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  Estimating Soil Moisture Depletion
The chart below is a compendium of years of experience by researchers and consultants.   It is used to gauge soil moisture depletions by observing the look and feel of soil samples.  Many consultants would prefer to work with a sample from a coring tool rather than a screw auger or bucket auger.  The National Resources Conservation Service has published similar guidelines with full-color pictures for some areas.  Check with your local NRCS (the old Soil Conservation Service).
Moisture
Deficiency
in/ft
Coarse
(loamy sand)
Sandy
(sandy loam)
Medium
(loam)
Fine
(clay loam)
(field capacity) (field capacity) (field capacity) (field capacity)
.0 Leaves wet outline on hand when squeezed. Appears very dark, leaves wet outline on hand, makes a short ribbon. Appears very dark, leaves wet outline on hand, will ribbon out about one inch. Appears very dark, leaves slight moisture on hand when squeezed, will ribbon out about two inches.
.2 Appears moist, makes a weak ball. Quite dark color, makes a hard ball. Dark color, forma a plastic ball, slicks when rubbed.
.4 Appears slightly moist, sticks together slightly. Dark color, will slick and ribbons easily.
.6 Fairly dark color, makes a good ball. Quite dark, forms a hard ball. Quite dark, will make a thick ribbon, may slick when rubbed.
.8 Dry, loose, flows through fingers. (wilting point) Slightly dark color, makes a weak ball. Fairly dark, forms a good ball.
1.0 Lightly colored by moisture, will not ball. Fairly dark, makes a good ball.
1.2 Very slight color due to moisture. (wilting point) Slightly dark, forms a weak ball. Will ball, small clods will flatten out rather than crumble.
1.4 Lightly colored, small clods crumble fairly easily. Slightly dark, clods crumble.
1.6 Slight color due to moisture, small clods are hard. (wilting point)
1.8 Some darkness due to unavailable moisture, hard & cracked clods (wilting point)
2.0 --- --- --- ---