# soilwater3: Soil Water Retention, based on the Dexter's (2008) formula In soilphysics: Soil Physical Analysis

## Description

Function to calculate the soil water content based on the Dexter's (2008) formula. It is based on the segregation of pore space in two categories what are called bi-modal pore size distributions. In this model, the pore space is divided into two parts: the textural porosity which occurs between the primary mineral particles, and the structural porosity which occurs between micro aggregates and/or any other compound particles. This is called the double-exponential (DE) water retention equation, given by:

θ = θ_R + a_1 \exp(-x/p_1) + a_2 \exp(-x/p_2)

where θ is the gravimetric water content.

## Usage

 `1` ```soilwater3(x, theta_R, a1, p1, a2, p2) ```

## Arguments

 `x` a numeric vector containing the values of applied air pressure. `theta_R` a parameter that represents the residual water content. `a1` a parameter that represents the drainable part of the textural pore space in units of gravimetric water content at saturation. `p1` a parameter that represents the applied air pressures characteristic for displacement of water from the textural pore space. `a2` a parameter that represents the total structural pore space in units of gravimetric water content at saturation. `p2` a parameter that represents the applied air pressure that is characteristic for displacing water from the structural pores.

## Value

The the soil water content.

## Author(s)

Anderson Rodrigo da Silva <[email protected]>

## References

Dexter et al. (2008). A user-friendly water retention function that takes account of the textural and structural pore spaces in soil. Geoderma, 143:243-253.

`fitsoilwater3`, `soilwater`, `soilwater2`

## Examples

 ```1 2 3 4 5``` ```soilwater3(x = 0, theta_R = 0.058, a1 = 0.233, p1 = 3.274, a2 = 0.070, p2 = 1.78) soilwater3(x = 3, theta_R = 0.058, a1 = 0.233, p1 = 3.274, a2 = 0.070, p2 = 1.78) soilwater3(x = 4, theta_R = 0.058, a1 = 0.233, p1 = 3.274, a2 = 0.070, p2 = 1.78) # End (not run) ```

soilphysics documentation built on May 30, 2017, 2:49 a.m.