Conservation Tillage Influence on Carbon Dynamics Under Mediterranean Conditions

Intensity of tillage practices can enhance organic matter decomposition, increasing CO2 emissions from soil to the atmosphere. Conservation tillage (CT) has been proposed as a means of counteracting potential damages to the environment. In this study the effects of two CT systems, reduced tillage in a long-term experiment (RTL) and no-tillage in a short-term experiment (NTS), were compared to traditional tillage (TT) in the long (TTL) and short-term experiments (TTS). CO2 fluxes, total soil organic carbon (SOC) and dehydrogenase activity (DHA) were evaluated at 0-5, 5-10 and 10-15 cm depths throughout the three years studied (Oct. 2006-Jul. 2009). Traditional tillage increased CO2 emissions compared to CT. The CT treatments (RTL and NTS) accumulated more SOC in the surface layer (0-5 cm) than the TT treatments (TTL and TTS). SOC accumulation was moderate but DHA consistently increased in CT in the surface soil, especially with a legume crop included in the crop rotation. Values of stratification ratio of all parameters studied were higher in the CT treatments (RTL and NTS). The agricultural and environmental benefits derived from CT make this system recommendable for semi-arid Mediterranean rain-fed agriculture.