Abstract
Abstract. Soil organic carbon (SOC) concentration is a soil variable subject to changes. The management system is a key factor that influences these changes. To determine the long-term effects of the management system on SOC stocks (SOCS) in olive groves, 114 soil profiles were studied in the Los Pedroches Valley (Mediterranean rangelands – southern Spain) for 20 years. The management practices were conventional tillage (CT) and organic farming (OF) in four soil types: Cambisols (CMs), Regosols (RGs), Luvisols (LVs) and Leptosols (LPs). Soil properties were statistically analysed by management techniques, soil types and horizons. Significant differences (p < 0.05) were found between soil types and management practices. It was equally observed that the management system affected SOCS. In addition, the total SOCS during the 20-year experiment increased in OF with respect to CT by 72 and 66% in CMs and LVs respectively. SOC showed significant differences for horizons (p < 0.05) in relation to the management type. The stratification ratio (SR) was used as an indicator of soil quality based on the influence of surface SOC levels on erosion control, water infiltration and nutrient conservation with respect to deep layers. The SR of SOC from the surface to depth was greater in CT compared to OF with the exception of RGs. In all cases, the SR of SOC was >2. These results indicate high soil quality and that management practices affect SOC storage in the Los Pedroches Valley.
Highlights
Over the centuries, olive groves (OGs) have been a relevant social and economic heritage of Mediterranean areas
The soils in the Los Pedroches Valley are conditioned by lithology and the formation processes of these soils take place with low slope (Nerger et al, 2007), they are shallow soils (Marañón, 1988)
An important feature of these soils is the low OM content (González and Candás, 2004). This is justified by climatic conditions and soil texture, which contribute to a low organic matter content (Parras-Alcántara et al, 2013b, 2014b)
Summary
Olive groves (OGs) have been a relevant social and economic heritage of Mediterranean areas. The olive oil production in Andalusia (Spain) is more than 1.3 million tonnes, constituting 85 % of total Spanish production (MAGRAMA, 2012) and 41 % of what is produced worldwide (IOC, 2012). This activity has brought economic benefits to the region, but there have been adverse effects. Traditional OG management has been associated with soil erosion (Castro et al, 2008), river and water body pollution (Colombo et al, 2005), degradation of landscape (Parra-López et al, 2009), and climate change (Rodríguez-Entrena et al, 2012).
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