soilphysics: soilwater5 – R documentation

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soilwater5

Soil Water Retention, based on the modified van Genuchten's formula

Description

Function to calculate the soil water content based on the modified van Genuchten's formula, as suggested by Pierson and Mulla (1989):

θ = θ_R + (θ_S - θ_R)(1 + (α x)^n)^{-m} + b_0 + b_1 x + b_2 * x^2

Usage

soilwater5(x, theta_R, theta_S, alpha, n, m = 1 - 1/n, b0, b1, b2)

Arguments

`x`	the matric potential.
`theta_R`	the residual water content.
`theta_S`	the water content at saturation.
`alpha`	a scale parameter of the van Genuchten's formula.
`n`	a shape parameter in van Genuchten's formula.
`m`	a shape parameter in van Genuchten's Formula. Default is 1-1/n (Mualem, 1976).
`b0`	a parameter added to the van Ganuchten's formula.
`b1`	a parameter added to the van Ganuchten's formula.
`b2`	a parameter (of quadratic term) added to the van Ganuchten's formula.

Value

The the soil water content or the saturation index (a value between 0 and 1).

Author(s)

Anderson Rodrigo da Silva <anderson.agro@hotmail.com>

References

Pierson, F.B.; Mulla, D.J. (1989) An Improved Method for Measuring Aggregate Stability of a Weakly Aggregated Loessial Soil. Soil Sci. Soc. Am. J., 53:1825–1831.

Examples

soilwater5(x = 20, theta_R = 0.2735, theta_S = 0.478, alpha = 0.1029, 
	n = 9.45, b0 = 0.2278, b1 = -0.0165, b2 = 0.000248)
curve(soilwater5(x, theta_R = 0.2735, theta_S = 0.478, alpha = 0.1029, 
	n = 9.45, b0 = 0.2278, b1 = -0.0165, b2 = 0.000248), 
	from = 0, to = 40,
	ylab = "Water content",
	xlab = "Matric potential")

# End (Not run)

soilphysics

Soil Physical Analysis

v4.0

GPL (>= 2)

Authors

Anderson Rodrigo da Silva [aut, cre] (<https://orcid.org/0000-0003-2518-542X>), Renato Paiva de Lima [aut] (<https://orcid.org/0000-0003-0524-439X>)

Initial release

2020-12-06