Hidrodinâmica em solos tipicos dos tabuleiros costeiros no Recôncavo da Bahia.

Abstract

The hydraulic conductivity of the soil is a property whose quantification is essential for any study that involves the movement of water in the soil. It is one of the most important hydraulic parameters for flow and transport related to phenomena in the soil. However, there is a concern about the appropriateness, efficiency and ease of application of the different methods of determination, given their high variability in space and time. In addition to varying with moisture, high spatial variability of hydraulic conductivity is detected in soil, both in field and laboratory determinations. In this work, the most common field and laboratory methods were tested in order to verify hydraulic conductivity in two types of soils: Yellow Latosol and Yellow Argisol in coastal tableland of the city of Cruz das Almas, Bahia. The experiment was divided in three parts, one for each method tested, and developed in the experimental field of the Federal University of the Recôncavo da Bahia, Cruz das Almas, Bahia State, Brazil. The "dry pit" method was carried out in the field, in a Yellow Latosol, at 10 points dispersed in the area under grazing use in degradation stage. In the same area, three samples were collected at depths 0-0.15; 0.15-0.30; 0.30-0.45 m in dispersed points in the area, totaling 360 samples, for the determination of the hydraulic conductivity in the laboratory by means of the constant charge permeameter. In the third part of the experiment, the instantaneous profile was installed in the experimental area of micrometeorology of the Nucleus of Water and Soil Engineering (NEAS), where the soil was described as Yellow Argisol. TenTDR probes were installed at each 0.1 m depth, in order to evaluate soil moisture and internal profile drainage for 131 days. The results of the field and laboratory methods demonstrated the high coefficient of variation for the hydraulic conductivity of the soil, and the first method obtained values of conductivity higher than the second. The instantaneous profile method showed adequate application to the coastal tableland soils, being able to detect the reduction of the moisture in the layers of density. All methods were able to discriminate the variation of soil hydraulic conductivity. The best choice of method application depends on the type required and the accuracy of the hydraulic conductivity measurement, soil type, cost and practical restrictions on its application.