Mayr and Jarvis (1999) modified Brooks-Corey water-retention parameter PTFs.¶
Source¶
Mayr, T., & Jarvis, N. J. (1999). Pedotransfer functions to estimate soil water retention parameters for a modified Brooks-Corey type model. Geoderma, 91(1-2), 1-9.
DOI: 10.1016/S0016-7061(98)00129-3
Scope¶
Territory: England and Wales
Dataset: Soil Survey and Land Research Centre soil physical properties database; regressions used 286 soil horizons retained from a 306-horizon subset after excluding fits with RMSE greater than 0.05 m^3/m^3, and validation used 1678 independent soil horizons.
Functions¶
calc_ptf_mayr1999¶
Estimate modified Brooks-Corey a, b, and saturated water content from texture, bulk density, and organic carbon.
Status: implemented
Prediction target: Hutson-Cass modified Brooks-Corey water-retention parameters a, b, and saturated volumetric water content.
Models: \(h(\theta)\) — Hutson-Cass modified Brooks-Corey water-retention model
Inputs¶
| Name | Type | Unit | Domain | Description |
|---|---|---|---|---|
sand | number | % | 0 <= value <= 100 | Sand content for particles 0.063-2.0 mm. |
silt | number | % | 0 <= value <= 100 | Silt content for particles 0.002-0.063 mm. |
clay | number | % | 0 <= value <= 100 | Clay content for particles 0-0.002 mm. |
bulk_density | number | g/cm^3 | value >= 0.9 | Dry bulk density; the paper excludes application below 0.9 g/cm^3. |
organic_carbon | number | % | 0 <= value <= 5 | Organic carbon content; the paper excludes application above 5%. |
Outputs¶
| Name | Unit | Domain | Description |
|---|---|---|---|
a_hc | cm H2O | value > 0 | Hutson-Cass fitting parameter with pressure-head dimensions. |
b_hc | dimensionless | value > 0 | Hutson-Cass fitting parameter controlling retention-curve shape. |
theta_s | m^3/m^3 | 0 <= value <= 1 | Volumetric soil water content at saturation. |
Note
The particle-size inputs use the UK size boundaries stated by the paper; sand, silt, and clay are percentages.
Note
The source reports r^2 values of 0.34 for log(a), 0.74 for log(1/b), and 0.84 for theta_s.
Note
Human review resolved the source's unspecified log base as base 10; the implementation therefore interprets log(a) and log(1/b) as log10 values.
Warning
Do not apply the functions to organic soils with organic carbon above 5% or soils with dry bulk density below 0.9 g/cm^3.
Warning
Treat application outside the calibration particle-size distribution with great care; the paper provides that distribution only graphically.