ptfkit.saxton2006¶
import ptfkit.saxton2006;
Exported namespace: ptfkit::saxton2006
Saxton and Rawls (2006), soil water characteristics from texture and organic matter.
Source¶
Saxton, K. E., & Rawls, W. J. (2006). Soil water characteristic estimates by texture and organic matter for hydrologic solutions. Soil Science Society of America Journal, 70(5), 1569-1578.
Scope¶
Territory: United States
Dataset: 1,722 mineral-soil A-horizon samples retained from the USDA/NRCS National Soil Characterization database after exclusions from 2,149 samples.
Saxton2006PTFResult¶
struct Saxton2006PTFResult {
double theta_1500;
double theta_33;
double theta_s;
double plant_available_water;
double air_entry_tension;
double retention_a;
double retention_b;
double conductivity_lambda;
double saturated_conductivity;
double normal_density;
};
| Field | Description |
|---|---|
theta_1500 | Volumetric water content at 1500 kPa matric tension. (m^3/m^3) |
theta_33 | Volumetric water content at 33 kPa matric tension. (m^3/m^3) |
theta_s | Saturated volumetric water content at normal density. (m^3/m^3) |
plant_available_water | Difference between the 33 and 1500 kPa water contents. (m^3/m^3) |
air_entry_tension | Air-entry or bubbling-pressure tension. (kPa) |
retention_a | Coefficient A of the dry-range moisture-tension curve. (kPa) |
retention_b | Exponent B of the dry-range moisture-tension curve. (dimensionless) |
conductivity_lambda | Inverse of retention exponent B. (dimensionless) |
saturated_conductivity | Saturated hydraulic conductivity of the matric soil. (mm/h) |
normal_density | Normal dry bulk density assuming particle density 2.65 g/cm^3. (g/cm^3) |
Saxton2006DensityResult¶
struct Saxton2006DensityResult {
double adjusted_density;
double adjusted_theta_s;
double adjusted_theta_33;
double adjusted_theta_s_minus_33;
};
| Field | Description |
|---|---|
adjusted_density | Density after applying the density factor. (g/cm^3) |
adjusted_theta_s | Saturated water content after the density adjustment. (m^3/m^3) |
adjusted_theta_33 | Water content at 33 kPa after the density adjustment. (m^3/m^3) |
adjusted_theta_s_minus_33 | Density-adjusted difference between saturation and 33 kPa. (m^3/m^3) |
Saxton2006GravelResult¶
struct Saxton2006GravelResult {
double gravel_volume_fraction;
double bulk_density;
double bulk_plant_available_water;
double bulk_saturated_conductivity;
};
| Field | Description |
|---|---|
gravel_volume_fraction | Gravel volume fraction of the bulk soil. (m^3/m^3) |
bulk_density | Dry bulk density of matric soil plus gravel. (g/cm^3) |
bulk_plant_available_water | Plant-available water on a bulk-soil volume basis. (m^3/m^3) |
bulk_saturated_conductivity | Saturated conductivity after the gravel reduction. (mm/h) |
Saxton2006SalinityResult¶
struct Saxton2006SalinityResult {
double saturated_osmotic_potential;
double osmotic_potential;
};
| Field | Description |
|---|---|
saturated_osmotic_potential | Osmotic potential at saturation. (kPa) |
osmotic_potential | Osmotic potential at the supplied water content. (kPa) |
Functions¶
calc_ptf_saxton2006¶
Estimate soil water characteristics from sand, clay, and organic matter.
[[nodiscard]]
inline Saxton2006PTFResult calc_ptf_saxton2006(double sand, double clay, double organic_matter)
Parameters¶
| Name | Description |
|---|---|
sand | Sand mass fraction of the fine-earth soil. (g/g) |
clay | Clay mass fraction of the fine-earth soil. (g/g) |
organic_matter | Organic matter content on a mass percentage basis. (% mass) |
Returns¶
A Saxton2006PTFResult value.
Note
Sand and clay are decimal mass fractions, while organic matter is a percentage.
Note
The 1500 and 33 kPa values are also termed wilting point and field capacity.
Warning
Do not apply the regression above 8% organic matter or 60% clay.
Warning
Sand and clay fractions must describe one soil and therefore must sum to at most 1.
Warning
These statistical-average estimates should be calibrated to local measurements when available.
calc_ptf_saxton2006_density¶
Adjust Saxton and Rawls water characteristics for soil density.
[[nodiscard]]
inline Saxton2006DensityResult calc_ptf_saxton2006_density(double normal_density, double theta_s, double theta_33, double density_factor)
Parameters¶
| Name | Description |
|---|---|
normal_density | Normal dry bulk density estimated by the base model. (g/cm^3) |
theta_s | Saturated water content at normal density. (m^3/m^3) |
theta_33 | Water content at 33 kPa and normal density. (m^3/m^3) |
density_factor | Multiplicative adjustment to normal density. (dimensionless) |
Returns¶
A Saxton2006DensityResult value.
Note
The source limits the saturation-minus-33 kPa difference to at least 0.005 m^3/m^3.
Warning
The source recommends density factors only from 0.9 to 1.3.
calc_ptf_saxton2006_tension_dry¶
Estimate matric tension in the 1500 to 33 kPa segment.
[[nodiscard]]
inline double calc_ptf_saxton2006_tension_dry(double theta, double theta_1500, double theta_33)
Parameters¶
| Name | Description |
|---|---|
theta | Volumetric water content. (m^3/m^3) |
theta_1500 | Volumetric water content at 1500 kPa. (m^3/m^3) |
theta_33 | Volumetric water content at 33 kPa. (m^3/m^3) |
Returns¶
Matric tension at the supplied water content. (kPa)
Warning
Use only for the 1500 to 33 kPa segment defined by the source.
calc_ptf_saxton2006_tension_wet¶
Estimate matric tension in the 33 kPa to air-entry segment.
[[nodiscard]]
inline double calc_ptf_saxton2006_tension_wet(double theta, double theta_33, double theta_s, double air_entry_tension)
Parameters¶
| Name | Description |
|---|---|
theta | Volumetric water content. (m^3/m^3) |
theta_33 | Volumetric water content at 33 kPa. (m^3/m^3) |
theta_s | Saturated volumetric water content. (m^3/m^3) |
air_entry_tension | Air-entry tension estimated by the base model. (kPa) |
Returns¶
Matric tension at the supplied water content. (kPa)
Note
At tensions below air entry, Equation 13 fixes water content at theta_s.
Warning
Use only for the 33 kPa to air-entry segment defined by the source.
calc_ptf_saxton2006_conductivity¶
Estimate unsaturated hydraulic conductivity from water content.
[[nodiscard]]
inline double calc_ptf_saxton2006_conductivity(double theta, double theta_s, double saturated_conductivity, double conductivity_lambda)
Parameters¶
| Name | Description |
|---|---|
theta | Volumetric water content. (m^3/m^3) |
theta_s | Saturated volumetric water content. (m^3/m^3) |
saturated_conductivity | Saturated hydraulic conductivity of the matric soil. (mm/h) |
conductivity_lambda | Inverse of retention exponent B. (dimensionless) |
Returns¶
Unsaturated hydraulic conductivity at the supplied water content. (mm/h)
Warning
The equation does not include residual water content.
calc_ptf_saxton2006_gravel¶
Adjust matric-soil properties for gravel content.
[[nodiscard]]
inline Saxton2006GravelResult calc_ptf_saxton2006_gravel(double gravel_weight_fraction, double matric_density, double plant_available_water, double saturated_conductivity)
Parameters¶
| Name | Description |
|---|---|
gravel_weight_fraction | Gravel mass fraction of the bulk soil. (g/g) |
matric_density | Dry bulk density of the fine-earth matric soil. (g/cm^3) |
plant_available_water | Plant-available water of the matric soil. (m^3/m^3) |
saturated_conductivity | Saturated hydraulic conductivity of the matric soil. (mm/h) |
Returns¶
A Saxton2006GravelResult value.
Note
Gravel comprises particles larger than 2 mm.
Note
Gravel density is fixed at 2.65 g/cm^3 in the source equations.
Warning
The conductivity correction does not represent extra macropores sometimes found in gravelly soils.
calc_ptf_saxton2006_salinity¶
Estimate saturated and moisture-adjusted osmotic potential.
[[nodiscard]]
inline Saxton2006SalinityResult calc_ptf_saxton2006_salinity(double electrical_conductivity, double theta, double theta_s)
Parameters¶
| Name | Description |
|---|---|
electrical_conductivity | Electrical conductivity of a saturated soil extract. (dS/m) |
theta | Current volumetric water content. (m^3/m^3) |
theta_s | Saturated volumetric water content. (m^3/m^3) |
Returns¶
A Saxton2006SalinityResult value.
Note
The moisture adjustment assumes dissolved salt quantity remains near constant as water content falls.
Warning
Precipitation, bonding, ionic nutrition, and toxicity can modify actual salinity effects.