Soil Pore Size Distribution
The unimodal soil pore size distribution based on van Genuchten's model.
psd(thetaS, thetaR, alpha, n, h)
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. |
A numeric vector containing the soil pore size distribution as a function of soil water tension.
Renato Paiva de Lima <renato_agro_@hotmail.com>
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.
# 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)
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