Soil Texture - Hand Texturing Method
Along with visual estimation of coarse fragment content, this is the most common method of assessing soil particle size distribution. Every practicing soil scientist, agronomist, 24 and forester should be familiar with hand texturing. This method requires frequent “calibration” with samples of known texture, preferably from the region where hand texturing is to be done.
The hand texturing or feel method is a simple and useful way to quickly assess and classify a soil sample's textural characteristics. It requires minimal equipment and when conducted correctly, can enable frequent assessments out on field sites. Being a qualitative method, it doesn't provide exact percentages for sand, silt and clay. However, the accompanying flowchart to the right can enable a fairly accurate reading for those interested in the relative proportions of a sample.
- Soil sample(s)
- Start by taking a small sample of soil (about a teaspoon) in the palm of your hand, careful to remove and discard any large or coarse fragments and organic matter.
- Add a little bit of water at a time until it becomes a workable putty consistency. Soil that's too wet becomes difficult to handle. If it can be rolled easily into a ball, your sample has been adequately moistened. Refer to Figure 1 as a visual aid.
From here, there are several different "tests" you can perform, by using the accompanying flowchart as a guide (Figure 2), or the official Canadian flowchart found on p. 5, HERE.
- Rub the soil between your fingers. If sand is present, it will feel “grainy”: you will be able to feel the individual grains. Determining whether sand constitutes more or less than 50% of the sample is the first decision in the key.
Moist Cast Test
- Compress some moist soil by clenching it in your hand. If the soil holds together (i.e., forms a “cast”), then test the durability of the cast by tossing it from hand to hand. The more durable it is, the more clay is present.
- Moisten the soil thoroughly and compress it between thumb and forefinger. Determine degree of stickiness by noting how strongly the soil adheres to the thumb and forefinger when pressure is released, and how much it stretches. Stickiness increases with clay content.
- Roll some moist soil between the palms of your hands to form the longest, thinnest worm possible. The more clay present, the longer, thinner and more durable the worm will be.
- NOT recommended due to health concerns.
- Work a small amount of moist soil between your front teeth. Silt particles are distinguished as fine “grittiness”, unlike sand, which is distinguished as individual grains (i.e., graininess). Clay has no grittiness.
- Well-decomposed organic matter (humus) imparts silt-like properties to the soil. However, when subjected to the taste test, it feels non-gritty. It is generally very dark in colour when moist or wet, and stains the hands brown or black. This organic matter is not used as a determinant of soil texture; estimates of the silt content of humus-rich mineral soils should be reduced accordingly. If the soil contains more than a few % of organic matter, hand texturing may become unpractical.
- Work a small amount of wet soil between your thumb and fingers. Silt feels slick and not too sticky (i.e., clay) or grainy (i.e., sand); the greater the dominance of a slick feel, the greater the silt content.
- Here is a brief clip describing some of the main processes described above.
Here is a visual comparison of different "Moist Cast Test" results due to varying proportions of sand, silt and clay found in different soil samples:
BC Ministry of Environments, Lands, and Parks and the BC Ministry of Forests. 1998. Field methods for describing terrestrial ecosystems. Land management handbook no. 25. Victoria, BC.