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Soil STRUCTURE

Posted by piedmontnc 7b-8 (My Page) on
Thu, Apr 1, 10 at 19:33

Since this is the soil forum and all...
A certain poster, we'll call him 'K', keeps posting this bad information

1) Structure. From that soil sample put enough of the rest to make a 4 inch level in a clear 1 quart jar, with a tight fitting lid. Fill that jar with water and replace the lid, tightly. Shake the jar vigorously and then let it stand for 24 hours. Your soil will settle out according to soil particle size and weight. A good loam will have about 1-3/4 inch (about 45%) of sand on the bottom. about 1 inch (about 25%) of silt next, about 1 inch (25%) of clay above that, and about 1/4 inch (about 5%) of organic matter on the top.

Which according to the practice of SOIL SCIENCE, is completely wrong! The percentage of sand, silt, and clay fractions is know as TEXTURE.

STRUCTURE is the how soil peds aggregate, with a few examples being blocky, columnar, single grain, etc.

http://soils.usda.gov/technical/fieldbook/

Now back to your regularly scheduled program


Follow-Up Postings:

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RE: Soil STRUCTURE

  • Posted by pt03 3 Southern Manitoba (My Page) on
    Thu, Apr 1, 10 at 19:54

:-)

Ya, personally, my forehead is too sore. Other than the incorrect terminology, are the numbers correct? I'm way too lazy to do the research myself and the efficient way would be to just ask someone who actually knows this stuff.

Hey! Laziness breeds efficiency! ;-)

Lloyd


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RE: Soil STRUCTURE

The percentages are pretty much correct, except %OM isn't considered so 5% is missing in the mineral fraction.

Here is a link that might be useful: Soil Textural Classes


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RE: Soil STRUCTURE

  • Posted by pt03 3 Southern Manitoba (My Page) on
    Thu, Apr 1, 10 at 20:04

So OM isn't considered in the basic textural classification of the soil?

Lloyd


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mineral soils are different than organic soils

For mineral soils, no.


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RE: Soil STRUCTURE

Back when I did this in the lab we dissolved the organic content with concentrated peroxide before screening to determine sand silt and clay fractions. Some of my salt marsh samples had almost nothing left once the organic matter was removed.


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decomposing OM

My soil taxonomy book has a great picture of a septic tank fully exposed that was originally underground in an organic soil. When the water table was lowered, the OM decomposed leaving the tank high and...er 'dry'.


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Mineral versus Organic??

  • Posted by pt03 3 Southern Manitoba (My Page) on
    Thu, Apr 1, 10 at 20:19

I wasn't aware of the distinction between mineral and organic soils. Mind you, what I know about the science of soil wouldn't get me past the first level of "So you think you're smarter than a 5th Grader".

Okay, there's words in here that I've never even seen before!! pumiceous?? paralithic?? Clearly my 45 minutes of university education is insufficient for this task.

Maybe I oughta stick to composting.

Lloyd

P.S. I am going to read that document, but not tonight.


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pumas

Pumiceous-being composed of partially decayed pumas

<.< >.>


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pumas

  • Posted by pt03 3 Southern Manitoba (My Page) on
    Thu, Apr 1, 10 at 20:26

Pumas?? Are they like, cougars??

Lloyd


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mmmm cougar

Only if they're man-eaters...


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RE: Soil STRUCTURE

Actually they're referring to soils comprised primarily of decomposed:


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RE: Soil STRUCTURE

Here I imagined Pumiceous sounded like lava [lavish?] soils.


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RE: Soil STRUCTURE

Exactly Wayne,
I have very (Pumice)= Lavish Soil ;-)

Awesome Soil 3-10-2010

Here is a link that might be useful: Wonderful Soil


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RE: Soil STRUCTURE

Actually there is no reason to attempt to disguise the person you are writing about, but as I have told you before those soil tests were gotten from a soil scientist many years ago and several soil scientists since then tell me that they have no problem with that description and probably the only people that would would tend to be Obsessive Complusive.
I realize there are many people that feel strongly that there is no need to look at your soil, however, knowing about your soil, what is in it, what it feels like, how well it drains, etc. is kind of like being a high school dropout or continuing on the complete high school or college. Knowing about your soil is a tool that can be used to help guide you in making that soil into a good healthy soil that wil grow strong and healthy plants that are better able to ward off insect pests and plant diseases.


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riiiight

IOW, you're not interested in using correct terminology and anyone who points that out is the OC one.


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RE: Soil STRUCTURE

Pick up any soil science textbook and you'll confirm piedmontnc's claims. Nothing's changed......those terms didn't magically develop new definitions overnight. Soil science is what it is :-)

One of the ways back in college we learned to distinguish between the two was that you can alter or change the soil structure but the texture is considered a stable property and is not easily changed. Think about it.......it makes sense!


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RE: Soil STRUCTURE

  • Posted by pt03 3 Southern Manitoba (My Page) on
    Fri, Apr 2, 10 at 11:05

Head + Wall = Ouch

Lol

Lloyd

P.S. Due to this example, as well as others already pointed out in the past few years, I consider everything from this particular source to be suspect.


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RE: Soil STRUCTURE

Ok, now that I've been re-calibrated wrt texture/structure...

Speaking of soil "Texture", there has been several discussions of the risk of adding sand to clay in an attempt to improve its texture. But I haven't seen much discussion of using silt as a method of altering texture.

As I understand it, Sand and silt are very similar in chemical composition and usually contain quartz. Clays (hydrous Aluminum silicates) are different.

My soil has a lot of clay. I'll have to re-run kimmsr's soil texture test to see how much silt and sand are in my soil. My aim is to try to permanently improve the soil texture.

My biggest win in improving my soil seems to come from adding the humic shale ore stuff. It does indeed cause the soil structure to change. I've seen similar results from heavy applications of coffee grounds, and from adding ordinary compost.

Biggest boo-boo? Dumping bone meal on clay. Jeepers, it turns the clay into rock. I could easily make adobe bricks with my clay soil if I do the wrong thing. I have run into hardpan under my yard's soil, stuff that is so hard, my forged steel irrigation shovel bounces off of it. Probably made the same way - too much calcium in the clay. Digging through the hardpan is a matter of chipping it like it was rock. (But I suspect soaking that stuff with the humic shale ore will dissolve the hardpan. I'll have to try that next time I dig into that layer.)

Amazing how we can alter the soil (texture and structure).


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RE: Soil STRUCTURE

You can't alter texture :-) Or not to the point where it is the slightest bit practical to do so.

You can alter structure - that's what amending does in terms of adding OM to loosen and break up heavy soils and improve drainage. Adding silt is not going to accomplish much - the particle sizes are too small to be of any value in flocculating or creating the peds necessary to provide sufficient pore space to loosen and aerate the soil and improve drainage. Even sand is of minimal value unless it is added in very large quantities (recommended at a 1-1 ratio) AND it has a very coarse texture.


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RE: Soil STRUCTURE

Sand, silt, and clay will all be composed of the same stuff, depending upon what the original bed rock or mother rock is. Clay is simply very much smaller particles than silt. Silt is very much smaller than sand. Up from that, but not included in what soil scientists refer to as 'soil' would be gravel, and rocks. Same stuff....different size.

Silt, in terms of understanding the size of the particles, is like a finely ground flour. When wet, you can barely feel it between your fingers. And like flour, it gets muddy and sticky. Scientifically speaking, the grain size of silt ranges from .002 to .05 - a bit weensy to use as an amendment.

The best material for the improvement of a clay soil remains organic matter of almost any kind. But you've already discovered that, Idaho Gardener! Seasonal applications of organic mulch and compost will do much to improve the STRUCTURE of your soil.


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RE: Soil STRUCTURE

My understanding of the differences between silt and clay is different than rhizo's. Clay is created by chemical processes, not mechanical (grinding) processes. As I understand it, clay is chemically different than silt or sand.

I don't understand the assertion that texture cannot be altered. If you mix silt with clay, by the definition of texture, you have changed its texture.

And it is also my understanding that ideal soil, called loam, is a mixture of sand, silt, and clay. A loam can have a predominance of one of the ingredients (sandy loam, clay loam), but any of the loams are a better soil than any non-loam soils.

I think we are all in agreement that organic matter is the important ingredient for soil structure.


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RE: Soil STRUCTURE

Clay is simply very much smaller particles than silt.
Well, not really. Silt and sand particles are just chunks of minerals with no charge, negative or positive.
Clay particles are actually stacks of sheets of oxygen atoms and/or hodroxyl (OH) anions (octahedral sheets and tetrahedral sheets) with other atoms sandwiched in the sheets.
When the atoms in the sheets are replaced by atoms of similar size but a lower positive charge, the clay particles take on a negative charge. A common example is the replacement of a silicone atom with a charge of 4+ with an aluminum atom with a charge of 3+, resulting in a net negative charge.
So, are the same atoms involved? Sure, quartz will be made of silicone and oxygen and some clays are a latticework of oxygen atoms with silicone sandwiched in there. But they are very different structurally and in the way they behave. That's why cation exchange capacity is dictated largely by the clay content; because the nature of clay is what gives it the negative charge which is the ability to attract and hold on to cations. Neither sand nor silt has that property.
I would be happy to provide more details if you like, but I'm working really hard on being less wordy. (and only half succeeding I'm afraid).


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RE: Soil STRUCTURE

I don't understand the assertion that texture cannot be altered. If you mix silt with clay, by the definition of texture, you have changed its texture.

Theoretically, you are correct :-) And while this can be done rather easily with a small sample, it is just not practical to attempt on any kind of large scale. The quantities of material involved are just too great to be able to effect a significant change.

Without going into all the technicalities of soil science, just do a Google search on "changing soil texture" and see what you turn up. Virtually every site will make statments such as these:

"The texture of a soil is a permanent characteristic. It is a direct reflection of soil parent material and long weathering processes. Soil management practices do not change soil texture."

"Soil texture measures the size of the particles that make up your soil. Given that it took several millennia for these particles to reach the size they now are, this is not one of the things you can easily change in your soil."

"The texture of soil is considered to be a stable property. That is, changing the texture of your soil is possible but involves considerable mechanical and financial input."

"The texture of a soil is permanent, the farmer is unable to modify or change it."

"Soil texture is an inherent soil property that you as a gardener cannot change (except through extreme interventions)."


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RE: Soil STRUCTURE

Gardengal wrote " "Soil texture is an inherent soil property that you as a gardener cannot change (except through extreme interventions)."

That's me ;-)

Extreme Interventionist ;-)

and I agree also with " involves considerable mechanical and financial input."

3'  deep tilling


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RE: Soil STRUCTURE

English translation of clay vs. sand: First Rizo is sort of right, but wrong about clay particles. Sand and clay are not technically the same just different size particles. Rizo is correct in the sense that the underlying bedrock will determine the mineral makeup in a particular location, however, gargwarb is correct about the molecular structure of clay. Basically, all sands are fine particles of silica; they are granular. Clay, on the otherhand is made up of numerous different minerals, depending where in the world you are.

To translate garbweb, and explain why clay and sand are not the same, simply put, individual grains of sand do not attract other minerals because they are negative. That is why you can only shape sand when it is wet, but not when it is dry; that is why sand does not wick water into other objects. Think of sand grains like mini reflecting balls. That is why sand is pure silica (it doesn't bond to the other minerals).
When you add sand to Portland cement the sand is not attracting the cement, rather the cement is surrounding and trapping the sand particles inside; the cement is doing the attracting, which is why it must be thoroughly mixed to be strong.

Clay, on the otherhand often has a high silica content, but instead of being made up of little grains it is actually a minute and complex network of platelets that bond together. Therefore, whatever minerals are in the bedrock will be present and trapped in the clay and extremely difficult to break apart unless it is bone dry and crushed or turned to complete liquid. That is why adding sand to clay creates a form of (natural) concrete. If you add a little bit of sand the clay bonds to it and gets even harder; if you add more sand than clay it will be more crumbly. Clay is like a natural glue. Think of clay platelets like millions of tiny fingers or webs locking together.

BTW: Quartz is Silica, so the different colors of sand come from the different colors of quartz that were weathered away over time.


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RE: Soil STRUCTURE

  • Posted by pt03 2b Southern Manitob (My Page) on
    Sun, Feb 6, 11 at 0:41

Bump for those that might be interested in the correct terminology and some explanation as to the difference between the two terms.

Some attempts at humour in here too so I hope that doesn't offend anyone. ;-)

Lloyd


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RE: Soil STRUCTURE

Interesting discussion. I am fairly ignorant of the science of soil structure, texture and chemistry but trying to rapidly get up to speed. At least on basic terms.

Speaking of which, 'sand' is strictly a descriptor of particle size, not material composition, correct? Because, for example, my sand soil in central florida is not primarily silica but is calcereous, decomposed shells. My sand soil here in MA is glacial till. Oddly, to my way of thinking, even though the particle size of the florida material is a good deal finer than the rock sand here, the former hangs onto far less OM. Florida gardeners well know that the sand "eats" OM like a dog eats table scraps. I attribute it to the higher average ground and air temps.


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RE: Soil STRUCTURE

Speaking of which, 'sand' is strictly a descriptor of particle size, not material composition, correct?

Correct.


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RE: Soil STRUCTURE

  • Posted by jolj 7b/8a-S.C.,USA (My Page) on
    Mon, Feb 7, 11 at 3:55

If one can lay newspaper on lawn grass & put up 2" x12"'s in a 4' X 8' box that they then full with compost.
Then why can not the same person dig a 4' X 8' X 18" in clay & mix 48 cubit feet of sand to make a raised bed of sandy clay that they can add organic matter to?
Before you said add the organic matter & skip the sand.
The question is why this will not work , not that the om is not or is better. Of all the places in the world, this site agrees that compost or organic matter is always best.
I want to know why the anyone says that sand can not improve clay soil in the above example.


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RE: Soil STRUCTURE

Hey jolj ,
I have a feeling that people are answering in generalities because we have all walks of life on this forum ie..old,infirm,weak....not to mention,overworked and such, that and most people don't have access to large equipment, so ...for example, it would be stupid for me to tell people how to make killer fluffy soil out of clay (like I did) ,when they have no access to an excavator...or for that matter, loads of Decomposed Granite or bulk Pumice. I mean to say, I tell people how I did it, but I don't expect them to be able to pull that off themselves, for the majority of people on this forum, they have a shovel,maybe a pick, so for them ...cardboard over grass and pile on the new soils and after may seasons of adding organic material, they too can be blessed with a great garden bed.


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RE: Soil STRUCTURE

I want to know why the anyone says that sand can not improve clay soil in the above example.

It potentially can but you're better off improving the soil with OM. There's a world of difference between a sandy clay with blocky structure and a sandy clay with massive structure. If you can mix the sand into the clay and avoid creating massive structure then go for it.


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RE: Soil STRUCTURE

I tell people how I did it, but I don't expect them to be able to pull that off themselves

You know, jonhughes, I actually thought you did expect us to all run out and do it, and I've been sitting here thinking, "Man, he's crazy!"


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RE: Soil STRUCTURE

piedmontnc,

I agree that organic matter is needed in large quantities when mixing sand into clayish soils. With my clay loamish soil I mixed large amounts of sand, local peat moss, and other organic matter. It all reminds me of John Hughes' picture of digging into his elbows...love it.


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RE: Soil STRUCTURE

  • Posted by jolj 7b/8a-S.C.,USA (My Page) on
    Fri, Feb 11, 11 at 19:28

John, I summit to the Master! As I have said before you are right & I want your set up for fathers day, birthday & Christmas.
wayne, Thank you, that is what we did for a friend. He had soft soil in winter & rock hard in summer. Now he has clay loam & continue to add compost. We could get coarse sand cheap. The stuff that was called topsoil (meaning rich)was closely & just mud & half decade sticks( swamp dirt, not even soil). So we added the sand,4 tons in one weekend & cut it in. He has spent the last 24 months adding compost & leaves/yard waste, as he finds it.
The plot is looking better every year. Sheet composting is a beautiful thing.


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