DETERMINAÇÃO DA CURVA DE RETENÇÃO PARCIAL UTILIZANDO TENSIOMETRIA

Abstract

Irrigation management based on soil relies on determining soil moisture through direct and indirect methods. The tensiometer is an indirect method that requires soil water retention curves to relate soil water tension to moisture content. These curves are commonly obtained in the laboratory using equipment such as the Richards pressure chamber, a precise but time-consuming and costly method. This study aimed to develop soil water retention curves for sandy and clayey soils using tensiometers to obtain partial retention curves. The experiment was conducted in a protected environment at the School Farm of the Federal Institute of Goiás – Posse Campus, using eight 11 dm³ pots, four filled with sandy soil and four with clayey soil. A porous-cup tensiometer was installed in each pot. After soil saturation and initial drainage, soil water tension was measured with a digital tensimeter, while the pots were periodically weighed to determine gravimetric soil moisture. The data were fitted to the van Genuchten model using SWRC software. The resulting curves showed coefficients of determination above 88% and low mean square error values, indicating a good model fit. In the sandy soil, tension ranged from 5 to 12 kPa, whereas in the clayey soil it ranged from 3 to 84 kPa, demonstrating a wider range of water retention. It was concluded that tensiometers provide a rapid and efficient method for developing soil water retention curves to estimate soil moisture near field capacity and support irrigation management. However, for irrigation system design, laboratory-generated retention curves are recommended because they cover a broader range of soil water tensions, including the permanent wilting point.