Soil Composition - %Sand %Silt %Clay

15 years ago

Hello all,

I am in the process of getting my soil tests done, but opted to do my own physical analysis rather than pay $27 to have the lab do it. So, using the standard Mason jar soil test (as outlined in the link below) I have some results and wanted to confirm with everyone that I am in the right neighbourhood. Here are the results after 12 hours:

My analysis puts it at:

Total height: 3" (estimate after all has settled in a few days)

Sand: 1.875"

Silt: 1"

Clay: 0.125" (estimate after all has settled in a few days)

So, percentage wise, I think I'm seeing the following:

Sand/Silt/Clay: 63% - 33% - 4%

Consensus?

Thanks for the help,

Michael

Here is a link that might be useful: Soil Test Method

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Comments (8)

Dan _Staley (5b Sunset 2B AHS 7)
15 years ago
That was a fun settling pattern near the bottom there. Yup, looks close just eyeballing it and no math before fully caffeinated. Looks like you'll be adding OM, but those are good fractions to start.

Dan
Lloyd
15 years ago
Michael

That is such a cool picture! I've marked it as a fave.

Sorry, can't offer much on the substance of your question. I'm more of a "rip the ground up with a cultivator, chuck the seeds in and fugetaboutit" kinda guy.

But I think I just might try that test (if the snow ever melts and the ground thaws out).

Lloyd
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piedmontnc summed things up rather nicely but I'll just chime in with this: When testing something, isn't it counter-intuitive to introduce additional ingredients? : Actually, the majority of lab work is done by adding other ingredients. As we've been discussing, a deflocculating agent is added for the textural analysis. In regards to the chemistry portion, the lab has to knock stuff off of the surface of soil particles so that they can be measured by machines, which is done by adding a lot of different stuff, depending on your needs. Sometimes it's an acid, sometimes it's a chelating agent, sometimes is bicarbonate, sometimes it's a cocktail of reagents,etc. Many times, something is detected and measured through a titration in which you keep adding a chemical to a solution until you get the expected reaction and the amount of the chemical that you used tells you how much of the thing you are looking for is in the solution. Lab work is all about adding stuff to what you're testing. Arsenic - strikes me as ubiquitous from the get-go. Yes, it is. How much is too much? That's the sixty-four thousand dollar question and the answer depends on a number of factors. Are you concerned with human exposure to the soil? Plant toxicity? Toxicity to you due to uptake of arsenic by the plants? Ground water contamination? All of the above? Because they will all have different thresholds. Then the answers depend on a whole slew of things including, but not limited to, depth to the water table, soil texture, organic percent, soil pH, the form that the arsenic is in, what you're growing and on and on. Again, I don't think that every time someone uses ironite an angel cries or anything. I just think that there is an, as yet to be determined, potential for crossing one of those thresholds. When there are other options available, I tend to take the cautious route. That's just how I roll. kimmsr and since the professor of soil science I long ago got this simple test from stated that nothing exceopt the soil and water needed to be added to get a good result I've met some brilliant soil science professors, some that pretty much know what they're talking about and some that I have an urge to call after every good rain just to make sure they didn't drown while looking up to see what was falling on them. Don't be too star struck by the title "professor". I see no reason to add anything to flocculate or hold in suppension I know ya don't, buddy. I know ya don't.
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It seems that I will have to just try tilling together some sand and clay to see what effect that has on compaction, and the ability to loosen the soil mechanically (using a tractor, most likely). Now if only it would rain, so the soil was workable... FWIW, this is purely a soil structure question, it really has nothing to do with organics. I don't *want* anything to grow in this particular area, I do want the soil to drain well and not be like an adobe brick. At present, there is sand on top of a clay base. When its wet, its actually kind of slick. The sand drains, the clay at the interface holds tooo much water and that clay/sand interface creates slippery conditions. Cheers, Michelle
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Lots of good replies here. In a nutshell: Sand is weathered rock. Tiny little pieces of rock, broken down by wind and rain and erosion. Silt is weathered sand. These are primary minerals, broken down rock. Clay is different. Clay is a secondary mineral, created from the chemicals given off by sand and silt as they break down into smaller particles through exposure to acids like acid rain or organic acids. Clay particles are tiny plates that fit together very tightly and are attracted to each other by electrostatic charges. Time is the main difference. It takes longer for clay to form than either of the others. Sand, silt and clay are moved around by wind, water and ice. Vermont is rocky because it was scraped bare by glaciers and has not had time yet to develop new soil. Same thing where I am, in the Puget Sound area which was carved out by glaciers. Our soil is what the glaciers dumped as they melted off after carving out Puget Sound and the Strait of Georgia and Hood Canal. It's like gardening in aquarium gravel. Rocks, gravel and sand. No organic matter. I wish I had clay. The river valleys have really nice loamy soil, because they get what's washing down off the mountains - organic matter from the forests, clay from weathering, volcanic ash off Mt Rainier and Mt St Helens etc, and not least, thousands of dead salmon every fall. Migrating salmon returning from the oceans, going up the rivers, spawning and dying and washing up on the banks. The best fertilizer on earth. Prairie soils develop when thick grasses trap wind blown silt and clay. A nice loamy mix of organic matter and soil. Clay soil is what it is. Best to learn to work with it, not against it. You can't change it, only replace it in small areas. Organic matter disappears because the soil microbes eat it. The sand disappears because it gets lost in the clay matrix and sets like concrete. Clay soil is much more fertile than what I have. Clay particles have a very large surface area to volume ratio, so nutrients have lots of surface area to stick to, and stick they do because clay particles are electrostatically charged. In my gravelly soil nutrients wash right through, there's no clay or organic matter for them to stick to. Sand and gravel have no electrostatic charges. All you need to do is add compost and mulch every year. If you have a good worm population they'll work it in. When I had clay I did dig in organic matter whenever planting something not native to the area, and then mulched every year. But if you add a lot of amendments to a hole in clay, you're just creating a clay pot and the plant can drown because water won't drain from the amended soil into the clay. Just add a little bit in a big hole.
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I'm not sure exactly what part you're saying is mythical. From what you've posted: "Coarse Sand or Gravel Subsoil Fine soil overlaying coarse sand or gravel subsoil must become very wet before water will move down through the large pours of the subsoil. Under these conditions, the overlying soil holds up to two or three times as much water as it would if the course subsoil were not present" And that's exactly what I was talking about. The water "perches". It's not actually 100% saturated but it is water that is perched until you apply enough for gravity to suck it down into the subsoil. With proper irrigation management, you can perch the water where you want it and use that effect to your advantage. Of course, that saturated zone (not actually 100% saturation but close enough for the girl's I go with, as my grandfather use to say) Will be bigger in a fine soil over gravel due to greater capillary action but it will still be there in a sand over gravel. You might have a 5 or 6 inch layer of saturation in a heavy soil over gravel and a 1 or 2 inch layer in a sand over gravel. In the paragraph above that, your reference states (when placing a find soil over sand): "When water passes through a fine layer and reaches a layer of coarse sand, it stops until enough water accumulates to nearly saturate the fine soil" Note the use of the word "stops". Again, this happens when going from a sand to a gravel due to a difference in capillary action of the two different layers. Again, this is the effect that we use to "perch" water where we want to so the roots can get to it. As far as a clay layer goes, you're right. You can perch water that way too. "Clay Layer When water reaches the clay, the very fine pores of this layer resist water flow. Although water does pass through the clay, it's penetration is so slow that water tables often build up above the clay." In that condition, note that water actually moves but slowly rather than coming to a dead stop like it does when you put a finer material over a coarser material as discussed previously. However, your zone of saturation will be larger and you can't "push" water into the subsoil when you need to by applying a bigger head of water. It will just perc as slow as the clay will allow it to move and no faster. It's harder to control soil moisture that way. Both of these conditions become less and less important the deeper in the profile the textural interface is but when the interface exists relatively near the surface, either by accident or design, it can be an advantage or a liability depending on intent and management practices. ("Or so the legends of yore go.", I suppose I should say)
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hamiltongardener
15 years ago
Does that layer seem to be over the 2 inch mark to anyone else, or just me? Maybe my eyes are worse than I thought.

Maybe Kimmsr should take a look at it and give an analysis.
Dan _Staley (5b Sunset 2B AHS 7)
15 years ago
Does that layer seem to be over the 2 inch mark to anyone else, or just me? Maybe my eyes are worse than I thought.

Close-ish, sure enough. But its still a sandy loam that needs OM, as there's very little darkening in the profile and the water is light-colored. That's a thin clay layer so your CEC is possibly low too, in addition to low WHC so Michael has some digging and turning to do. But its a decent soil to start with.

Dan
Kimmsr
15 years ago
The math is a lot easier if you use 4 inches of soil in that 1 quart jar since all you need do is divide the level of each part of the soil by 4 to get the percentages. With 3 inches there are conversion factors that need to be used.
Sand, the largest and heaviest soil particle, will settle to the bottom while silt, lighter and smaller in size, will be next, and clay, the smallest and lightest, will be above those. However this is most useful for organic matter which will float on top and you have no organic matter in that soil sample.
What I see in your sample tells me that you have about equal amounts of sand and clay and a lot of silt. The level of sand is about 7/8ths of an inch, your silt is about 1-1/4 inch, and the clay is about 3/4 inch.
Dan _Staley (5b Sunset 2B AHS 7)
15 years ago
Interesting.

From here with no magnification I see two size classes of sand and two size classes of silt. Not knowing anything about the soil, I'd guess the bottom striated layer ending at ~7/8 has some sort of iron-rich mineralization in it, making it settle first, being heavier than quartzite-types. Around 1.75 inches we see interdigitating of silt and sand.

I'd be happy to be corrected, as I haven't done soil analysis outside of my/client's garden for well over a decade, and this largely on very old soils that I knew well, not these glaciated-types.

Dan
m_lorne
Original Author
15 years ago
Sorry everyone, what you are seeing from the bottom to the 7/8" line is actually the reflection of a wood grain desk. LOL Sorry, guess I should have mentioned that!

Since taking the photo, I have had another 1/4" settle, which is probably 1/8" clay, and 1/8" OM.
Dan _Staley (5b Sunset 2B AHS 7)
15 years ago
haha - funny. I should say my Red Wings sweatshirt is reflecting on the screen tinging the bottom layer red and making me think of iron and glaciers...

Nonetheless, still looks from here like sandy loam with very little OM and the other stuff I said upthread.

Dan

Soil Composition - %Sand %Silt %Clay

Comments (8)

Dan _Staley (5b Sunset 2B AHS 7)

Lloyd

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Dan _Staley (5b Sunset 2B AHS 7)

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