Soil properties in organic olive groves compared with that in natural areas in a mountainous landscape in southern Spain

This study evaluates soil properties in organically managed olive groves and natural zones in a mountainous area of Andalusia, Spain. Two soil types (Eutric Regosol and Eutric Cambisol) and the most common soil management methods (tillage and two intensities of grazing) were studied. Both soil types in the groves had values not much lower than those in the natural areas. Average (+/- SE) values in the groves were 1.58 +/- 0.71% for organic carbon, 323 +/- 98 g kg(-1) for macroaggregate stability, 1.11 +/- 0.16 g cm(-3) for bulk density, 3.5 +/- 1.6 mm h(-1) for saturated hydraulic conductivity and 1209 +/- 716 mg CO2 kg(-1) for soil respiration. Overall, these values tended to be lower in the tilled compared with that in the grazed groves. The average phosphorus soil content (5.83 +/- 5.22 mg kg(-1)) was low for olive production and within adequate ranges for N (0.12 +/- 0.05%) and K (142 +/- 81 mg kg(-1)). Soil erosion was high in the tilled groves (35.5 +/- 18.2 t ha(-1) year(-1)) with soil loss correlating with indicators of soil degradation such as organic carbon content and water stable macroaggregates. In the grazed groves, soil loss was moderate with no clear indications of soil degradation. Overall, there was significant farm-to-farm variability within the same soil and land management systems. Olive production had a moderate effect on soil degradation compared with natural areas and olive cultivation could be sustained in future if cover crop soil management replaced tillage, especially in the most sloping areas.