psd {soilphysics}

Soil Pore Size Distribution

Description

The unimodal soil pore size distribution based on van Genuchten's model.

Usage

psd(thetaS, thetaR, alpha, n, h)

Arguments

thetaS

the water content at saturation.

thetaR

the residual water content.

alpha

the scale parameter of the van Genuchten's model (hPa-1).

n

the shape parameter in van Genuchten's formula.

h

a vector of water tension (hPa) on the range of water retention curve.

Value

A numeric vector containing the soil pore size distribution as a function of soil water tension.

Author(s)

Renato Paiva de Lima <[e-mail]>

References

Ghiberto, P. J., Imhoff, S., Libardi, P. L., Silva, A. P. D., Tormena, C. A., Pilatti, M. A. (2015). Soil physical quality of Mollisols quantified by a global index. Scientia Agricola, 72(2):167-174.

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.

Examples

# EXAMPLE 1
x <- seq(log10(1),log10(15000),len=100)
h <- 10^x
y <- psd(thetaR = 0.15,thetaS = 0.55, alpha = 0.048, n = 1.5, h=h)
plot(x=h,y=y, log="x", xlab="h (hPa)", ylab=expression(delta*theta/delta*h), ylim=c(0,0.005))

# EXAMPLE 2
x <- seq(log10(1),log10(15000),len=100)
h <- 10^x
y <- psd(thetaR = 0.20,thetaS = 0.61, alpha = 0.1232, n = 1.3380,h=h)
plot(x=h,y=y, log="x", xlab="h (hPa)", ylab=expression(delta*theta/delta*h), ylim=c(0,0.01))

# EXAMPLE 3
x <- seq(log10(1),log10(15000),len=100)
h <- 10^x
y <- psd(thetaR = 0.154,thetaS = 0.600, alpha = 0.103, n = 2.365,h=h)
plot(x=h,y=y, log="x", xlab="h (hPa)", ylab=expression(delta*theta/delta*h), ylim=c(0,0.03))
ax <- c(1,10,100,1000,10000)
radius <- r(h=ax)
axis(3,at=ax, labels=round(radius,2))
mtext("Equivalent pore radius"~(mu*m),3,line=2.5, cex=0.9)

# End (not run)