DIY Texture analysis results

8 years ago

last modified: 8 years ago

It’s interesting how we seem to assume any time a soil is a little hard to dig, it’s “clay” – when my DIY soil texture analysis says otherwise. I did the mason jar test – put some soil and water in, shook it up, and let it settle.

I dug two samples – one from the clearly sandier part of the yard, and one from the rock-hard stuff that doesn’t crumble from out front, which I always assumed was clay.

The sandy stuff is probably a silt loam ( but closer to the sandy side) or possibly just ‘loam’ – most of the particles settled fast, about 45% sand, a lot of silt, and only a very thin layer of light clay settled out after a few days (less than 5% clay by volume).

The “clay” is actually mostly silt – also less than 5% clay, about 25% sand, so probably a silt loam, or maybe just silt, per the triangle. This is definitely a heavier soil, and stays moist even weeks after a good rain, even in summer, and is a dark grayish color.

The sandier silt loam is a light-medium brown. It doesn’t dry out all that quickly, for being as sandy as it is, but definitely doesn’t stay moist as long as the siltier stuff.

It’s odd how two soils that technically probably fall in the same part of the triangle, are so different. I currently marked up the triangle below approximately where I think the two samples fall.

Featured Answer

rhizo_1 (North AL) zone 7

8 years ago

I'm concerned about the accuracy of your method.

Did you omit the powdered washing soda, like Arm and Hammer laundry booster? That ingredient is necessary for the particles to properly disperse....water alone will not do the job. Dish soap works as a dispersal agent but the suds can work against you.

Did you remove the top couple of inches before taking your sample? Are you removing a sample from as deep as six inches or more? And did you screen out the pebbles, roots, and other big stuff? After you've collected and prepared the sample, stir it up well before starting your procedure.

Optimally, use a clean quart jar with even, smooth sides and fill one third of it with your soil. Fill the jar with water and about a teaspoon of the washing soda.....and shake well for a minute or two, making sure that all of the powder is dissolved.

Here's the hard part:

Let the jar SIT quietly for twenty four hours without disturbing it. It can really take that long for the microscopic clay particles to precipitate out of the solution.

I'm afraid that there are websites that give instructions without the washing soda or soap, but your results can vary widely if you don't follow the scientific protocol for this very simple test.

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Comments (6)

hairmetal4ever
Original Author
8 years ago
Thank you. I’ll try it again.

Would Borax work?
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hairmetal4ever
Original Author
8 years ago
Redid it with dish soap. This is the “heavier” sample. The red line is where the sand is, most of the rest is silt. All the clay hasn’t settled yet, but there doesn’t appear to be much.
kimmq
8 years ago
In some 50 years of using that soil test I have not found any difference in samples that used a soap as a dispersant and others with no soap. The soil scientist that first clued me in to that soil test did not use soap and told me that soap was not necessary.
toxcrusadr
8 years ago
Washing soda is actually sodium carbonate, which is highly alkaline but not actually a detergent. I have not heard of this myself but I confess I have never done this test on my own soil so I don't profess to be an expert. I would like to understand how it is purported to work though. Soil particles do aggregate. If they are aggregated by the action of soil organic matter, either detergent or alkali should help to dissolve organic matter and maybe that's how it works. I have an open mind on this one until I understand it better.
gardengal48 (PNW Z8/9)
8 years ago
Plain old baking soda will do the same thing........it is something about the chemical properties of the sodium and its effect on the clay that allows the particles to precipitate out completely = prevents flocculation.

Interesting that when in college, my soil science professors never included that ingredient (or dish soap) in the jar test. And we all got satisfactory results. I don't use it for my soils classes either. Might make very good sense in those areas that tend to have heavy clay soils, however.