Avaliação de equações de pedotransferência (PTF) para estimativa de parâmetros físico-hídricos dos solos das bacias hidrográficas dos rios Ivinhema, Amambai e Iguatemi - Mato Grosso do Sul

Abstract

The acquisition of soil physical-hydrical parameters is often challenging and costly. Pedotransfer functions (PTFs) allow the estimation of soil physical-hydrical parameters from more easily obtained data. This study aimed to evaluate the reliability of PTFs in estimating soil bulk density (Ds), soil volumetric moisture at field capacity - 10 kPa (θCC), and at the permanent wilting point - 1500 kPa ( PMP) for the predominant soils in the Ivinhema, Amambai, and Iguatemi river basins in Mato Grosso do Sul. The PTFs were selected in a hierarchical system: i) calculating median values of θCC and PMP solely based on textural grouping, ii) calculating median values of θCC and PMP based on the soil class associated with textural grouping, and iii) calculating values of Ds, θCC and PMP Ds using selected PTFs with the predictors: particle size distribution and soil organic carbon content. To evaluate the best accuracy of PTF predictions, the lowest RMSE values, the highest R² values, and graphical analysis were considered. The results indicated that when only the textural grouping is known, it is recommended to use θCC values of 0.110 cm³ cm⁻³ and PMP values of 0.043 cm³ cm⁻³ for the sandy group, 0.250 cm³ cm⁻³ and 0.143 cm³ cm⁻³ for the medium group; 0.365 cm³ cm⁻³ and 0.278 cm³ cm⁻³ for the clayey group, and 0.381 cm³ cm⁻³ and 0.296 cm³ cm⁻³ for the very clayey group. For the soil classes that occur most extensively in the studied area, the Latossolos Vermelhos (Ferralsols) in the medium, clayey, and very clayey textural groups, the recommended θCC values are 0.214, 0.395, and 0.356 cm³ cm⁻³, and the PMP values are 0.118, 0.282, and 0.276 cm³ cm⁻³, respectively. For the second most common soil class, the Neossolos Quartzarênicos (Arenosols), the θCC value is 0.110 cm³ cm⁻³ and the PMP value is 0.037 cm³ cm⁻³. For parameter estimation by predictors, the most accurate PTFs are those proposed by Huf dos Reis et al. (2024) for Ds, by Reichert et al. (2020) for θCC, and by Oliveira et al. (2002) for θPMP.