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Soil Texture

Soil Texture


Soil texture is a very important soil property.
Soil texture is comprised of three different sized soil particles, and they are sand, silt
and clay. Sand is the largest, silt is the medium sized and clay is the smallest. This
ball represents sand. As you can see it�s kind of large and it is, in this case, it�s
a sphere, but in reality, sand particles are round shaped, but they are tend to be a little
more irregular than just a sphere. This small ball represents a silt particle. Similar shape
to the sand, however, it�s much, much smaller. This piece of paper represents a clay particle.
Now you can see, if I hold it this way, it�s fairly broad, but if I turn it this way it
is very, very thin, and that�s why we call them clay plates. OK, so clay particles are
shaped like sheets of paper and we call them plates. Now generally in a soil, you can find
sand and silt particles on their own, however, with clay particles, they tend to appear as
a stack. OK and that stack is a bunch of clay particles all piled on top of each other and
stuck together using chemical bonds of some sort or another. Now what�s interesting
about clay particles, and one of the things that gives clay particles some of its interesting
properties, is that clay will shrink and swell. And so, the clay particles can actually get
further apart, or closer together. And so, if something large gets between the clay particles,
like this ball, let�s see if I can do this, like this ball, it pushes the clay particles
a long way apart. If something small gets between the clay particles, like the silt,
like the smaller ball, the clay particles are a lot closer together. Now, what can get
between clay particles? Clay particles can have water get between them, and it can get
ions get between them, and if you have a large ion it pushes the particles apart, and if
you have small ions it pulls them together. With water, what happens is, water will get
between layers of some clays and force them apart, and then, when they get forced apart,
the volume of soil actually gets bigger and so the soil swells. As water leaves from between
clay particles, clay plates, the soil, the particles get closer together, the volume
of soil decreases and the soil shrinks, and that�s why we get cracking in the middle
of summer, is the soil shrinks because water disappears and the clay particles get closer
together. Now soil texture comprises of the different sizes of particles, but those particles
are very specific in nature. They are mineral particles. OK, so when we are talking about
soil texture, we are only talking about the minerals that are found in the soil, we are
not talking about the organic matter at all, we�re only talking about the soil minerals.
This is a jar of sand sized particles and you can see that they flow over top of each
other very, very easily. They�re almost big enough to see individual particles, even
on the screen. In real life it is very easy to see the individual particles because they
are so large. They flow across each other very, very easily, indicating that they are
pretty much round in shape. This is a jar of silt sized particles that
I�ve been, that the structures been destroyed in and you can see that the silt sized particles
themselves are, they�re very small, difficult to see, but they do flow and roll across each
other, indicating that they are round.

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