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What we're going to do today is talk about soil origins and the formation of soils.
Unconsolidated material which sits on the surface of
the earth is actually impacted by five soil forming factors,
parent material, time, climate, topography,
and native vegetation or biotic factors.
So what we're going to do is focus in on just parent materials and show
you the different parent material types that we have here in the state of Indiana.
So the first monolith that we have here
Is a monolith with shale down here at the very bottom and
this soil has actually developed from that shaley type of parent material.
So this material is actually referred to as residuum, a residual parent material.
One percent of our soils worldwide are considered to be organic soils.
If you're up in northern Indiana, maybe in Michigan or in Wisconsin,
what you'll find is that you'll find pockets of organic soils.
In this particular soil,
it's an organic soil because it has greater than 30% organic matter.
So anything with greater than 30% organic matter's considered an organic soil.
So the highest organic matter content you usually find in the mineral soil
is somewhere between 5 and 6% organic matter or 7% organic matter.
The next type of parent material that we have here in the state of Indiana is
called aeolian sand.
Now, remember in our first lessons we talked about the horizons in the soil.
We talked about the A horizon, the E horizon, the alluvial horizon,
the B horizon where everything washes into the B horizon, and
the C horizon which is the parent material.
Well, in this particular case, you got the A horizon right here at the very top,
and the rest of this is C horizon material, or parent material.
And so what's happened, is that wind has blown dune sand along, and
so what you get are the aeolian deposits of sand.
This is called an alluvial soil.
A very common feature that we find here in Indiana,
along major rivers like the Wabash river, the Tippecanoe river, the White river.
And here's a black layer in this profile here,
and in that black layer what's happened is that the plants have developed,
flood came along, this water is sitting on top of those plants.
The plants die, all right, and contribute so this black zone to the soil.
And then what happens is that you get reestablishment of plants again,
the plants grow, and then you get another flood the next year.
So these soils, here, these alluvial soils,
this is where you're gonna find the youngest soils in the state of Indiana,
are found along the flood plains, all right?
The next soil profile is unique as well.
It is the lacustrine parent material.
In the lacustrine parent material, you get these bands that are kind of going across
here, and down at the bottom, down in the C horizon, the parent material horizon.
And in those bands are layers of silts and clays.
When this huge lake that used to cover part of the Fort Wayne
area evaporated, and when it evaporated, lots of silts and clays settled out.
And so what's unique about this particular soil, especially if you're a farmer
in the eastern part of the state, in the Fort Wayne area,
it's very difficult to pull a tillage implement through something like this.
This can can be a productive soil but at the same time,
is gonna take a lot of energy,
more energy to actually pull a tillage implement through a soil like this.
Now the two most common types of parent material that we have
in the mid west are glacial till and glacial outwash.
Glacial till is actually consists of a compact parent material.
So the rocks are very sharp, they're all mixed together with sand and
clay and silt, everything is mixed together.
That is glacial till.
This soil here the parent material is glacial outwash, and
glacial outwash actually the rocks are rounded, they're smooth.
This period of time when the glacier started to melt,
and what happened was there's this huge volume of water flowing down the river.
And what would happen it would pick up some of these rocks and
it would roll around in the water and actually smooth off their surfaces.
And so you get these very smooth rocks occurring in glacial outwash.
Also it's stratified.
The drainage is excellent, all right?
So think about it.
You've got these big pieces of rock down here.
Water just moves smoothly, quickly through soils like this.
So the final comment that I wanna make about soil formation is that glaciers have
had a tremendous impact on soils here in the state of Indiana.
So we've actually had three glacial periods.
The Kansan, which was millions of years ago, the Illinoian
which was 200,000 years ago and most recently the Wisconsin glacier,
which has essentially moved out of the state of Indiana, 15 to 20,000 years ago.
So the soils in the northern part are actually from about Seymour,
Indiana, which is a little south of Indianapolis northward,
those soils were developed in Wisconsin glacial material.
The soils south of Seymour, Indiana, and sort of wraps around the sides of Indiana,
those soils were actually developed in Illinoian and in Kansan glacial material.
What's interesting about the state of Indiana
is that the south central part of the state was not glaciated.
And so that's why the Bloomington area is so hilly.
The glaciers had a tremendous impact on soil formation here,
in the State of Indiana.
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