Study of some quality parameters for different types of soil in SE Spain, in relation to their management as a basis for land planning

摘要

The area of study is located in the centre of the Murcia region, in Southeast Spain, under a semiarid Mediterranean climate. These soils are subject to an eminently agricultural use (60 %). The main uses correspond to marginal degraded areas, unirrigated tree cultures, irrigated cultures (trees and horticultural varieties), orchard cultures, soil prepared for cultivation and uncultivated soil with unaltered vegetation. As field parameters the following have been considered: type of soil, use, depth, water erosion, drainage and structure. Chemical parameters referring to organic carbon and total nitrogen contents, carbonitrogen ratio and soil salinity have also been determined. Systematic sampling of every km~2 was carried out, taking 30 cm deep samples from the soil surface. A total of 42 samples were obtained. The field parameters indicate that this is an area where a greatly effective soil depth predominates. The most significant symptoms of physical degradation are surface sealing and sheet, rill and gully water erosion, especially in Calcaric Regosols set for unirrigated and irrigated tree cultures. These soils usually show lack of structure and heavy drainage. As for analytic data, the predominance of low or very low contents of organic carbon and total nitrogen is stressed, particularly in Regosols. These contents increase slightly in soils set for irrigation cultures, giving rise to low C/N ratios. Although most soils are not (or just slightly) affected by salinity, the most significant values are also observed in irrigated cultures, where the original material may contribute these salts. The results obtained reveal, as shown on the cartographic study, that inadequate management negatively influences soil quality; because of which soil evaluation prior to land management is rendered essential.