Organic farming has little effect on carbon stock in a Mediterranean dehesa (southern Spain)

Understanding soil dynamics is essential for making appropriate land management decisions, as soils can affect the carbon content from the atmosphere, emitting large quantities of CO2 or storing carbon. This property is essential for climate change mitigation strategies as agriculture and forestry soil management can affect the carbon cycle. The Mediterranean dehesa (Mediterranean grassland ecosystem with scattered oak trees — grazing system with Quercus ilex spp. ballota) is a silvopastoral system that integrates forestry, agricultural and livestock practices. The dehesa is characterized by the preservation of forest oaks that provide environmental services including carbon capture and storage. This paper shows the relationships between soil properties and soil organic carbon (SOC) in two soil types: Cambisols (CM) and Leptosols (LP), with two management systems: organic farming (OF) for 20 years and conventional tillage (CT) in a Mediterranean dehesa of southern Spain without cropping. An analysis of 85 soil profiles was performed in 2009 in Los Pedroches Valley (Cordoba, southern Spain). The SOC stock (SOC-S) was greater in CM (75.64 Mg ha− 1) than in LP (44.01 Mg ha− 1). Physical parameters were the main variables affecting soil development. SOC-S was very similar in OF and CT (CM [74.90 Mg ha− 1-CT; 76.39 Mg ha− 1-OF] and LP [44.77 Mg ha− 1-CT; 43.25 Mg ha− 1-OF]). Data analysis showed that management practices had little effect on SOC storage in the study zone. Significant differences between soil types and management practices were found in SOC content for different horizons. The stratification ratio was > 2 in both soils types (CM and LP) and management systems (OF and CT). These results indicate that the soil is of high quality, and that management practices have little influence on SOC-S in Los Pedroches Valley.