Soil moisture measurements
Two common ways to estimate the soil water deficit are by the feel and appearance method or using soil water sensors. Here we describe how to use the feel and appearance method.
Feel and appearance method
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Collect soil samples in the root zone with a soil probe or spade.
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Estimate the water deficit for each sample by feeling the soil and judging the soil moisture as outlined in Table 1.
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Take soil samples at several depths in the root zone and at several places in the field.
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Use these estimated deficits to estimate the total soil water deficit in the root zone.
This method requires frequent use to develop consistent estimates.
Table 1. Guide for judging soil water deficit based on soil feel and appearance by soil texture.
| Moisture deficiency | Coarse texture (loamy sand) AWC=0.6-1.2 in/ft |
Sandy texture (sandy loam) AWC=1.3-1.7 in/ft |
Medium texture (loam) AWC=1.5-2.1 in/ft |
Fine texture (clay loam) AWC=1.6-2.4 in/ft |
|---|---|---|---|---|
| 0.0 inches per foot (field capacity) | 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 hands when squeezed, will ribbon out about two inches |
| 0.2 in./ft. | Appears moist, makes a weak ball | Quite dark color, makes a hard ball | Same as above | Same as above |
| 0.4 in./ft. | Same as above | Same as above | Dark color, forms a plastic ball, slicks when rubbed | Dark color, will slick and ribbons easily |
| 0.6 in./ft. | Appears slightly moist, slightly sticks together | Fairly dark color, makes a good ball | Same as above | same as above |
| 0.8 in./ft. | Appears to be dry, will not form a ball under pressure | Slightly darker color, makes a weak ball | Quite dark, forms a hard ball | Quite dark, will make a thick ribbon, may slick when rubbed |
| 1.0 in./ft. | Same as above | Lightly colored by moisture, will not ball | Fairly dark, forms a good ball | Fairly dark, makes a good ball |
| 1.2 in./ft. | Dry, loose, single grains flow through fingers (wilting point) | Very slight color due to moisture, loose, flows through fingers (wilting point) | Slightly dark, forms weak ball | Will ball, small clods will flatten out rather than crumble |
| 1.4 in./ft. | -- | Same as above (wilting point) | Lightly colored, small clods crumbles fairly easily | Same as above |
| 1.6 in./ft. | -- | -- | Same as above | Slightly dark, clods crumble |
| 1.8 in./ft. | -- | -- | Slight color due to moisture, powdery, dry, sometimes slightly crusted but easily broken down in powdery condition (wilting point) | Some darkness due to unavailable moisture, hard baked, cracked, sometimes has loose crumbs on surface (wilting point) |
| 2.0 in./ft. | -- | -- | -- | Same as above (wilting point) |
For additional information, see Estimating soil moisture by feel and appearance from NRCS.
Acknowledgements
The author wishes to thank former University of Minnesota colleagues Joshua Stamper and Jerry Wright for their previous development efforts in earlier iterations of this content.
Reviewed in 2019