Soil Structure and Porous System in Response to Plant Components of an Agrosilvopastoral System

Production systems of agroecological nature, such as agrosilvopastoral systems, have been considered as beneficial in various regions of the world. In semi-arid regions, these systems can contribute not only to food production, but also to soil conservation. Considering the specificities of each plant component, it is supposed that there is a different influence on soil structure, so that some components can be more efficient than others in the improvement of this structure. In the present study, the objective was to evaluate physical attributes with emphasis on the pore distribution, shape and size of a Luvisol in the influence area of different plant components of an agrosilvopastoral system in the semi-arid region of the Ceará state. The study was carried out in an agrosilvopastoral system established in the municipality of Sobral (Ceará, Brazil), with a completely randomized strip-plot design and four replicates. The treatments corresponded to three plant components: arbustive (Leucaena leucocephala), arboreal (Poincianella pyramidalis) and agricultural (Zea mays); and four soil layers: 0.0-0.05, 0.05-0.18, 0.18-0.25 and 0.025-0.41 m. For physical and micromorphometric analyses, undisturbed soil samples were collected in profiles in the areas covered by the plant components. The following attributes were analyzed: soil density, soil-air intrinsic permeability, soil-water characteristic curve, total porosity and pore distribution by shape and size. The soil under the influence of the components L. leucocephala and P. pyramidalis showed better structure, represented by the lower values of density, higher intrinsic permeability to the air and larger total area of pores, in comparison to the soil under the influence of Zea mays. The unfavorable result of the annual crop is due not only to the plant component, but also to the grazing of crop residues in the management system.