Abstract
The estimation of non available soil variables through the knowledge of other related measured variables can be achieved through pedotransfer functions (PTF) mainly saving time and reducing cost. Great differences among soils, however, can yield non desirable results when applying this method. This study discusses the application of developed PTFs by several authors using a variety of soils of different characteristics, to evaluate soil water contents of two Brazilian lowland soils. Comparisons are made between PTF evaluated data and field measured data, using statistical and geostatistical tools, like mean error, root mean square error, semivariogram, cross-validation, and regression coefficient. The eight tested PTFs to evaluate gravimetric soil water contents (Ug) at the tensions of 33 kPa and 1,500 kPa presented a tendency to overestimate Ug 33 kPa and underestimate Ug1,500 kPa. The PTFs were ranked according to their performance and also with respect to their potential in describing the structure of the spatial variability of the set of measured values. Although none of the PTFs have changed the distribution pattern of the data, all resulted in mean and variance statistically different from those observed for all measured values. The PTFs that presented the best predictive values of Ug33 kPa and Ug1,500 kPa were not the same that had the best performance to reproduce the structure of spatial variability of these variables.
Highlights
The understanding of the dynamics of the water in the soil-plant-atmosphere system, including the water availability to crops, infiltration, drainage, water stress and solute movement, depends on the knowledge of the relation between the soil water content and the matric potential, represented by the soil water retention curve (SWRC)
Different from those observed for all measured values
The cross-validation technique was employed to verify the quality of the fit to the spherical model of the experimental semivariogram, with the results evaluated through the coefficient of determination (R2) of the regression between estimated and measured values, and through those measured by the regression coefficient (RC), which is a measure of the
Summary
The understanding of the dynamics of the water in the soil-plant-atmosphere system, including the water availability to crops, infiltration, drainage, water stress and solute movement, depends on the knowledge of the relation between the soil water content and the matric potential, represented by the soil water retention curve (SWRC). Few studies present PTFs developed for tropical or subtropical soils and, especially, not for lowland soils. The contributions of Pidgeon (1972), Lal (1979), Aina & Periaswamy (1985), Dijkerman (1988) and van den Berg et al (1997) are of special interest. It is important to know more about the applicability of PTFs developed for these soils, to other soils that do not belong to the data pool used to generate them. These PTFs are suitable to describe the structure of the spatial variability of the soil attributes generated by them
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