In soil science, analytical procedures apply almost exclusively to the fine earth (<2 mm). Rock fragments or skeleton (>2 mm) are regarded as inert and discarded during sieving; however, we have found that the clasts display physical and chemical properties that can equal or surpass those of the fine earth. These properties depend largely on the degree of alteration of the clasts. In light of these findings, we developed a method to separate the rock fragments into weathering classes. This method has been applied to five European skeleton‐rich soils derived from different parent materials. Color intensity, roughness and irregularities of the surfaces, cracks, and surface features of the exposed minerals were considered reliable criteria for the separation of the clasts. We noticed also that the degree of alteration of the clasts corresponds to size: as size decreased, weathering increased. Consequently, sieving could be used for separating the weathering classes. On the basis of these criteria, clasts were differentiated into highly, moderately, and slightly altered. There are statistically significant differences among the weathering classes in terms of bulk density, porosity, organic C, total N, and cation‐exchange capacity. There are no statistically significant differences in pH. The results confirm that the procedure separates relatively homogeneous and different classes of rock fragments. We also compared the characteristics of the soil skeleton to those of the fine earth and fresh rock. We concluded that not characterizing the skeleton of the soils may provide distorted information on the capability of these substrata.
The long-term effects of two different soil management practices, natural grass cover (NC) and conservation tillage (CT), on soil functions (carbon sequestration, habitat for organisms, and water movement and retention) were determined in a high-density, mature olive orchard (Olea europaea L. cv.Frantoio) growing in a sandy loam soil (Typic Haploxeralf) in a Mediterranean environment. Ten years after the beginning of the different soil management, soil samples were collected at 0-10 and 10-20 cm depth and at two distances from the trunk, underneath the olive canopy (UC) and in the inter-row (IR).There were no differences in fruit yield, oil yield, and yield efficiency between the two soil management systems during the 2011-2013 period. CT negatively affected soil organic carbon pools (total and humified), but only at the IR position. The distance from the plant did not significantly influence soil structure and hydrological properties, while NC treatment increased water movement and retention.Tillage reduced the microarthropod diversity, namely Collembola and 'Other arthropods', which were the most sensitive groups to soil perturbation. We conclude that natural grass cover was more effective than conservation tillage in maintaining or improving elements of soil functionality.
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