Development of pedotransfer functions of hydraulic properties using ensemble models: a methodological proposal
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Data
2023-10-17Primeiro coorientador
Ottoni, Marta Vasconsellos
Primeiro membro da banca
Petry, Mirta Teresinha
Segundo membro da banca
Albuquerque, Jakson Adriano
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Soil water properties play a crucial role in various areas, including agriculture, engineering and
mathematical modeling. However, obtaining this data directly in the field or laboratory is timeconsuming and costly. An effective solution to speed up obtaining these properties is the use of
Pedotransfer Functions (PTFs), which take advantage of more accessible information, such as
soil physical and chemical properties, to predict more complex properties through regression
or machine learning methods. These PTFs can be divided into two main categories: Point-based
PTFs, which estimate water content at specific tensions, and Parameter-based PTFs, used to
predict mathematical parameters that describe water retention in the soil. Another way of
classifying PTFs is based on the types of physical data, resulting in Class PTFs and Continuous
PTFs. Class PTFs depend on a previous classification of the soil, often related to its texture, in
order to make predictions. On the other hand, Continuous PTFs establish empirical or semiphysical relationships with physical or chemical soil properties, using regression or similar
methods. In recent decades, hundreds of PTFs have been developed in Brazil. However, access
to these PTFs has been difficult due to their dispersion in inumerous publications. Furthermore,
the lack of a consolidated database containing validated PTFs and relevant information makes
selecting the appropriate PTF a complex task. The main objectives of this study were to conduct
a comprehensive survey of these PTFs calibrated for Brazilian soils, and validate their
performance against a database of national soils. Moreover, the study proposes the creation of
standardized metadata for the publication of new PTFs, suggests the adoption of enseble
models, and presents a computer software. The results of this survey revealed the existence of
336 equations, of which 292 are point-based PTFs and 44 are parameter-based PTFs, designed
to calculate the parameters of the van Genuchten (1980) equation. Most of these PTFs were
developed at a state level, showing better validation performance when applied to the regions
for which they were originally developed, compared to their application throughout the national
territory. The PTFs had clay as their main predictor, followed by silt and sand. The adoption of
ensemble models proposed through the computer software has the potential to make Brazil's
PTFs more accessible and effective in meeting user needs, by reducing prediction error and
improving the accuracy of soil property estimates. The use of these combined models makes
possible knowledge aggregation of various PTFs, taking advantage of their respective
advantages and mitigating their individual limitations. The computer program allows the
calculation of field capacity and permanent wilting point using the calibration site and the
lowest validation RMSE in the decision criterion.
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