Rainfall Simulator Preparation – Gathering Soil Tray Samples to Ensure a Successful Simulation


We’re here in Winona County, northeast of
Lewiston in Norton Township, on an organic pasture. This pasture, for the
last 10 or 20 years or so, has been continuously grazed. So I think the farmer
told us that there’s a 15 acre chunk and then a 20 acre chunk. And basically it’s
open the gate up and turn the cattle out, and really not manage it much at all
besides just let them graze. Now the last year so the producer has decided that he
wants to become more into rotational grazing where he’s kind of using a
temporary fence in the front of the cattle herd and behind, and kind of moving the
cattle along, and then letting the pastures rest. So that’s why we’re
starting to see a lot more thatch and residue being left if the pastures
aren’t being grazed tight to the ground. And so the management is
shifting. But over the last couple decades what we have is more of a
continuous grazed system, so we’re on the heels of that. No matter what kind of
site you’re in you want to avoid being in wheel traffic. So you have to be
careful about choosing your route. Make sure, at least that season, you don’t see
any indication of tractors or other equipment going through, because that has
a really big impact on the infiltration rate of that sample. So these are some of
the basic tools that we use to collect the samples with, tile cutting knife,
which is having something at least somewhat sharp helps with cutting roots
and also the soil. And then we also have some cooking oil which helps lubricate
the side of the pan and helps keep it from sticking. And then we have a Sawzall
for cutting the soil and sample preparation at the end. This is
a really useful tool to have. And also I would say the most important tool
is this. Yes, because you need to cut a significant way around the
cutter in order to be able to collect a solid sample. So this is our
cutter. I think we call it the cutter and I think the
cutter is probably not an appropriate term for this because it doesn’t really
cut the soil. So what you do is, it’s more as a
template or guide to cut the soil both for size and thickness. Especially if
you’re in a place with permanent cover, you want something that has a smooth
surface, so we checked this very well beforehand. So there’s no bunch grasses
or other things because whatever the highest point on the soil is, really
affects the thickness of how much soil you get from the rest of the pan. So this
is pretty uniform. There is some grass. We’re going to make an adjustment for
this later. But usually in these permanent situations, if there is a lot
of vegetation, we’ll cut it down to approximately six inches and then mat it
down. But here I think we’re going to work with it and just cut it out like
this. So you place your pan where you want it. And then usually it’s best to
have someone with you to stand on it. Yes please. So at this point you need
something sharp, a sharp tool to cut the vegetation. So this is where the tile
knife will come in. So you want to cut and remove the extra vegetation on the
outside, and do this all the way around. And then once you have that, you can
step off and take a look to see if there’s anything before hand that you
notice, that may be a problem. Or sometimes we like to move some of the
vegetation in, so it’s a way. So it doesn’t get stuck between the template
and the soil as it’s going down, and cause it to bind. So we’ll
typically move it in a little bit and then make sure everything is
uniform again. And then carefully put the template back down where it was before.
With the knives, as with everything else you try to avoid bodily
injury. It’s good idea. So we’ll start on this side, and make sure that you go
parallel with the side you’re working on and vertical also. And try to go down
about three to four inches below the surface of the soil. And if you do not happen to have a
reciprocating saw, you’ll do it like this, with a shovel. And doing it in a
pasture or permanent cover is different in this regard, as
compared to annual crops. So for this, when there’s sod, I like to start from
the edge and just push it down a few inches, and then just one shovel width,
and working all the way across, and mainly making sure the sod is fully cut. I’m doing it this way, as opposed to just
cutting it up into little pieces, so that way, when we fill everything back
in, it will be much less disturbed. And the grass we’ll be able to take over again
without it just being a hole in the ground. We try to cause as little
disturbance to the landowners as possible. So after you got this piece cut,
you may not be able to see it very well, but this is the edge, so you just
push your shovel back down in and then push it across, and you can lift your
piece of sod out and put it to the side. And you also have to note that when
we’re going to be rotating this out and pulling it out later. You need a
place to work. Also and it’s a lot easier to work in a level spot that isn’t a
pile of soil .So you can think about the possible success or failure of each
specific sample that you’re taking. Because each one is telling the story,
whether good or bad. And if you’re trying to show a good story, and you’re seeing
signs that it’s not good, you may want to reconsider where you’re
taking the sample. So this is a good point to, at least on the sod, to make
sure that it fits on, since we’re dug all the way around. So if you wouldn’t mind
stepping off, Lance. And at this point is where the knife comes in
handy. You can see here that there’s a lot of space, that the the template is
actually standing on the sod and not going in. So this is where we pull the
top off, and use the knife, and you can see, yes, where the edges are hanging. So
you just take the knife and cut it back just a little bit so it’s not sitting on
the inside edge. And also here. And if you cut a little bit extra it’s not a big
deal because we’re going to have to seal the edges of the pan before we
run it. So this is just an easier way of cleaning everything up. It helps to have
at least a fairly sharp knife to be able to cut through the roots when you’re
in sod. Otherwise, if you have a dull knife, you may be tearing the soil apart.
So we’re kind of good point now where we can kind of probably dry fit it again,
would you say? Yes, and it should be able to fit. And usually when you have
really well structured soils with a lot of roots, they tend to be, you can’t just
jump on it to make it go down. So you have to finesse it more
often. As you see, it moved down, and I would not recommend jumping on it unless
the soil is dry, because you can compress the surface and and block any pores. So
to check to make sure that it’s going to be full, you push down
along the edge and in the corners. And if it’s like this corner, is maybe a
little high, so I’ll push on this a little bit more, and then check.
But if it’s just one corner, that maybe just a low spot in the soil also.
And overall I would say this is good, and we can make any final adjustments at the
end, to make sure things are fitting. So at this point we have everything mostly
ready. We just need to dig underneath to get the soil out. So when you’re doing
this you need to decide which direction you’re going to be rotating the
template out at the end. And we decided we’re going to be going east with this.
So we’re going to put all the other excess soil on the west side, on
the long side. As Dan’s been digging out the sample here, he’s down
in 6 – 8 – 10 inch range. But we have these fine route hairs
that are actually following that path of least resistance to get down to
maybe more moisture to different nutrients. We’re looking for worms,
different beetles, different anything that kind of gives us an indicator of
the health of the soil, so that we can best represent it when we’re putting on
display. So what I’m doing now is when we rotated it out we have to put it upside
down. So we need a place to put this handle, that when you flip it upside down
it will not push the sample out of the template. So it needs to be deep enough
that the handle will not be touching the bottom of the pit. So usually I cut a
little V-notch, just wide enough for it, and set that sample aside so you can see. That should be perfect. I like to
go at least that deep so we’re right there. This is the next point at which
you can use one of these saws, if you have one available. This is to help,
especially in sod, to help cut roots, because that’s one of the
major things to deal with in these, is to make sure the roots are cut and the soil
sample is separate before you try to rotate it. So what we’ll do is take the
saw, and at about an inch and a half down from the bottom of the template, is where
you want to have the saw blade enter. So it’ll be approximately here. So now I’m going to clean this out
from underneath, take the excess soil and put on the pile. And if you don’t have a
saw, what you’ll do is, at about the same depth, you’ll push in with the shovel at
an angle like that, to help. So and also do the same things on
the ends. And if you don’t have the saw, and once you’re done with
the shovel, you just use the knife and cut across, because the less soil you’re
rotating and moving around, the easier it is to do this. And also on this
side. So this is where you break the roots. Now
we’re ready to rotate it out. So being ready, as to which direction
you’re moving it, will help make it in a smooth and easy rotation and less likely
to lose the sample at this point. Because, if everything, up until
this point, has been okay this is probably one of the times when I’ve lost
the samples the most, so what you want to do is when you cut underneath, is to hold
it well with your hands, and also on this side. So we’re going to be rotating it
this way, and so the inside hand you don’t want to be putting your arm up
above, because when it’s halfway over it’ll be blocking the the pan. So you
want to have it more parallel with the pan like this and then gripping it
with the other hand. So somebody counts off two three. Okay one, two, three. And then you just set it up there. And it should, if
you’ve cut the notch deep enough, it should be stable on its own. I can put my
fingers underneath. And if I take the soil out, I’ve got about two inches
underneath the top of the handle. So there’s no way that this is pushing the
sample up. If you remember the spots that were low, such as this corner, you can
lightly push it down and if the sample is very wet, avoid doing this too much.
But this is your last chance to make sure the sample is is full, and will fill
the pan evenly. This is the next time where the saw will come in handy for
trimming this. So, typically what I do is, if I’m using the saw, I’ll keep it
between a quarter and a half inch above the edge of the pan and just try to cut
everything off at once. That’s where having 12-inch blade is is
quite useful. Make sure, if you’re using
the saw, that you can have the blade tip pointed slightly higher, rather than
slightly lower. You can always cut things shorter, but you can’t
cut them longer. And the reason that I’m cutting it
slightly higher is as you can see on this, when you use the saw it tends to
smear just like what tillage will do. And what we’re trying to show is what would be natively without any disruption like this. So we
after this we need to remove those smears and get everything finished off.
So with the saw it comes off really nice. So there’s one worm hole here
but typically it, especially if it’s wetter, it tends to smear it all, which
even if you have a good sample it wouldn’t really impact the kind of
infiltration. And then what I do is I just take this knife, the sharp knife, and
and cut along the edges and remove extra sample that way. Because the whole purpose of doing this
rainfall simulator is to show the natural capacity of the soil to
infiltrate water. And it’s a combination of cover and soil porosity. So if you’re
if you are destroying the soil porosity in one way or another, or if it is
altered from how you would have found it in the field, you’re actually altering
the outcome of the simulator. And you try to keep it as as least disturbed as
possible. If you are doing this in the springtime, in a conventional site where
it has recently been tilled, it can be nearly impossible to collect a sample
this way. So at that point what I do is I take some of the soil from the
surface and into a bucket and then I take it back to the office and dry and
then sieve it, so it would look like what would be considered a fine seed bed.
But typically in the conventional fields the aggregate stability is poor enough
that when water hits it it will start breaking up the aggregates, and it will
it will still work. And I’m picking at this right now to open up any pores that
I may have closed through cutting it through different pieces of
equipment. I’m just trying to break things open and open the pores to
allow them to move water. So at this point we’ve got a lot of loose soil on the
surface, which we want to still get rid of because if this is
infiltrating water, a lot of soil will be going through the bottom of the pan, and
going through the infiltration pan, which may show some strange things, so we want
to remove as much loose soil as possible at this time, so it doesn’t go through
there. So if you have an air compressor, that would be ideal, but I usually just
blow it off. And at this point, also you can see if
you haven’t done a good job at cleaning up some of these spots. Also, you can see
that they may be smeared or there are high spots, or something like that. Okay
that looks good. So at this point you just stick the pan on, not too tight,
because they tend to stick. And then if you think the sample is going to be
loose or cause problems, have two people do this. Otherwise with this one I don’t
think there’s going to be problems. And you just flip it over
like that. At this point, as a dry sample it’s fine. Just to push it down through
here because it is slightly above. And you’ll have
better success of pushing it out. But if you have a wet sample, you want to avoid
pushing down on this. So this is where it really gets tricky and you need multiple
hands because the the template tends to stick into the pan. But if the sample is
stuck into the template you don’t want to use this to push down too much. So you
need to be holding everything up above the ground,
I’d say like an inch and have someone tap. So the pan is loose.
And then you need to hold, okay do it again please.
Okay so at this point is when you push the sample out while holding this up. So
if you just push the aluminum down in. So if you have a vise grip or something to
hold the the cutter, that is a good time to use that. And now it should just
come right out, and it should be even across, which it is. There are some cracks
on the side which ideally you’ll collect this a week ahead of when you use it, and
it will shrink a little bit, and you will fill these cracks in at the end. But this
looks really similar to what’s next to it. And all of the original
structure and pores should be intact. Since we’ve done a neat job of piling
the soil and sod, we can start filling in the hole with most of the
soil reserve. I’d say maybe between 1/8 and 1/4 of it. So this is why I like
to keep the sod in the same piece, so you can take this and place them back where they came,
approximately. And with a little luck and rainfall this
should recover without too much problems for weeds or other things. and
it wouldn’t be surprising in six months you wouldn’t know that we were here,
except it’d just be a slightly lower spot. This is our third sample we just
collected. So you can see that this site was obviously our pasture site that we
just collected, and these two both came from corn fields. This one is corn on
corn, conventional tillage. And you can see that there’s buried residue coming
out. This one is a corn/soybean rotation with cover crops included and
so this is some of the residue left from the previous corn crop and a little
bit of the soybean residue. And there’s still some cereal rye residue left at
the surface. We like this location. We’re pretty high in the landscape, and so
we’re trying to stay relatively high up on the top of all the
soils that we’ve been looking at and this is a good representation. We’re away
from where we parked our vehicles, where all that heavy truck traffic might be
for harvesting and hauling manure. We think this is a location where we’re not
having excessive wheel traffic. And so we’re looking at a place where the
farmer had corn silage last year, chopped it off, and then came through
with a vertical tillage so real light tillage, and really shallow. And then
immediately drilled about a hundred pounds of triticale, so another cereal
grain, and let that come this spring and then chop that all off for haylage. And
then came back and drilled in soybeans, no-till drill soybeans in. And so that’s
a neat site because it shows a larger dairy farmer that is having corn
silage every other year or so. But he’s also incorporating cover crops in between. And so we wanted to show that and see if there’s differences in the runoff
that we might expect. This farmer’s using triticale. And so we want to show that
cover crop in our simulation demonstration when we do that in a few
days. So we’ve got the roll of soybeans here, so we’ve cut those off
flush or nearly flush. And what we’re gonna try to capture is showing some of
that that crap residue within our sample. So that’s why
we’re trying to position it. And then we’ll also, because it was corn silage
last year, we’ll probably try to have a corn stock or two in the sample. Here in
Winona County we’re in Warren Township. We have a lot of dairy influence, and so the
cover crop often is going to be used for forage, compared to if you’re more
in a cash grain situation. That cover crop will not be used for forage.
It will be used as kind of more of a plow down or just something that they
spray down and plant into. So they’re not utilizing it in the same way. So we
wanted to try to capture that because some of the people that will be in the
audience that when we do our simulation in a few days will be dairy farmers. And
so this will be something they might be considering doing on their own farm. So
we just spray a little bit of olive oil. Typically we like to collect
these samples at least a week ahead of time because it allows them to
dry down, if they’re at different moisture contents. And also if we’re only
going to be using these pans once, it allows you to flip the sample at the end,
and if it is not infiltrating, it will be completely dry. And you can tell this is quite a bit
heavier. And we still have some
really pretty large, what do you call it? macro pores. And then we’ve got
other smaller ones here. Got some soybean roots that are coming
down. I’m guessing we are below the depths of typical tillage here, yeah
because you see so many of the worm and other root channels that
have stayed open. I think we’re beyond the typical depth of tillage at this
point. And the significance of that would be because the the tillage would
destroy those pathways in those root channels. It’s actually not too bad to cut
through it. I was expecting it to be. Pretty good moisture. And one thing that
probably Dan and others will look for is when you have lateral roots.
That’s an indicator that we have roots there, maybe following compaction layers.
Instead of having roots like straight vertical. Comes out like that,
this platiness. That would be an indicator of some compaction.
Here we have a one little angle worm. I cut him in half for us. It seems to be coming out fairly well. It
seems solid all the way around. And as far as with silage, I mean they tend to
get a lot of accent loads and tend to be a lot of tillage and
disturbance, and get a lot more trips, and heavier equipment. And we are
seeing a fair amount of platiness as we’re coming through. And this
is just what you find in these situations. So I think it’ll be
representative. If you see roots like this coming out,
like a thicker tap root, it’s best to use a real sharp knife and cut it flush,
rather than if you think it may tear, because that’ll open up the
pores along there unrealistically. So this is why I’m using my my regular
knife instead. So again we’re trying to get it as
level. If you take don’t take enough then the sample sets to high
in the tray, and then it’s really not an infiltration thing. It’s just a runoff
example where more of the water is just shedding. So we want to be a
little bit sunken in. I’m going to talk about how, or Dan is,
about how this is a corn silage field last year. But this this sample really doesn’t
really represent it super well to me. I mean we have one corn stock right here,
maybe a piece here, so I might add one other one. Again we’re trying to
tell a story here. Is it unrealistic to put this in there? I don’t
think so because I think we want people to relate to what we’re showing them. And
they can see that. We might have a sign down there that says corn for
silage, followed by a cover crop, followed by no-till soybeans. And so we try to you
have our sample represent what we’re after. And that’s what’s out here on the
land. And so grabbing some residue and sprinkling some on top
I think that’s sometimes a good idea. As long as it matches fairly well with
the rest of the area that we pulled it from. Now we’re gonna just fill the hole in. Here
Dan. We are on a reestablished Prairie that was seeded, I believe it was no-
till seeded about 15 years ago, and there’s several plots out here, but
many of them have between 15 to 30 different species of prairie grasses and
forbs. And so as we look around, we’ve been able to identify many of them.
And so we’re interested to see how the water infiltrates in a prairie
setting, and that’s had 10 or 15, maybe 20 years to heal after
tillage and/or cattle. So it’s kind of a transition where this isn’t a prairie
that’s been around for super long. But we wanted to kind of see how it looks and
compares to some of our other land use management. So that’s why we picked it.
It’s kind of neat. A lot of variety. And we do like to be able to
show, if we do have a chance to be able to show, one native or similar to a native
site. So it typically ends up either being a prairie or forested site
to show the highest potential. Although with prairie it can be tricky sometimes
because they were typically put in really poor land that was really heavily
degraded. So there may not have been enough time to rehabilitate the soil. So
that’s something to be aware of when choosing sites. We want to keep a uniform
sample, that’s kind of the same level. So we picked an area that’s not and a bunch
of switchgrass or big blue but it’s kind of between the big bunches of grasses. So
that’s kind of why we chose this spot. This land has been in CRP or some sort of
program for 25 years but it’s been established in prairie for 15 years. So this is the last sample we’ve got
for our set up. So I think we’ve done a pretty good job at this site of
collecting the different management and land uses in the area, including one
that will act as a standard, which is this native prairie. So to cap it off, we
finished off with this native Prairie planting. We have some corn silage
followed by triticale and soybeans. And then we have no-till corn/soybean
rotation with cover crops. We have a conventional corn on corn. And we have a
recovering permanent pasture. This does really give a good concept of things
going on around the area. And it’s nice to have a good standard and a bad
standard and then different levels of practices that use the principles of
soil health in order to show what kind of differences these make. This
been a joint project between the USDA NRCS and Winona Soil and Water
Conservation District. And so we are putting on a rainfall simulator here in
a few days. And so we’ve been out today, Dan Nath and Lance Klessig. We’ve been able
to get together and get a bunch of soil samples put together for the simulation
here for our 80th anniversary and so we’re excited to work together and also
video on for all you. And this is the best way to do these kind of projects is
partnering between NRCS or whoever is doing it. Because
it’s not a one-man show.

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