Avaliação de atributos físicos como indicadores de qualidade solo e estimativa de propriedades hidrodinâmicas em diferentes pedoambientes e profundidades no Semiárido Brasileiro.

Abstract

Soil is a non-renewable natural resource, exhibiting high vulnerability that compromises its physical, chemical, and biological quality. This fragility is even more evident in arid and semi-arid regions, where shallow, sandy, or stony soils predominate, with low water retention capacity and high susceptibility to erosion. In the Caatinga biome, the replacement of native vegetation with extensive pasture systems or conventional agriculture intensifies structural degradation manifested by processes such as soil compaction from animal trampling or machine traffic, the formation of surface crusts, resulting in reduced porosity, increased apparent density, and decreased saturated hydraulic conductivity—factors that limit water infiltration, water availability, and root development of plants. In contrast, Agroforestry Systems (AFS) emerge as a sustainable alternative, promoting a greater input of organic matter, improving soil attributes, and achieving hydrological balance. This thesis aims to analyze and comparatively estimate how the pedoenvironments of the Brazilian Semi-Arid region (preserved caatinga, caatinga replaced by pasture, and caatinga replaced by agroforestry systems) influence the physical quality and hydrodynamic properties of the soil at different depths. To this end, the hypothesis was established that: the replacement of native Caatinga with different land uses alters the physical quality and hydrodynamic properties of the soil at different depths in the Semi-Arid region. Furthermore, the changes are more intense in the surface layers, while the deeper layers are less influenced by land use. In order to answer this hypothesis, two scientific articles were developed and published in the Brazilian Journal of Environmental Management and Sustainability: the first, entitled "Analysis of physical attributes as indicators of soil quality under different land use and depth conditions in the Brazilian Semi-Arid region," and the second, "Use of the Beerkan methodology to estimate hydraulic conductivity and soil sorbency in different land uses and depths in the Brazilian Semi-Arid region." The thesis is organized into four chapters: Chapter I presents an introduction, Chapters II and III correspond to the two published articles. Chapter IV presents the conclusions. The research used disturbed and undisturbed soil samples, in addition to conducting water infiltration tests and soil penetration resistance tests in three areas and at three depths. In the first article, physical attributes were evaluated: soil density; particle density; soil porosity; soil moisture; soil texture; and soil mechanical resistance to penetration. To assess the physical quality of the soil, two indicators with their respective optimal ranges or critical limits were used: Soil Density (Ds) and Soil Penetration Resistance (RP). The results were processed using Excel software to obtain descriptive statistics and the RStudio program for a Bootstrap analysis. Then, the t-test was applied to identify confidence intervals and generate the graphs. The Caatinga biome presented the functioning of the studied physical attributes as a natural reference for conservation. The agroforestry system proved to be a promising strategy for improving and maintaining the physical quality of the soil in the semi-arid region, while the pasture showed conditions of soil compaction, highlighting the need for conservation management practices to mitigate degradation processes and promote soil sustainability. In the second article, water infiltration tests were performed in the soil using a simple ring infiltrometer to estimate, through the Beerkan method, the physical-hydric attributes: saturated soil moisture; soil hydraulic conductivity; and soil sorbency. To evaluate the physical quality of the soil, hydraulic conductivity was used as an indicator chosen from the literature with its respective optimal or critical limit ranges. The results were processed using Excel software to obtain descriptive statistics and the RStudio program for a Bootstrap analysis. Subsequently, the t-test was applied to identify confidence intervals and generate graphs. The preserved Caatinga presented the best values, ensuring greater infiltration and structural quality of the soil. Pastureland shows the lowest results due to compaction and reduced macroporosity; and agroforestry systems occupy an intermediate position, contributing to the partial recovery of hydrological functions. The results obtained in this research will contribute to deepening the knowledge about the effects of land use at different depths in the Semi-arid region.