Atributos físicos do solo como indicadores do grau de degradação em áreas remanescentes da Caatinga em Triunfo - PE

Abstract

The saturated hydraulic conductivity of the soil (Ksat) is considered a physical property of the soil that quantifies the water movement through the soil pores, through the space and infiltration time. Thus, Ksat is one of the most important properties related to the soil water dynamics and has been cited as one of the indicators of the soil structural quality. In cases of water erosion and environmental degradation, this property supports in decision making to define soil management and type of cultivation, aiming to preserve soil and environment. The determination methods of Ksat can be applied in situ, allowing the maintenance of the environmental conditions; but also, in the laboratory, where the tests conditions are controlled. The biome called Caatinga is exclusive to Brazil and is found in large part of the semiarid region, with atypical characteristics comparing to other regions; thus, notice the importance of studying and understanding this biome. In this sense, the objective of this research was to diagnose the degradation degree of remaining areas of the caatinga in Triunfo - PE, using saturated hydraulic conductivity, evaluating the effect of the use of these areas on the soils water dynamics under herbaceous cultivation and cactus forage. Soil samples undisturbed were collected at the 0.0 – 0.10 and 0.10 - 0.20 m depths by the Uhland sampler with volumetric cores (volume  100 cm3) to Ksat tests. Disturbed samples, collected at the same depths, were used for particle size analysis, degree of flocculation and dispersion, silt/clay ratio, particle density and soil water content. The Ksat values obtained in the areas with Caatinga, herbaceous and cactus forage were, respectively, 9.66, 7.04, and 6.21 cm h-1, indicating the Caatinga and cactus forage as areas of reduced and greater degradation, respectively, and the area under herbaceous with medium level of degradation. The interactions of Ksat values with some soil physical attributes suggest that the different behaviour of soil water dynamics under herbaceous and cactus forage cultivation can also be evaluated by these attributes. Thus, the highly significant and positive correlations between Ksat and sand fraction and the flocculation degree of the clay fraction were highlighted; as well as the highly significant and negative correlations with the total clay, clay dispersed in water, and dispersion degree, ratifying the increasing order of degradation: Caatinga < herbaceous < cactus forage..