soil types

Discussion in 'Planting, growing, nurturing Plants' started by pebble, Jul 11, 2009.

  1. pebble

    pebble Junior Member

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    I'm doing that soil in a jar of water test that Rosemary Morrow suggests. I'm not clear on what's going on though. Is silt the same as clay?

    The soil I have seems to be both gritty (has lots of small gravel in it) and silty (the water is still cloudy after several days), although the silt layer on it's own is quite thin.
     
  2. ecodharmamark

    ecodharmamark Junior Member

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  3. SueinWA

    SueinWA Junior Member

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    Re: soil types

    The 'jar test' doesn't really measure organic matter, just the mineral soil parts. When you do this test, scrape off about the top 2" (50mm) of soil and set it aside (it contains the highest percentage of organic matter in most soils). For your sample, take it from the next 4" (100mm) down. Your jar (quart/litre size) should have about 2" (50mm) of soil, fill the rest with water. (Some people say to add a spoonful of detergent, table salt or water softener salt to the jar -- I should try that sometime... )

    Do your best to pick out the stones and pebbles.

    Small pebbles hit the bottom first, then coarser sand, then silt (a mineral soil that is finer than sand, but not as fine as clay). Measure the sand layer after one minute, the silt layer after two hours, and the clay layer after several days (don't bother waiting for it to clear completely, some will stay in suspension). If you've got stuff still floating on the surface, that's probably some organic matter, and you don't include it in this test.

    If you can measure the layers fairly accurately, use the information on this page to calculate what kind of soil you have: https://www2.ville.montreal.qc.ca/jardin ... al_eau.htm

    You will need to have a professional soil test to find out what percentage of organic matter your soil contains.

    Sue
     
  4. gardenlen

    gardenlen Group for banned users

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    Re: soil types

    g'day pebble,

    silt forms clay as it is erroded from higher up to the lower down stratas. that is why the caly contains so much of its own nutrient but locked up and that is why we add in gypsum to help condition that clay for the plants benefits. also why we use raised beds so that soil can be changed over time by the worms and micro-organisms we attract into our medium.

    so not sure why you are doing the water test? but that is one way to test for you clay type in case you have clay that will not respond to gypsum. so without any testing if you simply add in organic mater or use raised beds you are on your way to success.

    len
     
  5. pebble

    pebble Junior Member

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    Re: soil types

    Thanks everyone.

    The reason I am doing the test is because I am wanting to learn about different soils in different places. This is one of the things I am doing for that. The current jar has soil from a nearby paddock, not from my garden.

    I'm thinking the water jar test will help me understand soil structures, and that I'll be able to compare what I learn from the jar with what I see in the ground.

    Where I got a bit confused was what I have in the jar didn't easily match what Morrow described.

    The whole jar is grey. There is a very thin layer at the top of the solids, very silky. Below that is a larger layer that is also silky but increasingly has bigger particles as it goes down. I'm assuming that is a mix of silt and gravel. There is a small layer at the bottom with the biggest particles in it (small gravel).

    I just wasn't sure if silt was a specific material, or if silt could be a number of things but simply described the texture and fineness of the material.

    And I still don't know what is in my jar! (apart from gravel at the bottom, and some organic material floating at the top). I'm guessing no clay, much silt and a bit of sand.


    So would the silt I have be closer to sand, but other soil might have silt closer to clay? How do I tell? Would the very thin layer at the top be clay not silt? How would I tell?
     
  6. ecodharmamark

    ecodharmamark Junior Member

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    Re: soil types

    G'day again, pebble

    Sorry, I should have been more specific. If you click on the following link (part of the earlier website I provided) you will see a graph that clearly shows the breakdown of soil mineral componants:

    https://www.landfood.ubc.ca/soil200/comp ... le_pix.htm

    I hope this is what you are after, and that it helps you to understand the difference (in particle size) between clay, silt, sand and gravel.

    As previously mentioned, the UBC Soil site is a brilliant resource, and if you really want to understand your soil (in all of its facets), you could do a lot woese than spend some time studying it.

    Cheerio, Mark.
     
  7. pebble

    pebble Junior Member

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    Re: soil types

    Thanks Mark :) That's a good chart. I got a bit bogged down elsewhere on that site (it was more technical than I needed) but will come back to it when I've got the basics sorted.

    I think I've always assumed clay was a certain kind of material (or materials). But that chart is implying that the difference between clay and silt and sand and gravel is simply to do with size of particles. They could all be the same material. Is that right?
     
  8. ecodharmamark

    ecodharmamark Junior Member

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    Re: soil types

    G'day pebble

    Try this:

    Soil is essentially made up of 4 componants (as graphically depicted on the very first page of the very first link I provided):

    Mineral/s ('rock') - gravel, sand, silt and clay (as determined by their particle size), and yes, they COULD be made up of all the same base material, but likewise they COULD by made up of a combination of whatever base materials have positioned themselves in the particular spot you are testing. Generally speaking, these 'little rocks' (gravel, sand, silt and clay) have emerged as a process of weathering, and have either been deposited through the actions of sedimentaion (such as on an aluvial flood plain), or by the means of some other geological process - volcanic activity, for eample. Crikey, they may have even been dumped there as 'fill', and may have originated from the other side of the world!

    Organic matter - 'alive' (the little micro-organisms (biota) that live in the soil), and 'dead' (the vegetative material that is the detris of plant life).

    Water

    and

    Air.

    By scooping up a couple of handfulls of soil, you have by chance collected any or all of the above, in an infinately variable combination (isn't 'nature' grand?). By placing this collected material in a jar of water, you have effectively displaced all of the air. So put 'air' asside for the moment as a componant of your soil sample.

    Likewise, forget the 'water' componant, pretend it isn't there. In a lab, when a soil compostion test is conducted, all of the 'water' is taken out of the sample via heat treatment - effectively, it is put in an oven. Of course this kills all of the biota, but that is another story...

    Now, back to your sample of 'soil in a jar of water':

    What you most likely have is organic material floating on top? For the purpose of the exercise, disregard this material (as Sue in WA suggested), as what I think you are trying to do is determine the varying amounts (by particle size) of mineral/s ('little rocks') in your soil?

    Anyway, by disregarding air, water and organic matter, what you have left is mineral content. This should appear as 'strata' (individual layers)? Gravel on the bottom, then sand, then silt, then clay (assuming that you have all of these mineral particulate sizes in your sample)?

    Essentially, this test is designed to see (at a glance) the amount/s of gravel, sand, silt and/or clay you have in your soil, and in proportion to each other.

    I hope the above helps, and yeah, the link I provided is a bit heavy in places, but the 'basics' are all there. As I always say to my fellow students: "The answers are there, you just have to find them, and in order to do that, you just have to READ".

    Let us know how you get on.

    Cheerio, Mark.
     
  9. pebble

    pebble Junior Member

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    Re: soil types

    That's great Mark, I get it now, thanks! Sometimes you just can't beat talking to someone who already knows ;-)

    Why should I ignore the organic matter in the jar?

    I think the jar has a very small line of clay in it. I did a second jar with soil from ten metres away, and it's fairly similar but it's brown instead of grey. That would mean similar structure but different minerals yeah? Or is it more organic content? The first jar is probably from beside an old stream or watercourse, the second one is from a rich patch of grass (the lushest in the paddock).
     
  10. ecodharmamark

    ecodharmamark Junior Member

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    Re: soil types

    G'day pebble, mate :D

    For the purpose of the tests that you have been conducting, which is a basic, quick, cheap and pretty effective way of identifying overall mineral content, and the ratio at which it occurs, within any given sample (remember particle sizes: gravel, sand, silt and clay) of your soil, the organic matter is of no concern (more about that, later).

    Then as you have so rightly presumed, it's a fair bet that the mineral content (both in total volume, and particle ratio) is similar.

    Maybe, and maybe. The colour of soil can be determined by many factors. Yes, the colour of the base mineral content can play a big role in determining the overall colour of soil, and yes, so too can the presence of organic matter. But likewise can the presence of (or lack of) air, and even the presence of water can alter the colour. The latter is usually due to the presence of 'colloids' (tiny suspended particles that will just not settle) in the water.

    Got a job for you to do, pebble. Grab yourself a nice (sharp) shovel, a pick, and maybe a crow bar. I want you to go out into this paddock from which you are collecting your samples, and (carefully) dig a hole. I say carefully because you are conducting another 'test'. Except this time you are not only just concerning yourself with the mineral content and particle ratios (the 'texture') of the soil (as you did with the jar test), this time you are looking at the soil 'profile', and in particular, the differing 'horizons' that occur within the profile.

    Check out this link (yes, from that same web page, and yes, more cool graphical stuff):

    https://www.landfood.ubc.ca/soil200/clas ... orizon.htm

    When you have dug that hole, and most importantly recorded everything EXACTLY as you find it (a digital camera and something to use for 'scale' will come in handy), I want you to fill the hole back in (remembering that the last shovel full out, becomes the first shovel full to go back in).

    By doing the above, I reckon you will answer heaps of questions that you have about soil (about its colour, texture, composition, moisture content, air content, organic content, etc etc etc), and you will learn a great deal about the 4 componants that make up soil, and best of all, you will have learnt it for yourself. Don't forget to smell (and maybe even taste, if you dare) a sample from each 'horizon' as you work your way down to the bottom of the 'profile'.

    And above all, do it safely ;)

    I look forward to your findings, and don't forget, the very first 'rule' of permaculture is to 'observe and interact'.

    Cheerio, for now, M.
     
  11. pebble

    pebble Junior Member

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    Re: soil types

    Thanks Mark, that's an exciting project. Luckily I already know the paddock isn't very deep before it hits rock so I guess the hole won't be so big ;-) Will report back.

    btw, I can already see that in the second, brown, jar the water is clearing much faster after a few hours than the grey jar after a few days.
     
  12. SueinWA

    SueinWA Junior Member

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    Re: soil types

    If there is some way for you to separate the jar layers (difficult!), your sense of touch can help with the 'diagnosis'. Sand is, obviously, gritty, you can feel it when you rub it between your fingers. Silt, dried and a bit scattered on a piece of paper, is much smaller, but you can still see individual grains. Moist clay feels rather greasy and/or sticky to the touch, and when dried, it is difficult to really see individual grains without a microscope, they're that fine. And if you did look at them with a microscope, you would see that they look like flat plates, which is why clay soil is so hard when it dries -- the plates 'lock' together, and resist water penetration (which is why clay is often used for lining ponds).

    Clay particles are the final breakdown of soil, it doesn't get any finer than that. Humus is the final breakdown of organic matter. Both of these are what helps to retain nutrients in the soil, but they are also the first to blow away after plowing.

    The color of soil is determined by it's mineral content of the layer; color does not indicate whether the material is clay or not. Clay comes in a rainbow of colors.
     
  13. hozzy

    hozzy Junior Member

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    Re: soil types

    Soil types are tough to judge, and they characteristics change depending on what system you used (I know the Canadian Soil Identification guide). Soil is made up from different components, which are different sizes.

    Clay is the smallest particle size (has the greatest surface area) and is very sticky. Have some wet clay in your hands (but not too wet), you hand will get sore quickly and the clay will stick to both your fore finger and your thumb is you squeeze soil between them.

    Silt which has a bigger particle size then clay (and less surface area) is not sticky, feels soap (slippery) when wet. Most people can't feel the grain of the silt in your finger, but it is possible to feel it between your teeth (if you are so inclined).

    Sand on the other hand is pretty easy to feel between your fingers, we all know what sand feels like and it is the biggest soil particle size, doesn't bind to water the same way clay does and for that reason, sandy soils are really dry because the water just drains out of it.

    Organic matter is greasy when wet, usually black, is kind of sticky, but not really (if you have a pure black substraight, can't feel anything, it doesn't feel sticky and doesn't tire your hands, it is probably organic matter).

    All of these mix to make many different soil types, like: Loam, silty loam, sandy loam, silty clay loam, sandy clay, etc. These are not important (just know they mix together, and relative stickyness (clay), soapyness (silt) and graininess (sand) will vary depending on the composition).

    Organic matter will turn the soil darker and usually isn't very think unless you are on a bog, fen or slow flowing drainage. It is that nice top soil and try to exclude it from any test as it just adds another component which will make the tests are to use.

    I hope I haven't confused this post more then necessary (I kind of like soil). I would say just feel the soil, you know what sand feels like, try to estimate the sand content, take a guess on how sticky it is (try to find a clay vein (or buy some clay from a store) and know what 100% clay feels like), make a guess at what the clay content is. The rest is silt. Use a soil triangle, and there you have your soil content. Chances are, if it isn't super sticky and isn't super gritty/grainy, it is a loam or a silt, which should be perfect substraight for growing many things.
     
  14. pebble

    pebble Junior Member

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    Re: soil types

    Thank-you both. All good info.

    What's a soil triangle?
     
  15. hozzy

    hozzy Junior Member

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