iwc: Integral Water Capacity

Description

Quantifying the soil water availability for plants through the IWC approach. The theory was based on the work of Asgarzadeh et al. (2014), using the van Genuchten-Mualem Model for estimation of the water retention curve and a simple power model for penetration resistance.

Usage

iwc(theta_R, theta_S, alpha, n, a, b, graph = TRUE,
	xlab = "Matric potential (hPa)", ylab = "Water content", ...)

Arguments

theta_R

the residual water content; a numeric parameter from van Genuchten's model; see details.

theta_S

the water content at saturation; a numeric parameter from van Genuchten's model; see details.

alpha

a scale parameter from van Genuchten's model; see details.

a shape parameter from van Genuchten's model; see details.

a parameter of the soil penetration resistance model; see details.

graph

logical; if TRUE (default), graphics for both dry and wet range are built.

xlab

a label for x-axis.

ylab

a label for y-axis.

...

further graphical parameters.

Value

A list of
IWCintegral water capacity
EIintegral energy calculation

Details

The parameters of the van Genuchten-Mualem Model can be estimated through the function fitsoilwater(). The soil penetration resistance model: $PR = a*h^b$.

References

Asgarzadeh, H.; Mosaddeghi, M.R.; Nikbakht, A.M. (2014) SAWCal: A user-friendly program for calculating soil available water quantities and physical quality indices. Computers and Electronics in Agriculture, 109:86--93. Groenevelt, P.H.; Grant, C.D.; Semetsa, S. (2001) A new procedure to determine soil water availability. Aust. J. Soil Res., 39:577--598.

Examples

Run this code

# example 1 (Fig 1b, Asgarzadeh et al., 2014)
iwc(theta_R = 0.0160, theta_S = 0.4828, alpha = 0.0471, n = 1.2982, 
	a = 0.2038, b = 0.2558, graph = TRUE) 

# example 2 (Table 1, Asgarzadeh et al., 2014)
iwc(theta_R = 0.166, theta_S = 0.569, alpha = 0.029, n = 1.308, 
	a = 0.203, b = 0.256, graph = TRUE) 

# End (Not run)

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