GSIF (version 0.5-5.1)

AWCPTF: Available soil water capacity

Description

Derive available soil water capacity (in cubic-meter per cubic-meter) based on a Pedo-Transfer Function developed using the Africa Soil Profile Database (Hodnett and Tomasella, 2002; W<U+001B3D25>n et al. 2013).

Usage

AWCPTF(SNDPPT, SLTPPT, CLYPPT, ORCDRC, 
    BLD=1400, CEC, PHIHOX, h1=-10, h2=-20, h3=-31.6, 
    pwp=-1585, PTF.coef, fix.values=TRUE, print.coef=TRUE)

Arguments

SNDPPT

numeric; sand content in percent

SLTPPT

numeric; silt content in percent

CLYPPT

numeric; clay content in percent

ORCDRC

numeric; soil organic carbon concentration in permille or g / kg

BLD

numeric; bulk density in kg / cubic-meter for the horizon/solum

CEC

numeric; Cation Exchange Capacity in cmol per kilogram

PHIHOX

numeric; soil pH in water suspension

h1

numeric; moisture potential in kPa e.g. -10 (pF 2.0)

h2

numeric; moisture potential in kPa e.g. -20 (pF 2.3)

h3

numeric; moisture potential in kPa e.g. -31.6 (pF 2.5)

pwp

numeric; moisture potential at wilting point in kPa e.g. -1585 (pF 4.2)

PTF.coef

data.frame; optional conversion coefficients (Pedo-Transfer Function) with rows "ai1", "sand", "silt", "clay", "oc", "bd", "cec", "ph", "silt^2", "clay^2", "sand*silt", "sand*clay" and colums "lnAlfa", "lnN", "tetaS" and "tetaR" (see W<U+001B3D25>n et al. 2013 for more details)

fix.values

logical; specifies whether to correct values of textures and bulk density to avoid creating nonsensical values

print.coef

logical; specifies whether to attach the PTF coefficients to the output object

Value

Returns a data frame with the following columns:

• AWCh1: available soil water capacity (volumetric fraction) for h1;

• AWCh2: available soil water capacity (volumetric fraction) for h2;

• AWCh3: available soil water capacity (volumetric fraction) for h3;

• WWP: available soil water capacity (volumetric fraction) until wilting point;

• tetaS: saturated water content;

References

• Hodnett, M. G., & Tomasella, J. (2002). Marked differences between van Genuchten soil water-retention parameters for temperate and tropical soils: a new water-retention pedo-transfer functions developed for tropical soils. Geoderma, 108(3), 155-180.

• W<U+001B3D25>n, J. H. M., Verzandvoort, S. J. E., Leenaars, J. G. B., Hoogland, T., & Wesseling, J. G. (2013). Soil hydraulic information for river basin studies in semi-arid regions. Geoderma, 195, 79-86.

Examples

# NOT RUN {
SNDPPT = 30 
SLTPPT = 25 
CLYPPT = 48 
ORCDRC = 23 
BLD = 1200 
CEC = 12 
PHIHOX = 6.4
x <- AWCPTF(SNDPPT, SLTPPT, CLYPPT, ORCDRC, BLD, CEC, PHIHOX)
str(x)
attr(x, "coef")

## predict AWC for AfSP DB profile:
data(afsp)
names(afsp$horizons)
## profile of interest:
sel <- afsp$horizons$SOURCEID=="NG 28440_Z5"
hor <- afsp$horizons[sel,]
## replace missing values:
BLDf <- ifelse(is.na(hor$BLD), 
   mean(hor$BLD, na.rm=TRUE), hor$BLD)
hor <- cbind(hor, AWCPTF(hor$SNDPPT, hor$SLTPPT, 
  hor$CLYPPT, hor$ORCDRC, BLD=BLDf*1000, hor$CEC, 
  hor$PHIHOX))
str(hor)
# }