Description Usage Arguments Details Value Author(s) References See Also Examples

An interactive graphical adjustment of the soil water retention curve via the van Genuchten's formula, modified by Pierson and Mulla (1989). The nonlinear least-squares estimates can be achieved taking the graphical initial values. It may be useful to estimate the parameters needed in the high-energy-moisture-characteristics (HEMC) method, which is used to analyze the aggregate stability.

1 | ```
fitsoilwater5(theta, x, theta_S, xlab = NULL, ylab = NULL, ...)
``` |

`theta` |
a numeric vector containing the values of soil water content. |

`x` |
a numeric vector containing the matric potential values. |

`theta_S` |
an offset; a value for the parameter |

`xlab` |
a label for the x axis; if is NULL, the label "Matric potential" is used. |

`ylab` |
a label for the y axis; if is NULL, the label "Soil water content" is used. |

`...` |
further graphical arguments; see |

The parameter theta_S must be passed as an argument. It is recommended to consider it as the highest water content value in the data set or the water content at saturation.

A plot of `theta`

versus `x`

and the curve of the current fitted model
according to the adjusted parameters in an external interactive panel.
Pressing the button "NLS estimates" a `nls`

summary of the
fitted model is printed on console whether convergence is achieved, otherwise
a warning box of "No convergence" is shown.

Anderson Rodrigo da Silva <anderson.agro@hotmail.com>

Pierson, F.B.; Mulla, D.J. (1989) An Improved Method for Measuring Aggregate Stability
of a Weakly Aggregated Loessial Soil. *Soil Sci. Soc. Am. J.*, 53:1825–1831.

1 2 3 4 5 6 7 8 9 10 11 | ```
h <- seq(0.1, 40, by = 2)
w <- c(0.735, 0.668, 0.635, 0.612, 0.559, 0.462, 0.369, 0.319, 0.296, 0.282,
0.269, 0.256, 0.249, 0.246, 0.239, 0.236, 0.229, 0.229, 0.226, 0.222)
plot(w ~ h)
# suggestions of starting values: thetaR = 0.35, alpha = 0.1, n = 10,
# b0 = 0.02, b1 = -0.0057, b2 = 0.00004 (Not run)
fitsoilwater5(theta = w, x = h, theta_S = 0.70)
# End (Not run)
``` |

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