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United States Department of Agriculture

Agricultural Research Service

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CalcPTF - Abstract

Multimodeling with Pedotransfer Functions: PTF Calculator

Simulations of soil water flow are often carried out with parameters estimated using pedotransfer functions (PTFs), which are empirical relationships between the soil hydraulic properties and more easily obtainable basic soil properties available, for example, from soil surveys. The use of pedotransfer functions is necessary when the simulations have to be done for large-scale projects, or for pilot studies. Results of PTF applications are always uncertain, because the accuracy of pedotransfer functions outside of its development dataset is unknown. The use of several PTFs (multimodel ensemble prediction techniques) has been shown to be an efficient approach for estimating hydraulic properties within an uncertainty context. The computer program PTF calculator (CalcPTF) has been developed to estimate parameters of the Brooks and Corey and van Genuchten water retention equation to support the multimodeling approach. Seven PTFs estimate the Brooks and Corey parameters, four PTFs estimate the van Genuchten parameters, and five models fit the van Genuchten equation to pairs (capillary pressure, water content) estimated with PTFs. The PTF calculator also estimates the net capillary drive parameter of the three-parameter Parlange infiltration equation. The code is written in FORTRAN and can be invoked from an Excel worksheet or run as a stand-alone. Examples of input and output files are given.

Soil column (left) and its pore space (right)rendered with computer tomography.

Images by Andrey Guber and Fernando Jose Martinez.
Soil column (left) and its pore space (right) rendered with computer tomography.

Environmental Microbial and Food Safety Laboratory
Henry A. Wallace Beltsville Agricultural Research Center, Beltsville, MD 20705
Building 173 BARC-East, Phone 301.504.5607

Last Modified: 8/12/2016
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