2.10.2: Feel and Appearance
- Page ID
- 44337
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)The feel and appearance method also requires the collection of soil samples at the desired depths. The soil sample is crumbled into small pieces and then squeezed by hand to form a ball. The cohesiveness of the ball is an indication of the soil's wetness. Also, whether it leaves an imprint in the palm of the hand after squeezing should be noted. The soil is then ribboned out between the thumb and the forefinger. Table 2.5 provides a detailed explanation of how to interpret the soil water content by the feel and appearance method.
This method requires a great deal of judgement and experience for good estimates of soil water. Nevertheless, it is widely used. Experienced users probably achieve an accuracy of fr plus or minus 0.10. Thus, if estimated fr = 0.55, the true value probably ranges from 0.45 to 0.65. This method is low in cost and allows moisture measurements to be taken quickly at multiple locations in the field. Considering the spatial variability of soil water in a field, the method can be adequate for irrigation management, especially if measurements are checked against a more accurate method periodically. A major disadvantage of this method is the need for experience before confidence is gained and accuracy is achieved.
| Fraction of Available Soil Water Remaining | Loamy Sand or Sand | Sandy Loam | Loam and Silt Loam | Clay Loam or Silty Clay Loam |
|---|---|---|---|---|
| 0 Wilting point | Dry, loose, single grained, flows through fingers. | Dry, loose, flows through fingers. | Powdery dry, sometimes slightly crusted but easily broken down into powdery condition. | Hard, baked, cracked, sometimes has loose crumbs on surface. |
| 0.25 | Appears to be dry, will not form a ball with pressure. | Appears to be dry, will not form a ball. | Somewhat crumbly but holds together from pressure. | Somewhat pliable, will ball under pressure. |
| 0.50 | Appears to be dry, will not form a ball with pressure. | Tends to ball under pressure but seldom holds together. | Forms a ball somewhat plastic, will sometimes slick slightly with pressure. | Forms a ball, ribbons out between thumb and forefinger |
| 0.75 | Tends to stick together slightly, sometimes forms a very weak ball under pressure. | Forms weak ball, breaks easily, will not slick. | Forms a ball, is very pliable, slicks readily. | Easily ribbons out between fingers, has slick feeling. |
| 1 Field capacity | Upon squeezing, no free water appears on soil but wet outline of ball is left on hand. | Upon squeezing, no free water appears on soil but wet outline of ball is left on hand. | Upon squeezing, no free water appears on soil but wet outline of ball is left on hand. | Upon squeezing, no free water appears on soil but wet outline of ball is left on hand. |
Note: Ball is formed by squeezing a handful of soil very firmly.