Pedotransfer functions for the estimation of soil water retention in Brazilian soils.

  • Tomasella J
  • Hodnett M
  • Rossato L
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Abstract

Various studies have shown that micro-aggregated, strongly weathered
tropical soils have different water retention properties than temperate-region
soils because of differences in mineralogy and weathering history.
Hence, pedotransfer functions (PTFs), derived from data from temperate-region
soils (temperate PTFs) have limitations when applied to tropical
soils. In the absence of PTFs specifically for tropical soils, temperate
PTFs are being applied worldwide in global climate modeling exercises,
regardless of their textural validity. We derived a PTF to predict
the water retention parameters of the van Genuchten (1980) equation
using data from more than 500 Brazilian soil horizons. A modified
approach was adopted: Multiple regression was used to derive coefficients
that relate the van Genuchten parameters to basic soil data, followed
by re-optimization of those coefficients by fitting the individual
water content estimations to the measured data simultaneously. Pedotransfer
functions were developed for four levels of availability of basic
soils data and validated using independent data from 113 Brazilian
soil horizons. Water retention curves were better predicted by the
new PTFs than by two temperate PTFs tested: The root mean square
deviation (RMSD) ranged from 3.78 to 5.84, compared with 9.08 and
10.44, respectively. The new PTFs performed better even when the
comparison was restricted to the range of textural validity of the
temperate PTFs. For the proposed PTF, RMSDs increased with increasing
silt content, but decreased for the temperate PTFs, This reflects
the differences in silt content between temperate and strongly weathered
tropical soils.

Author-supplied keywords

  • BULK-DENSITY
  • HYDRAULI
  • PARTICLE-SIZE DISTRIBUTION

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Authors

  • J. Tomasella

  • M.G. Hodnett

  • L. Rossato

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