Funções hidráulico-energéticas na análise da qualidade física de Neossolos sob diferentes usos em escala de bacia hidrográfica

Abstract

Understanding the dynamics of water in the soil and the influence of different uses is one of the main pillars of water resource management in river basins. Several soil attributes have been used to describe the physical quality of the soils. However, they disregard processes related to the behavior of water retention in the soil. Alternatively, the indexes based on the energies related to the soil water retention curves (SWRC) appear, being applicable in any study location, regardless of the scale and the characteristics of the place. In this sense, this study aimed to evaluate the physical quality of Entisol under different uses from the use of hydraulic energy functions in an experimental grid containing 170 soil samples, established in the Sanga Ellert sub-basin, located in the municipality of Canguçu - RS. Bulk density, total porosity, macroporosity, microporosity, and SWRC were determined in the laboratory. Subsequently, the five hydraulic energy indexes (Aa, Wra, Ar, WRr and AWr), and the CRAS parameters (θs, θr, alpha, n, m). The data sets were subjected to descriptive and multivariate statistical analysis to understand the relationships between soil attributes, hydraulic energy indexes, and different soil uses. The different uses statistically influenced the indices of hydraulic energy, being evident that the energies of aeration and water retention in the soil of the hydrographic basin of the Sanga Ellert are directly related to the uses. The Native Forest has a good physical quality of the soil, soils under annual crops are the use that requires more energy for the plant to remove water from the soil and less energy to reach θfc, being the use where there is the most significant imbalance between these energies. Due mainly to its lower macroporosity, the soil under Pasture required greater work on the gravitational potential to drain the water from saturation to field capacity.