Influence of soil management on soil physical characteristics and water storage in a mature rainfed olive orchard

Mechanical tillage represents the most common technique of soil management in olive orchards within the Mediterranean Basin. Such practice may result in soil structure degradation which can significantly reduce water infiltration causing runoff and erosion processes. An alternative opportunity is given by the use of cover crops which eliminates most of the disadvantages of conventional tillage. An experiment was carried out from 2007 to 2009 in a mature and rainfed olive grove located in Southern Italy with the aim to evaluate the effect of different soil management techniques on soil structure and soil water content and storage along the profile. The experimental site was characterised by a slope gradient ranging from 0 to 16%. Since 2000, the olive grove was subjected to two different management systems: sustainable system, SS (no-tillage, spontaneous vegetation cover, annual recycling of pruning material) and conventional system, CS (tillage, no recycling of pruning material). Modifications of soil structure induced by the two different management systems were quantified by micromorphometric analysis macroporosity. Soil hydrological behavior was determined by field saturated hydraulic conductivity (K-sat) measurements. Soil water content was measured at 10/15-day intervals by gypsum resistivity blocks placed in flat and steep areas (summit, backslope, and footslope) of both systems at different soil depths (25, 50, 75, 100, 150 and 200 cm). In the SS soil macroporosity was not very high (about 10%) but homogeneously distributed along the profile which favored the vertical water movement down to deeper horizons. In the CS the occurrence soil crusting and of compacted layers along the profile hindered infiltration and percolation of rainfall water influencing the soil water content below the 100 cm layer. The SS was able to better store water from rainfall, received during the autumn-winter period, especially in the deepest soil layer (from 100 to 200 cm). This was evident especially in the steep area at the summit position, where the water amounts stored by SS were 45 and 17% higher than those retained by the CS in 2007 and 2009, respectively. During summer such reserves were available for the olive root systems which usually, under the driest conditions, explore the deep soil zone in search of water. Under our experimental conditions, no yield reduction was observed due to the prompt mowing of the spontaneous cover crops. Therefore, the suitable use of cover crops should be communicated to the olive farmers and strongly recommended within agricultural policy strategies for its evident agronomical and environmental benefits (increase of soil organic carbon, soil structure improvement, reduction of soil and water losses, carbon sequestration). (C) 2014 Elsevier B.V. All rights reserved.