The Wilting Coefficient and Its Indirect Determination

Abstract

An investigation was made to determine whether the wilting coefficient of a soil can be computed from physical measurements of its moisture retentivity. A comparison of the wilting coefficient is made with the moisture equivalent, the hygroscopic coefficient, the moisture-holding capacity, and the mechanical analysis, for a series of soils ranging from sand to clay. From this comparison, a series of linear relationships is established, as expressed in the following equations, which form a means of computing the wilting coefficient when direct determinations are not feasible. \begin{align*}\mathrm{Wilting coefficient} &= \frac{\mathrm{moisture equivalent}{1.84 (1 \pm 0.007)} \\ \mathrm{Wilting coefficient} &= \frac{\mathrm{hygroscopic coefficient}}{0.68(1 \pm 0.018)} \\ \mathrm{Wilting coefficient} &= \frac{\mathrm{moisture holding capacity}-21}}{2.90 (1 \pm 0.021)}\\ \mathrm{Wilting coefficient} &= \frac{0.01 \mathrm{sand} + 0.12 \mathrm{silt} + 0.57 \mathrm{clay}} {1 + 0.025}\end{align*} The second term of the quantity within the brackets shows the probable error of the relationship in each case, and constitutes a measure of the relative accuracy of the different methods.