# psd: Soil Pore Size Distribution In soilphysics: Soil Physical Analysis

## Description

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

## Usage

 `1` ```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 <renato_agro_@hotmail.com>

## 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.

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25``` ```# 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) ```

soilphysics documentation built on Jan. 13, 2021, 7:06 p.m.