Polynomial functions to predict flux-based field capacity from soil hydraulic parameters

Author(s)

Inforsato, Leonardo ^[1] ; van Lier, Quirijn de Jong ^[1]

Affiliation

^[1] Univ Sao Paulo, Ctr Nucl Energy Agr CENA USP, POB 96, BR-13416903 Piracicaba, SP - Brazil

• Document type: Journal article
• Source: Geoderma; v. 404, DEC 15 2021.
• Web of Science Citations: 0

Abstract

We propose two new polynomials as pedotransfer function, PTF, to predict the flux-based Field Capacity water content, Theta(FC). The inputs for the PTF are the bottom flux criterium, the profile depth, and the retention and conductivity parameters of the Van Genuchten - Mualem model, VGM. A first polynomial was developed including all VGM parameters and a second polynomial considers VGM parameter l equal to 0.5, the most commonly applied value. The polynomials were built using stepwise multiple linear regression and a generated dataset over a wide range of VGM model parameters. The ``observed values{''} for the polynomial calibration were acquired from internal drainage simulations performed by the Richards equation-based model SWAP. The derived polynomials predicted the simulated Theta(FC) with high accuracy. The RMSD between observed and predicted Theta(FC) on tested datasets, for the complete version and the l = 0.5 polynomial version were, respectively, 0.01912 and 0.01362. The proposed polynomials may be combined with other PTFs providing the VGM parameters from texture and/or other basic data. Examples of predicted FC water content and pF are shown on texture triangles using the Rosetta PTF to predict VGM parameters from soil texture data. For stand-alone use, the polynomials allow predicting the flux-based Theta(FC) from VGM parameters without the need for numerical simulations. (AU)

• FAPESP's process: 20/00145-2 - Development of methodology to obtain soil hydraulic properties assisted by evaporation experiment in laboratory
• Grantee: Leonardo Inforsato
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 18/20902-2 - Development and functional evaluation of laboratory methods to determine soil hydraulic properties and their relation to crop water availability
• Grantee: Quirijn de Jong van Lier
• Support Opportunities: Regular Research Grants