Alterações morfológicas de horizontes superficiais sob processo de desertificação após pousio

Abstract

The fallow practice is an important resource in the recovery of degraded and desertified soils, but the studies of pedogenetic actions in these soils are scarce. Thus, the objective of this study was to analyze changes in the surface horizons of soils submitted to fallow in a region under desertification process. Based on the hypothesis that the time of 13 years of fallow was enough to cause changes in the physical attributes (water infiltration), morphological and micromorphological attributes of the soil surface horizons. The experiment was carried out in a nucleus of desertification in the municipality of Irauçuba, semi-arid region of Brazil. For the present study, the morphological description of the surface horizons of the soils in the field was first carried out, then undisturbed samples were collected for micromorphological analysis of the surface horizon of a fallow area, excluded from domestic animals for 13 years, and in an area used with Extensive overgrazing livestock. Infiltration tests with 4 replicates per area were also performed. Then, thin slides of the undisturbed samples were made and descriptions of the micromorphological characteristics were made. The infiltration test was submitted to Student's t test at 5% probability. In the micromorphological analysis, a higher value of coarse material was observed in the soil in an overpass, in relation to the soil under fallow, evidencing the pedogenetic processes of elutriation and lowering, it was also verified that the soil under fallow presented porosity of 35%, being greater than in the area in excess of 20%. The infiltration test did not present a significant difference for the averages of the analyzed areas, but values represented in graphs show that in the initial instants the infiltration of water in the fallow soil was superior to the one of the overpass, denoting greater porosity in the superficial layer of the soil under fallow, corroborating what was observed in the micromorphological analysis. The morphological description also confirms what was observed in the micromorphological analysis, with greater emphasis on the darkening of the surface horizon in the fallow due to the melanization process due to the addition of organic matter, responsible for the greater porosity in this soil. As conclusion, it was observed that the soil submitted to 13 years of fallow presented morphological and micromorphological changes in relation to the overgrazed soil, presenting no difference in water infiltration.