Name: VINÍCIUS ROCHA POLTRONIERI
Type: MSc dissertation
Publication date: 28/05/2020
Advisor:
Name |
Role |
|---|---|
| KÁTIA VANESSA BICALHO | Advisor * |
Examining board:
| Name |
Role |
|---|---|
| KÁTIA VANESSA BICALHO | Advisor * |
| MARISTELA GOMES DA SILVA | Internal Examiner * |
Summary: Knowledge of the soil water retention curve (SWRC) and the hydraulic conductivity curve (HCC) is
important in understanding the behavior of unsaturated soils. The called pedotransfer functions
(PTFs) are used to transform easy to measure data, such as the soil particle size distribution, into
data that are difficult to measure, such as SWRC and HCC. This dissertation investigates the
influence of the particle size distribution and textural classes on the SWRC and the HCC of a
hydrophysical database of Brazilian soils. The equation proposed by van Genuchten (1980) is
adopted to define the SWRC and HCC curves of these soils. The experimental data were
separated according to three classifications: (a) classification in 10 subgroups based on the
percentage of fines (Fc),
(b) classification in 5 textural classes based on the textural triangle called FAO (Food and
Agriculture Organization of the United Nations) and (c) classification in 12 textural classes based
on the USDA (United States Department of Agriculture) textural triangle. The analyzes were
compared with results obtained in the literature for temperate soils. The results suggest that the
influence of Fc is not observed in the adjustment parameters of the van Genuchten equation
(1980) for soils with Fc> 10% for HYBRAS soils and Fc> 30% for UNSODA soils. These parameters
should not be interpreted as having physical meaning. The influence of the soil particle size
distribution on saturated hydraulic conductivity and HCC is limited for the three investigated
classifications. In general, the information limited on the soil particle size distribution is not
enough to describe the variability of SWRC and HCC for the soils investigated in this research. It is
recommended caution in the use of PTFs for soils different from those used to define these
mathematical functions.
Keywords: Unsaturated soils, soil water retention curve, hydraulic conductivity curve, Brazilian
and temperate soils.
