effluxes in different cultural systems, the soil CO2 efflux rates were quantified in till and no-till systems under corn – wheat rotation in a Decatur silt loam soils at Alabama A & M University Winfred Thomas Agricultural Research Station. Our ongoing objective is to evaluate the relationships between soil CO2 effluxes and soil bio-physical and chemical factors such as soil moisture, temperature, pH, organic matter content and microbial activity under till and no-tillage systems. Preliminary results showed that tillage practices had a notable influence on daily and monthly CO2 efflux during summer. The CO2 effluxes under mold board till were higher than under no-till. The increased CO2 effluxes detected in the tilled plots were probably due to increased disturbance, mixing and aeration of soil, which sped up decomposition of organic matter thus releasing more CO2 to the atmosphere. Key words: tillage system, soil CO2 efflux, infrared gas analyzer