Perdas de solo e de nutrientes por erosão hídrica em Luvissolos sob processo de desertificação no estado de Pernambuco

Abstract

Desertification is a problem of continental dimensions that occurs in regions with arid, semi-arid and dry sub-humid climates and is characterized by the degradation of natural resources. Approximately 57% of Northeast Brazil has a semi-arid climate and is experiencing intense changes in land use that have resulted in severe soil degradation due to water erosion. One of the main strategies adopted to study this problem at the local level was the establishment of desertification centers. Six nuclei are recognized in Brazil: Gilbués (PI), Irauçuba (CE), Seridó (PB), Cariris Velhos (PB), Sertão do São Francisco (BA) and Cabrobó (PE). Despite the existence of many works developed in this region, the vast majority have as their main research focus vegetation and anthropic influence on land degradation. Studies characterizing the rates of loss of soil, water and nutrients, as well as investigating the influence of soil physical properties on the acceleration of erosion are still scarce, especially in the Desertification Center of Cabrobó. Therefore, the main objective of this study was to quantify and characterize soil and water losses, as well as the depletion of total macro (CaO, MgO, K2O, P2O5) and micronutrients (MnO, Fe2O3) due to the water erosion of Luvisolos located in the Pernambuco semiarid region. In addition, it was intended with this research to verify the influence of physical and chemical properties of the soil on the speed of soil degradation by erosion. For that, experimental erosion plots of 1m wide by 3m long were installed. The results will be presented in two chapters. In the first chapter, the monitoring of soil losses was carried out under two precipitation conditions (60 and 100 mm h-1) using a rain simulator. To evaluate the effect of vegetation, the experiment was conducted in Luvisolos with different vegetation coverings. In the second chapter, to verify the relationship between soil properties and the erosion process, samples were collected around the experimental plots subjected to the rain simulations of the two Luvisols studied. The collected samples were analyzed physically and chemically, and the observation of the relationship between these properties and the intensity of the erosion process was carried out through the application of principal component analysis (PCA). From the results it was possible to observe that both the intensity of the rains and the vegetation cover significantly influenced the losses of water, soil and nutrients. It was also possible to observe that in Luvisolo with greater vegetation coverage, both physical and chemical properties were found. more preserved and this was reflected in the low generation of runoff and consequently erosion. In conclusion, the data obtained from this study indicate that the community's relationship with the environment in the Cabrobó Nucleus must be reconsidered, practices such as deforestation, burning and intensive grazing by small ruminants must be abolished in order to minimize degradation by action erosion.