The Biology of Soil Compaction

I would now like to formally
begin today's conference, and introduce Dr.
Holli Kuykendall. Thank you very much, Eddie. Thank you for your support
with the ATT system. This is Holli Kuykendall. I'm the webinar coordinator here
at the East National Technology Support Center for USDA NRCS. And our webinar co-coordinator
today is David Lamm. He is the team leader for
the National Soil Health and Sustainability Team. Welcome to today's
webinar presentation. I'm going to let David introduce
the topic and the speaker. But I wanted to make sure
that everyone is aware that we are offering CEUs
for today's presentation. We have CEUs for the American
Forage and Grassland Council, Certified Crop Advisors,
Conservation Planner, Society of American Foresters,
Society for Range Management, and the Wildlife Society. The ENTSC will submit
your professional CEUs for all of those
different societies, with the exception of
Conservation Planner. And we ask that all conservation
planners submit on their own for their
state-specific program.

At the end of
today's presentation, you'll return back
to the webinar portal to complete step two, which
offers a brief post-test. You'll be able to enter your
certification credentials, and you'll receive, by email,
your training certificate. I want to thank the Southern
Regional Extension Forestry Group for helping us
with the webinar portal. This is their product, and
we are partners with them in being able to
offer our conservation webinars through the
webinar portal system. They provide great support,
and we really appreciate it. So David, with that I'm going
to turn the presentation over to you. OK, thank you, Holli. And again, I want to
welcome everybody. Again, this is David Lamm. I work out of the Tech Center
here, and do most of my work around the topic of soil health. And I'm really excited
about today's topic, because it's one of those
things– had I known then what I know now, I would have
been a lot better district conservationist, having worked
in Northeast Indiana for 25 years.

Before we get started with
Jim, when I introduce him, I do want to remind folks that
it's all things soil health this week. We do have another webinar
scheduled for Thursday. And what we're going
to be talking about is using the core NRCS
conservation practices for enhancing soil health. And then we're going
to go through– I got three– you're not going
to listen to me drone on. I actually have three
state-level folks. Barry Fisher from Indiana,
Joel Moffett from Colorado, and Gordon Mikell
from South Carolina will be talking
about what they're doing at the local
level, and how they're using NRCS conservation
practices to enhance soil health on their farms that
they're working on there.

So let me move on
to today's topic, The Biology of Soil Compaction. As I mentioned, as
district conservationist, I worked next to
Ohio for 25 years and spent the last
portion of my days there figuring out how
to no-till using tillage. Paring soil to
no-till using tillage. And the whole concept of
biology and relating it to soil compaction
never entered my mind. And had I known Jim Hoorman
at the time and he'd been able to
educate me, we would have done a lot greater
things than what we are able to achieve. So with that, let
me introduce Jim. Jim is the Extension
Educator/Specialist in Putnam County for
Extension Service there. He's been an extension
educator for about 22 years. In his spare time, he's
also an assistant professor at the Ohio State University
there in Columbus. And when he has a few extra
minutes on his schedule, he is working on his Ph.D.
work in environmental science. He's trying to figure out
the benefits of cover crops and how much [INAUDIBLE]
leaching and run off, and all those [INAUDIBLE].

And besides that, Jim is
coming around the country. He does a lot of
public speaking. Very strong advocate
for soil health. So with that in
mind, Jim, I'm going to shut up and let you
take over and educate us on the biology of soil health. OK. All right. Well, we're going to talk about
the biology of soil compaction. They asked me to
put my mug up there, so that's what I looked
like about seven years ago. I probably got a few more
gray hairs since then. This is actually taken, I
believe, on Steve Groff's farm when I visited there. So let's get into it.

When we look at a
soil, an ideal soil should be composed of
these different components. About 45% of it is mineral. That's just really
ground-up rock. So you look at sand,
silt, and clay. What's the difference
between sand, silt, and clay? It's just the size. So sand is, of
course, the largest, and sand will break
down into silt, and silt breaks down into clay. When I was taking
some classes, they used to say that sand
is just a clay factory. It will eventually break down. But as you look at
this, about 5% of it should be organic matter.

That's in an ideal soil. Now that would be
in a clay soil. If you have a silty
soil, you're probably looking at– maybe 2%
is a really good number. Possibly 2 and 1/2. You might even get
it up to three, just depending on the soil. But 50% of that soil
should be pore space. And if we're saturated,
that would give us– in a foot of soil– almost
six inches of water. But generally, we assume
that it's about 50% water, so in an ideal
soil, we should be able to store about three inches
of water in that top foot.

So this gives you an idea. Now, I'd like to say
that organic matter is extremely important. It's like the brains
and your heart. It controls so many things. It's a buffer for a number
of different things. And it's really
important when we're talking about soil compaction
and soil structure. Here's some common
bulk densities. When you look at uncultivated,
undisturbed woodlots, for example, we
should have somewhere between a bulk density
of 1 to 1.2, maybe 1.3. And when we talk about bulk
density, the lower the number, the less dense it is. So what we're looking
at is– and this is all in metric units.

We've got grams per
centimeter cubed. So what we're doing
is we're looking at the weight divided
by the volume. And we're measuring the
solid portion of that. So 1 to 1.2– that's going
to give us roughly about 50% pore space. 1.3– And the question
I have to ask you is what is the highest bulk
density which you can have? The answer is 2.65. So if we're around 1.3 divided
by 2.65, that means about 50% of that is pore space,
and about 50% of that is in the solid phase. And so as we look at some of
these different bulk densities, you go to a cultivated
clay and silt loams, we can get up to 1.5, 1.7.

Cultivated sandy
loams– actually, sand is a little denser, so we'll see
it actually rise a little bit. It can be a little lower
or a little [INAUDIBLE]. It's 1.3 to 1.7. And then you continue, as
we get down to concrete, it's about 2.4. Now, this was some information
that came about– that I found, I guess– was that
root-limiting, for most soils, is about 1.6 grams
per centimeter cubed. It's root-restrictive
at about 1.8. So if you look at
some of these, when we get into this compacted
glacier till, we're above 1.9. And any time you get
above 1.8, you're definitely going to
have your roots go off at a right hand angle.

They won't be able
to penetrate that. They don't have enough force. Well, actually, we've
got some new information. And this is now by soil texture. And you can see that those
numbers apply to the sand, but when you get to silty soils,
actually the ideal bulk density should be less than 1.4 in order
to have those roots penetrated. And once we get greater
than 1.65, it's too high, and the roots won't be able
to– it will restrict the roots. And for clays, this number
may seem a little low, but it's actually 1.1 or
less is the ideal bulk density for root growth. Once we get above
1.47, the roots are going to be restricted
in how much they grow. So we're starting to see some
of these numbers come out. Here's typically what we
see when we plow the field. And we talk about the plow pan. Generally what happens–
in an undisturbed soil, the bulk density
will gradually rise.

And it will gradually
get a little bit– the number will increase. But when we have a plow pan–
you'll see here about seven, eight, nine inches– we're
reaching a bulk density of 1.9. So what typically
happens is a corn root will go down through
that a soil profile. When it hits this
compacted zone, those roots will go off
at a right-hand angle. So we're really
restricting how much water, how much nutrients a
plant can get when we do that. I've seen this demonstrated
quite well in Minnesota. We had a farm out
there that we visited. And they had very nice soils. It was very dark. A lot of organic matter. But unfortunately, they
plowed both their corn and their soybeans. And they had a very
restricted layer there about seven inches down. They were complaining that they
couldn't get more than about 135 to maybe 150 bushel
of corn in most years. And it was because of the lack
of moisture and the lack– those corn roots would go
down to that compacted layer, go off at a right-hand angle,
and when it got very dry out, the soil– that corn
could not produce.

Now it probably
had the capability of going at least
180 to 200 bushel, but because of this
compacted layer, it was restricted
in how much yield it would go– how
high it would go. And when we're looking
at soil organic matter, we like to talk about,
again, the density. And soil organic matter
has a very low density. You're looking at about six
grams per centimeter cubed. Versus if we look at, say,
the average of a typical soil might be 1.45. Again, we're looking
at that bulk density, to mass divided by the
volume, so the weight divided by the volume. Soil organic matter has a lot
less density than the soil, so it has more space
for air and water. Every pound of
soil organic matter can hold about 18 to
20 pounds of water. So we like to use a
sponge to represent what that soil organic
matter looks like. And actually we've got
a nice picture here. And this came from
Brady and Weil's. On the left you'll
see organic matter. You can see the black
spaces in there. Those are the voids where
air and water can be stored.

On the right-hand side, we've
got an electron microscope of clay particles. And look at how they stack up. They're much denser. They're much tighter together. And so, we can actually–
clay can hold some water, but it won't hold
nearly as much water as what the organic
matter holds. So just to take a look at
some of those properties, here's compacted
soil characteristics. And so the density
we typically see- it's not uncommon to see
1.6 to 1.8 on clay soils, versus, say 1.45
on a regular soil. Compacted soils have higher
density than the regular soils, so again they have less space
for air and water storage.

Dense soils act like
road or pavement. They, a lot of times, will
result in flash floods. So what happens is–
think of an accordion. And when you stretch
out that accordion, you've got a much wider area. But when you compact
it, what you're doing is you're getting rid of–
the part that we're losing is all the pore space. And as we lose pore
space we have less room for air and water to
get into the soil. So also, a common thought here,
or thing we need to recognize, is that dense soils
have much less microbial and biological life in it. Typically, the microbial
life that we'll see in these dense
soils is mainly going to be the
bacteria, because they are extremely small. The fungus, which send out
these hyphae and this net, have a much tougher time moving
through these dense soils. And typically, dense
soils– they're dense because
they've been tilled, and we've lost soil structure. And that's also detrimental
to these mycorrhiza fungus. So we'll talk a
little bit about that as we get into soil structure. So here are three soil
compaction factors.

Most of us are aware that
heavy equipment, because of their weight, will
compact the soil. But did you know that rain and
gravity also compact the soil? So if we get, for
example, say, a 30 to 35 mile per hour rain, that
has a tremendous force. And when that rain
hits the soil, it can actually
compact the soil. So let's say we used
to plow the fields. And we would kind
of fluff it up. And then once the
rains would come, and the combination
of rain and gravity would then make that
soil settle back down, and it would become
much more dense.

There's also
something– we'll show that in just a
little bit– what's going on there with
the soil structure. But is there a visual way
to measure soil compaction? Well actually, I noticed
this coming home from school when I was taking some
of my Ph.D classes. That as I was going
down the road, I noticed that wherever we
had a fence row or a woodlot, or even a pasture,
it's not uncommon now that we're actually
driving down into our fields. And there was an elevation
difference there anywhere I went out and measured it. And I had a couple
professors I brought this up, and they said, well,
that was soil erosion. I said, that's not possible. Six to nine inches
of a soil erosion would mean that we
would be in the subsoil. They said, well
it's, probably soil that blew over
onto the fence row.

I said, well, I took
the measurements on the lee side of a woods,
away from the prevailing winds. And so we were
typically seeing six to nine inches of
elevation difference. And we got to looking
through the literature, and yes, this is about how much
soil our soils have compacted. So what's happened is,
is with the tillage– and you'll see this
especially on the end rows. And if you're next to the
woods– at least in Northwest Ohio– we typically now will see
water running off of the woods onto our end rows, because we've
actually compacted our soil. Think of that–
again, think about how we can shrink that soil. We're taking all that pore space
out, and what's happening now is the water tends to
stand on our end rows around the wooded areas. And the water actually
moves out of those areas. Well, if 50% of that area–
of this six to nine inches– should have been
void space, that would equal three to four and a
half inches of additional water storage capacity, or
least air and water that we could maybe
store in that soil.

Is that significant
during a drought? And the answer is yes, it
is extremely significant. So we need to be
thinking about that. Here's a very
common chart that's been used by a lot of people. This shows the
soil organic matter and available
water-holding capacity. This is in inches of water
per one foot of soil. So if I have 1% soil organic
matter and I have sandy soil, I can store one acre-inch
per foot of soil. If I have a silt loam,
I can almost store two. So it's 1.9. Your silty clay's about 1.4. As we increase the organic
matter in these different soil textures, you'll notice I can
get up to 5% organic matter. That might be a little
difficult in a sand, but if I could
reach that I, could store about two
and a half inches of water per foot of soil.

In a silt loam, almost
four, and in the silty clay loam, almost three. Again this is per foot of soil. So, if I have a three-foot soil
profile, typically what happens is that the soil surface
will have a little bit more organic matter, and then
it will decrease as we go down. So let's say I have 1 and
1/2% I gain at the top. Say in the [INAUDIBLE],
and then [INAUDIBLE] next foot I gain about 1/2%. With every additional
1% organic matter, I'm going to be
gaining, on average, almost three
acre-inches of water. And that is tremendously
important, especially in our drier regions. But the silty loam soil, I
can almost gain two inches. So that's almost the
equivalent of three inches. It's actually about
5.7 with that 1% additional organic matter. So that's extremely important. And hopefully we can
take advantage of that by adding roots to our soil
and adding the organic matter. Soil-inherent properties. When we look at the
available water in the soil– you look at the sand– the
available water is just the difference
between field capacity and the permanent wilting point. At field capacity, our soils
are basically saturated. And you'll notice here with
the sand, there's not as much of a difference.

Where we gain the most
is with a loamy soil. A loamy soil is a mixture
of sand, silt, and clay. That is also high
in organic matter. That's where we have the
most available water. And as you look at
the clay, actually we have– at field capacity–
we have quite a bit. But those clay particles
hold on to that water. Water is a bipolar
molecule, and it has positive and
negative charges. And so that clay, having
a negative charge, holds on to that water. So there the permanent wilting
[INAUDIBLE] up tremendously. We have a little less
available water to that plant. So it is– available water
is largely an inherent soil property. So what can we do about it? Is there anything we can do? Well, there is one
thing we can do.

We can add organic matter. So as you look at
some of these soils– and this is some information
from Ohio– you'll notice when we have a drought–
we had a major dry period here in 2012– it is
related to weather. A 200 bushel of corn crop
needs approximately 22 inches of plant-available water. In Ohio, we typically
receive 19 to 23 inches of water from April
through September. However, it's not too often
that we raise 200 bushel corn. Now, this last year,
we actually did that. But we had a tremendous
amount of water– rainfall– this summer. So rain makes grain. The more rain you have– but
if you're lacking for rain, what about getting that
water from the soil profile? And the question you
have to ask yourself is, do I have the soil structure
in place so that when it rains, that water slowly
infiltrates into the soil? And then can I store it? And the way to store that is by
improving your soil structure and also increasing
your organic matter. Again, every 1% organic matter
can hold anywhere from one to two acre-inches of water.

One pound of organic matter can
hold 18 to 20 pounds of water. So you have to
think about what's going on with your
soil structure. Dynamic properties–
this infiltration. I can remember when we
had this dry period. The farm right across
from me had been tilled. He tilled it two or three times. We got an inch of
rain, and my guess is probably he absorbed no
more than maybe a quarter of an inch of it. The other
three-quarters ran off.

It happened to run on
my field. [INAUDIBLE] Thank you very much. Because I had no-till, and I
had some cover crops there, the water infiltrated. But take a look at this. Where you plow the surface,
and you have a cultivated field with a bare surface,
water infiltration rate after one hour. This is in acre-inches per hour. This is some Ohio data. It's about 0.26. Now take a look at no-till. And most people assume
that no-till's always going to be better. But once you take away
that organic matter, what we call that armor,
as Jay Fuhrer likes to say, that armor on top of the
soil, that really decreases the amount of
water infiltration. Now when we get it
up to 40% cover, we actually almost double
where we plowed it. We're up to 0.46. And if we have 80% cover, we can
actually go four times higher. So we have four times
more water infiltration where we have no-till and cover. And that's what
we're talking about. We're starting to talk about
this ecological farming. The goal is not
to till your soil. Long-term no-till. I like to call it
eternal no-till.

That would be our goal. Along with live
crops year-round. That's what we're calling
ecological farming. And the reason this
works so important is because it very closely
mimics Mother Nature. So if you think of a
woods, or a forest, or a long-term
grass that's been, maybe, in pasture, those very
closely mimic Mother Nature. We have live roots there year
round, and because of that, we'll have better
water infiltration. We should also
have higher storage because that residue prevents
the soil from crusting.

As we get the better
infiltration, then, and we add organic
matter to that soil, we should be able to
store a lot more water. Let's take a look at
some common practices that have a negative
impact on soil health. Here's a soil that has
very little structure. A common practice–
in northwest Ohio anyway– is we will
do rotational tillage. We will no-till it one year, and
then the following year, we'll go through and do some
light tillage on that. And when you do the
tillage, what you do is you add oxygen to
the soil, and by adding that oxygen to the soil, you
burn up the organic matter. And so what we'll see
is that the water, then, because we have
poor soil structure, the water will pond
on the soil surface. And the other problem
is on the right. Once that water starts to
pound, it starts to gain speed, and pretty soon we start
to lose a lot of nutrients that are flowing off that soil.

Here's a field– a
long-term no-till versus a rotational tillage. These fields were just less
than a quarter of a mile apart. Same rainfall event on May 15. We got 3/4 of an inch of rain. And you'll notice on the
left-hand side, where we have long-term no-till
and strip-till corn. We have a little
better soil structure. The water was able
to be absorbed. Just 3/4 of an inch of rain,
and look how much ponding we have on this field on
the right-hand side. And at this time, I might
talk just a little bit about– think about these soils.

These are clay soils. These are typically [INAUDIBLE]. And so if you can
imagine– I like to do this demonstration
with bricks and sponges and we'll try to do this. Now, you have to imagine that
you have a brick in one hand and a sponge in the other. Both are about the same size. So which one's denser? Well, we all know that
the brick is denser. And if I were to stick
them both in water, which one would hold more water? You know, it's interesting–
the brick will actually absorb water, but the sponge
will absorb tremendously more water because it has a
more porous soil structure. So let's think about
how we made that brick. We took subsoil, which is clay. And we put it in the furnace. We burned off the
organic matter. And we dried it. Now my question to you
is, what do farmers do when they till their soil? They turn over the soil. They bring the clay
to the surface.

They let the sun dry it–
burn off the organic matter. And guess what? So what do we call a brick
laying on top of the soil? We call it a clod. You've probably all seen
farmers that have done this. They will get their
fields extremely fine. They'll work it a
number of times. When we get a heavy
rainfall, what happens? It will crust, and it'll
get just like a brick. So let's think [INAUDIBLE]. The clay has a negative charge. And if I have two bricks,
and I put them side by side, since the clay has a
negative charge, if I add a positive ion,
like calcium, magnesium, or potassium, those
two bricks are going to set up
like a brick wall.

We call these individual soil
particles microaggregates. And a little bit, we'll
talk about macroaggregates, and we'll explain
what's going on there. Here's some data,
and I'll show you a field that we have in
northeast Ohio, where we had a
conventionally-tilled field. And you'll notice
the water coming off of that is very dark. It has a brown color. It's taking a lot of
nutrients with it. On the right-hand side,
we have a no-till field. And you'll see the clear runoff
coming from this no-till field.

This is where they put
on an excessive amount of a simulated
rainfall to show what the difference in the color. Actually we've done this
experiment for the last 30 years in northeast Ohio. Where we had this
conventionally-tilled field, we had a total of over
1,500 inches of runoff. How much runoff do
you think we had where we established a
no-till field 30 years ago? We had a total–
over that 30 years– of seven inches of runoff. A tremendous difference
in the amount of runoff coming off the field. And something that we could
do to actually increase this no-till field
would be if we were to add a cover crop to
it, and very closely mimic Mother Nature. We could actually add
a tremendous amount more of organic
matter to that field. And we could store
a lot of the water that we would apply
to that no-till. Generally, with no
till fields– I'll show you a slide
in a little bit– they have very big macropores. The water can get into
the soil very quickly. But the key part is
that we're missing that extra organic
matter in order to store that water long term.

So I'll demonstrate
that in a little bit. Saving nutrients in the soil is
related to the speed of water. If I double the speed of
water, how many more nutrients can be lost? And as you look at this
slide, it's exponential. It goes from 2 to the 6th power. So if I go from 1 mile per
hour to 2 miles per hour, I actually increase
the amount of nutrients that can be lost, because of
the speed and energy that's stored in that water. I can lose 64 times
more nutrients. If I go from 1 to
4, I'm up to 128. From 1 to 8, 256. If I go in some of
our road ditches, we actually have water
that's running somewhere between 20 and 30
miles per hour.

I could be losing almost
1,000 times more nutrients with that water. So our goal now is to use
no-till with the cover crops in order to slow that
water down, increase that infiltration
rate, get the water to move down through the
soil, take away its energy, and as it slows
down, it will start to drop any nutrients
that are there. Plus, If we have live roots
there, my question to you is, what do live roots absorb? They absorb soluble
nutrients like nitrogen and soluble phosphorus–
soluble reactive phosphorus.

So by having those
live roots there, we increase organic
matter content, we slow that water down, and
we have the opportunity, then, to absorb a lot of
those nutrients. This is a slide that I produced. When we're seeing what
we're seeing here in Ohio, we're starting to
see the flashiness. We all know what
a flash flood is. We're saying that the same
thing in the northwest Ohio, because we have such
poor soil structure on a lot of our acreage. When it rains, the
water washes off the surface that's very
saturated in nutrients. And typically, what
happens– it gets into our ditches and our
streams very quickly.

You'll see this dirty water. And so what happens is the
water goes up very quickly, and then it drops very quickly. And where we have this
ecological farming, where you have woodland,
or pasture, or you have something living
and growing year round, typically what happens is
the road ditch or the stream will slowly start to come up. The water will be much clearer. It'll stay at that level
for a longer period of time. [INAUDIBLE] slowly drop. And we can actually show
that on a hydrograph. So on the right-hand side, we
have this conventional farming. And actually the area that
is in the hatched area is the same under both of these. So what happens is, under a
conventional farming system, the higher this hydrograph,
the more flooding occurs. So most of this water
will leave, say, in about two to three days. Where over here, where we
have the ecological farming, the no-till and the
cover crops, we'll actually have the
same volume of water, but it takes several
days for that water– the hydrograph isn't
it nearly as high.

So we have a lot less flooding. That soil can actually
absorb that water. And [INAUDIBLE]. One of the things– a common
misperception among our farmers is, we need to get rid of that
water as soon as possible. The answer is, that's
only partially true. We just need to get enough water
so that that plant can survive. We do not want completely
saturated roots. But if we have even just
an inch of free board there, where those roots
can get some oxygen, that plant can survive
having that water. And that water can slowly go
through that soil profile. It slowly goes through
the soil profile. We can absorb a
lot more nutrients. And it's not uncommon–
I hear this all the time. We will get a one- or two-inch
rainfall, and within a week, farmers will be coming
to me saying, you know, I wish we had another rain. I said, well, didn't you
just get one to two inches? And they said, yeah,
but it all ran off. Well, what we need
to do now is look at some of these
natural processes.

By increasing our
water infiltration, adding organic
matter to the soil, we can store a
lot of that water. Because Mother
Nature doesn't always give us the amount of water
exactly at the time we need it. Organic matter is a way
that can help us with it. It can act as a buffer in the
soil for both nutrients, water, temperature, pH, and
cation-exchange capacity. If you look at where
most of the water is taken up by these
plants, this also relates to the nutrients. It's almost exactly the same. 40% of it's going to come
within that top six inches. Another 30% will probably
come in that next six inches. We're getting at about 30%
of our water below one foot. Now if you have a
very porous soil– this would be for a clay
soil– if you have a very porous soil where
you have more sand, this triangle probably is
a little more aggressive. It may actually go down that
three to four feet in the soil.

So where we have
more pore space, the roots can get down a little
bit deeper and pull water from deeper in the soil. But this is some data that
came from a typical clay soil. What about those
hot dry summers? As we're looking at corn
production, I put this in here because this is a
really important. We just came out of a drought. At 75 degrees Fahrenheit, we
use about one acre-inch of water per week . When you add 10
degrees Fahrenheit, for every 10-degree
increase in temperature, we double our
water requirements. So at 85 degrees,
we need two inches. At 95 degrees– this is
the soil temperature– we need about four inches of
water per week for the corn. So heat and drought together
very quickly increases your yield loss because of this
detrimental effect on the soil. So I think at this
time, we were going to take some questions,
David, if you have some. I think we're about halfway
through the presentation. OK, yeah, I do have a
couple questions, Jim. Does the thickness of the
compacted layer have a role? I mean, does it have to be an
inch thick, two inches thick, before you start to
restrict root growth? Well, generally what
will happen– let's just assume it's at least an
inch deep– all roots will find planes of weakness.

So the thicker that
zone is, the more difficulty these
small roots– and what I like to say these
small roots are is, if I'm going to drill
through concrete, do I start with the big bit, or
do I start with the small one? We typically will use a very
small bit and pre-drill a hole. And so when we have
grass cover crops that have very fine
roots, they can find small planes of weaknesses. Now, the thicker that
compacted layer is, and the denser it is, the
harder it is for that root to squeeze through and try to–
And once it squeezes through, what will happen is, the next
plant– if it's a corn plant, or a soybean plant
that follows it– they follow the same
planes of weaknesses. They'll follow the same
root, and they'll gradually start to break up
that soil compaction.

They'll come together,
and then they'll expand, and they'll gradually kind
of wedge that crack open a little bit, and they'll
start to break down that compacted zone. So it does– the
deeper– if you have a very thick
compacted layer, it's going to be much tougher
for you to make improvements if it's just a shallow one. And I'll come back to something
that's occurring, now. How many people are
doing vertical tillage? Vertical tillage is where we go
maybe two to three inches deep.

We just lightly fluff that soil. Guess what? We're finding a tillage pan. It may not be quite as
dense as this hard pan that I talked about,
this plow pan, but we're finding that
these tillage pans are restricting water infiltration. And that's very, very important. Because as we restrict
that water infiltration, we're going to have more of
that water run off the surface. If that water starts
to pick up speed, it's going to take– we've
got saturated– we typically have more nutrients–
are in that zone, and as that water
picks up speed, it's going to take a lot of
this valuable nutrients with it. So it's important
how thick it is. I had another question
related to that– was the use of the penetrometer. Is there a– [INAUDIBLE] just
could explain how you might be able to use that and pick
up these compacted layers, and maybe their measurement– Typically, I think,
if I remember right, and this is going
back a little ways. We used to use a penetrometer.

Usually they'll give you inches
per square foot, I think, or what is it? Pounds per square inch. That's what it is. Pounds per square inch. I got to remember because I
haven't used a penetrometer– And I think the number that
sticks in my mind is about 250 to 300 is a very dense soil. That's kind of related
to that 1.6 and that 1.8. So you want it to
be less than 250. Once it gets over 300, then
the roots cannot penetrate it. So if you're using
a penetrometer, they are very sensitive. But they do give you
a lot of information. You can use one of those–
penetrate your soils– take a look at what the–
how that will go down through your soil profile. If you can push it down and
have very little resistance, then you have a very porous
soil and obviously that is what we're looking for. So farmers have used those. Let me ask– I've got
two quick questions. Someone wanted to suggest–
a couple people suggested a fourth method of
compaction would be grazing.

Do you have any comment on that? Yes. If you overgraze, you
can compact the soil. Typically where we mob
graze, and we only keep them on for a very short
period of time, we don't see as much compaction. But for example, if the cows are
all following each other, and– I hate to bring this
up, but let's say that you– think about
a high-heeled shoe. A woman– a 120-pound lady in
a high heel with a spike on it has a tremendous
amount of compaction. Matter of fact, the
pounds per square inch is greater than an elephant. Because you've got
all that weight just on that little spike, and
that's putting tremendous force on a small area of soil. So with the hooves,
if you've got, let's say, a 1,000
pound animal– we'll just use 1,000 pounds.

And you've got four hooves. And I don't know
what the area is. Think about how
much weight– you've got 250 pounds in
that small area. And if you have a lot
of animals doing that, you can compact soil. Now let's go back to my bricks. Remember the brick
and the sponge. The more organic matter
that you add to a soil– think about if I
had two bricks and I put a sponge in between there. I can compress those, and
if I have organic matter, it will actually
decompress those– So I can put weight on those
bricks, press them together, and that sponge has
any rigidity to it– if it's a normal
sponge– it will actually allow that soil to [INAUDIBLE]
just about like that accordion.

It will pull back apart again. So it's very important. If you over-graze a
soil, what happens? I've got a picture, I
believe, that's coming up. You'll find out that you'll
have a lot less roots. You'll have a lot
less organic matter. Typically, we get about 50%
growth above ground, 50% below ground. That's at maturity. But if you have, say,
three to four inches of grass growing
above ground, you may have 21 to 30
inches of roots. And that can help. If you've got
animals grazing that, it's just like that
brick with that sponge. They can actually– it cushions. Organic matter
cushions the blow. As long as they don't stay there
and continually go over it. If they graze that way down
and then the roots die off, pretty soon you're going to find
that that soil what will become compacted. So the key thing is don't
overgraze your pastures. I think we'll hold any more
questions 'til the end there.

So why don't you go ahead
and proceed, there, Jim. All right. So this is something that
typically farmers will see. They will see these
compacted layers where they go on these
ruts in the field. And if you have a situation
like this, how do I handle it? Well, probably the
best thing to do is, rather than– you can see
as you look across this picture, there are some rutted areas,
but it's not the whole field. Just– if you have to do
tillage to level these out, only do the tillage
right where the ruts are, and leave the rest
of the field alone.

And unfortunately, most of our
farmers, once they get started, they think that they have to
have to do the whole field. So as we're looking at
these dynamic properties– this rooting volume–
the thing that I wanted to call your attention
to– here on the right, we have a no-till field that
has a lot of roots in it. Compare that to the
structure on the left. It looks almost like
a concrete block. So it's all related to the
arrangement of the soil particles, the root development,
the water infiltration.

Some interesting facts. Compaction can reduce
your yields up to 60%. I just got some
data from Australia. Tim [INAUDIBLE] said where he
went to controlled traffic, he was able to increase his
yields anywhere from 10 to 40%. So this 60% would be
where we really severely compacted our field
year after year. The other thing
is, compaction has been shown to persist for
up to nine years in a field. Just natural
freezing and thawing will start to break up some
of those layers of compaction, but it can persist for
quite a long period of time. As we look at increasing
that root volume, we're going to now talk
about aggregation– soil aggregation– and
aggregate stability. All these promote
biological activity. They increase the
organic matter. No-till is a good way, but
no-till with a cover crop is even better. We want to prevent
that slope compaction, and in order to
prevent that, you need to stay off
soils that are wet.

Where we have controlled
traffic, or managed traffic, the first time after you till
a soil, or the first time you run across that soil,
80% of the soil compaction from that wheel traffic
is going to occur with [INAUDIBLE] first pass. So tillage is a
short-term solution. Generally it lasts
only about a year. If you want long-term
solutions, you've got to add roots to your system. And the best way to add roots is
to grow your main crop– follow that up with the cover crop. The goal is to have live
crops growing year-round, 12 months out of the year
if at all possible. Let's take a look at how
these ruts– how they form. Here's a tractor wheel. And notice with the weight, I'm
pushing down onto that soil, but there's also
soil underneath it.

So what happens is, a lot of
the soil gets moved to the side. But there's already soil there. So what typically
happens is that we'll start to form this typical hump. So this little bit of
a hump in the soil. So typically, if
we're going level, we'll have a little
bit of a hump. And then we've got
our deep rut, a hump, and then the soil
will level off.

And it's interesting. If I take a disc,
and I actually disc that– If you've ever
disked shut a rut, you'll notice that it seems
like you've lost soil. What you've actually done is
you've compressed that soil, and that loss is that
50% loss of void space. So compacted soils tend
to have less void space. Typical soils that
we have now probably have lost any where
from 25 to 35% of their void space in the soil. But let's take a
look at this root. This is an oilseed radish–
a tillage radish, I believe, in this case. Roots actually do the same
thing– they take up space. And so we've got this big root.

It pushes down, it pushes
this soil to the side, and then it physically
lifts the soil. So roots compact the soil,
but they compact the soil with a purpose. And we'll show you
what's going on here. So we've actually
taken some measurements on soil compaction. This was done on
Dave Brandt's farm, southeast of Columbus, Ohio. And here's what we found. Out in the open field, compared
to where we had the radishes, compaction decreased
by greater than 40%. So things like oilseed
radish, sorghum sudan grass, annual ryegrass, cereal rye. These are all very
good plants that can be used to decrease
soil compaction. We generally say that
most of these roots can penetrate the soil
about a foot of soil. If the soil's very compacted or
has very poor soil structure, we can gain about
a foot per year.

So that's why it takes
a little bit longer. If I'm going to
use roots, I may be able to penetrate
about a foot per year. If I have poor soil
structure all the way down– say three feet deep– it may
take me two to three years to break that soil up and to
improve that soil structure. Here's what the roots and
the fungi– the hyphae– do. You'll notice these
are clay particles, and these are the roots. They realigned these
clay particles. We call these individual
clay particles– we call them microaggregates. And these may be a
combination of– there may be a little bit
of roots in there, a little bit of organic matter.

But as we realign these, we
will compact them together. And then what will
happen is a root will give off some
root exudates. And we'll get some glomalin
from the mycorrhizal hyphae. And what we will
form is something called a macroaggregate. So if you want to see what
a microaggregate looks like, they're about the size of
a small piece of sand– maybe a piece of gravel. Just dig up some
soil in your lawn. Dig it up and kind of
shake it, and you'll see these little soil pats that
are all attached to the roots.

Those are macroaggregate. So here's a question I always
like to ask my farmers. I say, if you have a lot
of clay in your soil, wouldn't you like to have
some sand and gravel? And Mother Nature
has a way to do that. If you can grow
more roots in there, you can actually form
these macroaggregates. That will let air and water
go down through your soil. Now the interesting
thing is, these are all– these macroaggregates
have these polysaccharides and all these microbial
waste around them. They're actually insoluble. That means they're coated
with this material, and the water will
actually be shed off there. It's interesting– inside
these macroaggregates is stored a tremendous
amount of carbon. And these macroaggregates
serve two functions. If I take a macroaggregate
and take one of these pats, put it between my fingers, I can
turn it into a microaggregate.

That's what happens
when you till the soil. And we all know when we
till the soil, that's going to be like those bricks. They're going to set up
just like a brick wall, so it's going to form a crust. These macroaggregates may
only last for a couple weeks– a couple months– a very
short period of time. The microbes use the glues
and all of these wastes. And that is their food source. So they're continually
being formed and reformed in the soil, but if you
don't have live roots there, you're going to lose them
after a couple months. And that's what causes
our soils, then, to lose its soil structure. So live roots are very key to
having good soil structure. Here's the bacteria.

They're associated more
with the microaggregates. They're breaking these down. 40 to 60% of the soil
microbial biomass is associated with
these microaggregates, and that's where
the bacteria is. They're the ones–
90% of the bacteria are linked to this clay. And that's why, in very
poor-structured soils, we have a lot more
bacteria than we do fungus. If we want to
increase the fungus, we have to stop the tillage. We can't over-fertilize. Too much fertilizer and
tillage kills off the fungus. The fungus are going to
give you that glomalin. And so here's what this
macroaggregate looks like. These very small gray ones
are the microaggregates. This macroaggregate is
all these pulled together. And then it's kind of got
this– either glomalin, or these polysaccharides
coating them all together in a microbial waste. That's what helps to form
these macroaggregates. If I till the soil,
this will break open, and very quickly, the
microbial population, especially the
bacteria, will consume all these polysaccharides.

And all I'll be left
with is microaggregates. And that's why our
soil then starts to– we start to have
poor soil structure. These are these
mycorrhizal fungus. You'll notice how they
infect– this is a corn root. And look at the size of them. These are about 1/10
the size of a root hair. These mycorrhiza can actually
explore 20% of the soil. A corn root by itself can
only explore 1% of the soil. And what these mycorrhiza do is
they're like a freight train. They're bringing back
water, bringing back soluble nutrients– nitrogen,
sulfur, phosphorus– all these micronutrients
back to the corn plant. The corn plant, in exchange,
is feeding these mycorrhiza and giving them sugars
in order to survive. Where we have too much tillage–
too much phosphorus– then we tend to have less
microbial biomass in the mycorrhizal fungus. And here's a mycorrhizal fungus. Which one is it? It's actually the white ones. Sometimes they'll be
a little bit yellow. Just in a handful of
soil, we can actually have several miles of
these mycorrhizal fungus. That root hair is actually
a little bit brown.

And these mycorrhiza will
tend to be yellow or white. And when they die, or when
they start to– if one of them is broken off, what happens
is this glomalin, or glomulin, that's what surrounds
this soil particle, and that's what gives our
soils good soil structure. So this is going to help to
form those macroaggregates. So when I go and dig in a
soil that's very healthy, and the soil just
crumbles, that means it has a lot of fungus– a
lot of these macroaggregates in the soil.

Building soil is like
building a house. The architecture
is Mother Nature. We have the plants. We have the sand, silt, and
clay, which is our foundation. The roots are going to be
the frame for our house. The nails are going
to be the humus. The lag screw will
be the phosphorus. We've got braces–
that's going to be the nitrogen and the sulfur. The polysaccharide is kind
of like the insulation or the glue. And the glomalin is kind
of like the house wrap. And then we have this roof. So let's take a look at this. Here's a typical house. We start with our foundation. If you're in a room, just
look at the pore space that you have around
you– all the air. Why is that there? Because generally we tend to
have wood studs in a house.

And so that wood is going to
be attached to our foundation. If this is a brick
wall, we're going to use the phosphorus lag
screws to attach that together. Carbon, by itself, is
almost like spaghetti. It's very flexible. But when I add double
or triple bonds, and I also add some nitrogen and
sulfur to it, it has rigidity. And so those are going to act
like the places in the soil. They're going to
give our soil room. That we add more pore space. The nails are kind of that
long-term humus that's been around for 10,000 years. The glomalin is kind of
like the glues in the house wrap around the house.

And then we have our roof. Now it's very
important that you have a thick layer of organic
matter on top of your soil. So imagine if every other year,
we had a tornado come through. This tornado's called tillage. If the roof came
off of my house, what would happen to the
interior of my house? If I can't get that roof
replaced for a while, we're going to get
rain inside the house, and my house is going
to start to rot out. The wood will rot out, and
my house will collapse. What happens in the soil? It's not too much water. It's too much oxygen. Too much oxygen causes the
organic matter to be oxidized. It's burned up. It's just like if you
have a wood stove. If I open the damper, fire's
going to burn brighter, and we're going to
lose all that carbon– will go out the smokestack.

Same thing happens in soil. You put too much oxygen in
there, we're going to lose it. So it's very important that we
have a thick layer of residue on the soil surface to keep
the amount of oxygen and carbon dioxide in the soil in
the proper proportion. And so oxygen and carbon
dioxide are inversely related. Carbon dioxide is
heavier than the oxygen.

As one goes up, the
other goes down. So if I open a soil up, all
the carbon dioxide to escape. And I'm going to
have more oxygen. The microbes are
going to flourish, and they're going to eat
up all these glomalins and polysaccharides
and glycoproteins. All the glues that
I need in my soil to give me good soil structure. Here's what happens
when we break open those macroaggregates. You'll notice the
carbon dioxide being lost– the oxygen coming in. And so we end up– we
go from a macroaggregate to microaggregates. Microaggregates are the ones
that set up like a brick wall.

Those are the ones
that are going to form your clods in your soil. Wrong way, sorry about that. So what about if I have
cold no-till soils? Typically farmers will tell me
that when they start to farm, they're starting in no-till,
their soils are cold and wet. When I talk to
long-term no-tillers, they tell me their soils
are warm and moist. So what's the difference? Well, imagine this– is
you come out of the winter, and you went from a
conventional-till field, to a no-till field. Did you get rid of all
your soil compaction? Probably not. So what you've got, typically,
is you'll have zones. You'll have a lot more water. So we come out of
the winter– is we have this water stored
in the soil profile. Probably a saturated
soil profile. Water holds the heat. It also holds the cold. So it takes 10 times more
energy to warm up water than what it does air. If I have very good– if I
put in a nice cover crop, and I can break up
those compacted zones– get that water so it will
drain through that soil, I actually can induce a little
bit more oxygen into that soil.

And by doing that, I will
warm that soil quite quickly. Now, didn't I just say oxygen in
that soil might be a bad thing? Here's the thing. Remember we told you that those
macroaggregates were insoluble, and most of the carbon
is tied up in there? If we can control
this, what will happen is they will slowly
break even open. It's not like we have
the a big rush of air.

When you go through
and do tillage, you're really disrupting
those macroaggregates. You're breaking them open. But now that we're using roots,
we're a little more gentle. We're not going breaking open
those macroaggregates as much. And even though we've got a
little more oxygen in there, we're not putting all
those forces on there to break those macroaggregates. Now let's go out another
two, three years. And let's say we're
starting to get some residue on top of our soil. What color is to
residue when it's down? It turns black. And black will absorb the heat. It will help to warm your soil. Let's go out another
two, three years. Let's say now we're starting to
get a thicker layer of residue. And when you do
that, what happens in the middle of a compost pile? It actually starts to heat up. Actually, it's very difficult
to get thick layer of residue. Because most long-term
no-tillers tell us they have so much
biological activity that that residue actually
breaks down quite quickly.

It's only these
conventional farmers that are having that trouble
breaking down their residue. Are we getting close
on time, David? Yeah, Jim. I think if you're
about at a point there, we might want to to
wrap it up, unless– All right. We'll make this the last one. As you look at
your crop rotation, drilled soybeans have
a poor root system. They have a
thicker– when you're following drilled soybeans with
corn, that has a thick root system– that's part of the
reason why no-till suffers, especially that corn. If we can add a cover
crop in between there, we can actually help
that corn to break up those compacted zones.

So you've got to look at
the percentage of time you have live roots. Does no-till have
more live roots than conventional tillage? Not by itself. It's not until you
add that cover crop. What's missing in the no-till? You've got to have live roots. So this is basically
a biological problem. You've got to have
live roots in your soil to have good soil structure. All right. All right, Jim, thanks. That's a lot of
information, there, and again, I wish I had heard
this about 10 years ago.

And I would've been a lot
more successful in my career out in the field. I do have a few questions
here I want to follow up on. A question about what's
the role of earthworms? Do they mess up the compaction? Or have you got a
comment on that? Earthworms are extremely
good at helping to form macroaggregates. And so I'm glad you asked
that, because I actually have a couple pictures.

You might want to tell people
the slide set is available. A lot of the pictures– not all
of them are self-explanatory, but I'll explain two of the
pictures that we're looking at. What happens is, when
you've gotten macropores, just by themselves, sitting
in a no-till situation, with earthworms. The problem that
we're getting is, we're getting a lot of very
fast water infiltration. The water moves down through
the soil profile very quickly. It takes a lot of
soluble nutrients. And then a lot of
those nutrients may be lost out the [INAUDIBLE].

But when we add a
root, what we do is we add a root
to that profile. And that's going to
slow that water down. It acts like a biological plug. And it will move the
water– think of macropores as superhighways moving
things very quickly. Now we're going to move that
water into the micropores, and the biopores, and
where the roots are. And then the roots can
absorb that nitrogen, absorb that phosphorus,
and reprocess it. So what we've done is disrupted
some of these natural cycles in the soil.

Earthworms have been– they've
claimed that they're a problem. Actually, if you put
them with live plants, they're not an issue. It's not an issue. What about use of controlled
traffic, and precision ag, and that type of system? Have you had
experience with that? Yes. What we're seeing is, where
we use the controlled traffic. As I said, Tim–
I believe his name is Tim Robinson–
from Australia. He's been doing this for
a number of years now. And Randall Reeder at
Ohio State has some data. What were finding out is
that it is a little more compacted in that wheel track.

But then outside
of that wheel track will be down around– bulk
density in the wheel track may be 1.5 to 1.7. Just a small zone. But outside of that
wheel track, it'll be about 1.1 to 1.3 grams
per centimeter cubed. So we're getting the
exact– what we want to. We want to have that
good soil structure. And we're seeing yield
increases of anywhere from 10 to maybe as much as
40%, or theoretically it's possible to get as much
as 60% yield increase just by using that
controlled traffic.

OK, good. Two more questions, then
I'll let you go, Jim. I know you've already made
one presentation today, and this is on top of that. So we appreciate
your energy here. A question about crops. You mentioned some good crops
for residue– or not residue, but roots. We have alfalfa– would
that be considered– what are some of your–
give me your top five or six that you recommend. Well, let me just go
to that real quick. Here's some other
information that we had. This is what subsoiling does. If you're doing
conventional, you're going to get about a 3
to 10% yield increase by doing subsoiling. Without the subsoiling,
if you're no-tilling, you're actually going
to get a decrease. And so subsoiling will do
just immediate changes, whereas the cover crops
are going to be long term.

So I think I'm getting to that. Here's all the different soil
resistance to compaction. And here's the best one. Continuous no-till, controlled
traffic, cover crops. There's my slide. The best cover crops to
fight soil compaction are the sorghum sudan,
the annual rye grass, and the cereal rye. If you're going to
grow the sorghum sudan, let it grow up as a forage. Let it get about
three feet tall. Either mow it off or harvest it. The reason we do that
is because you get five to nine times more roots. That's a 500 to 900% increase. If I'm going to use
brassicas, use the radishes.

Don't use the turnips because
they're shallow-rooted. For the legumes–
whoops, sorry about that. Use the hairy vetch, then
the cowpeas, the red clover, and the winter peas. If you've got surface
compaction, use buckwheat, and for deep compaction, you
can also use the sunflowers. So those are some
of the ways you can fight your soil compaction. So I actually got done here. That slide set is available if
somebody wants to look at it. Most of those last slides are
pretty much self-explanatory OK. Well, I think I'm going
to cut it off there, Jim. And again, I
appreciate your effort. And I just thought and pondered
that usually a woods left in the northern– northeast–
or western Ohio farm was there because
it was too wet. And now you're telling me
because they're draining out of the woods into the cropland. Wouldn't our grandfathers
be embarrassed about that? It's interesting because we
are now actually driving off– when we go into
our fields, farmers are noticing that there is
an elevation difference.

They are actually driving
down into their fields. And that is due to the
poor soil structure. As much as it is–
I mean what we call soil compaction–
a lot of that is actually poor soil structure. Well, Jim, you've done
a great job of it. Got a few comments here and the
folks appreciate your effort. Very thorough and complete. And again, I want to thank
you for your effort here. And I appreciate your
time in this presentation. As far as the
participants, I want to remind everybody–
there are handouts, and the presentation
is available at the site, and if you want to get
credit for this– CEUs for whatever certification
you're going after, you'll have to go back
there, and there's very good instructions
at the site. So with that, I'm going
to call it a quit. And again, Jim, I
appreciate your effort, and I look forward to seeing
you next week out in Omaha.

Yes, we will see you there. OK. And we'll call this
quits for today. And I look forward to
Thursday's webinar. Hopefully a lot of you
could join us then too. Take care. .

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