Hello, my name is Jason Kelley.
I'm a Wheat and Feed Grains Extension Agronomist
with the University of Arkansas System
Division of Agriculture.
And today, I'm at the Lon Mann Research Station just
south of Marianna, and want to take just a couple
minutes and talk about a crop rotation study
that we have ongoing here at the station.
This is a unique project.
This is a project that we started in 2013,
and it's unique that it's funded by the Arkansas Corn and
Grain Sorghum Promotion Board,
the Arkansas Soybean Promotion Board,
and the Arkansas Wheat Promotion Board.
And really, the reason we started this project,
if you think back over the last 30 years or so,
a lot of things have changed.
You know, our crop rotation has changed.
If you just think about the soybean side of this,
30 years ago, we had a lot of wheat,
double-crop soybeans, and as we transition to today,
we typically try to plant a lot of our soybeans
as early as we can.
And that's typically in April.
And we're also planting earlier maturing soybeans
as well, so we went from a double-crop system all the
way to almost a very little wheat today to early
planted soybean system.
At the same time,
our corn acres have dramatically increased.
We went from 100,000 acres roughly 30 years ago,
all the way up to 650,000 this year.
In some years, we even had more than that.
And so, a lot of our growers are incorporating corn
into their system.
And so, this project really wanted to verify, you know,
we were making the right decisions yield-wise,
economically wise, whether taking the going to that
early planted soybean system and including corn
was the right thing to do.
This project we started in 2013 and we wanted to look
at 8 rotations, and I'm not going to hit on all the
rotations today, but the main
ones we want to concentrate on,
we've got to continuous early planted soybean.
So, in this situation, 38 inch rows, furrow irrigated,
planted in mid-April,
a group IV soybean, that's kind of our standard.
We've got some plots out here.
We've grown continuous soybeans for seven years,
it's the seventh year of this project.
We've also got corn, we've got some plots that have had
continuous corn for seven years.
But, you know, the main one we want to look at is
soybean one year, corn the next year.
So, that's kind of our standard treatment we're
evaluating. Then we've also got wheat,
double-crop soybeans.
We've got grain sorghum in here kind of in place of corn,
so we've got grain sorghum followed by soybeans.
I've got some other combinations with wheat in there.
And so today, I just want to touch on basically the
highlights of this project.
And so if we look at just the yield response and
economic response of including corn or
grain sorghum on early planted soybeans,
it's really pretty dramatic.
And so the 6 years up until this year,
early planted soybeans.
We've averaged about 54 bushels on continuous
soybeans, which is okay, but where we put corn
or grain sorghum in that mix.
So the early plant soybeans are following
corn or grain sorghum.
Our yields go up 6 to 8 bushels on average each year.
So that's pretty dramatic when you think
6 to 8 bushels at 8-10 dollars a bushel, that's quite
a bit of money that we can gain just from crop rotation.
Our corn yields, what we've seen, we've got one rotation,
where it's continuous corn planted every year,
Not necessarily a practice that we would normally do,
but we do have acres that are planted that way.
But in this situation, where we planted corn following
early April planted soybean or double-crop soybean,
those yields are always a little bit better than
our continuous corn plots.
Not a lot, I think about 7 bushel per acre better when we
follow soybeans than our continuous corn plots.
We also have incorporated wheat in these plots.
So, we've got plots where we have corn followed by
wheat and then double-crop soybeans.
And then we've also got wheat following,
so we've got wheat following corn,
grain sorghum or soybean, and our wheat yields are
always a little bit better when they're following soybeans
than corn and for sure grain sorghum.
The reason for that's really hard to say.
We're doing everything the same,
but it seems like every year the wheat yields out of
the soybean plots are always a little bit better.
Some years that following corn is pretty close to where
we were on soybeans, but when we follow
grain sorghum, there's always a little bit of a drag there
not really sure why we're putting the same amount of
nitrogen out there, but that's something we've seen in
these plots, not a lot of grain sorghum out
there this year.
But, when prices get up, that is something that more
producers may be looking at.
We're also looking at the economics of these rotations.
You know, we can talk about what impacts yield and
all that, and if the economics don't work out,
it really doesn't mean anything, right?
So, we've run the economics on all these rotations
6 years through from the very beginning all the way to
6 years, and it's really amazing to me that it's very
intuitive that if you don't have the bushels and you don't
have the good grain price, that rotation is probably not
going to be as economical as some of the others.
And so, when we look at the economics
over 6 years out of these 8 rotations,
the one that really comes up to the top is the corn,
followed by early planted soybeans, you know,
50/50 mix corn one year,
early planted soybeans the next year.
And that really comes out to be the economically
highest return rotation.
Whereas the ones with wheat or grain sorghum,
maybe we didn't get all that good of a yield one year.
If the price wasn't very good when we were doing the
economics on these — 3 dollars a bushel for grain
sorghum, that really pulled down the economics.
So we may have had good yields, but if we don't have a
good price to go along with it as well, you know,
the economic return may not be as great as what
we would like to see.
We've also been at the conclusion after harvest,
each year we take soil samples out
of every plot in this field.
And so, we've been tracking nutritional changes
over time, specifically phosphorus and potassium.
You know, in all these plots, we'd soil sample.
We follow current University of Arkansas
recommendations for fertilizer and between
phosphorus and potassium,
on all these rotations, we're really not seeing a big
change one way or another,
not increasing levels and not decreasing the levels,
regardless of what the rotation is.
The one exception is zinc.
So where we have corn out here,
we're putting 10 pounds of actual zinc per acre
in the very beginning.
And over time, those zinc levels have come up.
So when we first started this trial our zinc levels were
very low, pH about, soil pH about 7-7.2.
We needed zinc.
So now we've raised those zinc levels up enough that
the soil sample is not calling for new zinc on
corn the next year.
So one other thing that we're monitoring during the
duration of this trial is soybean cyst nematodes.
We have a lot of nematodes out here, other areas of the
state have root-knot nematodes, but we only have the
soybean cyst nematode out here.
And so when we started this trial,
we had levels that were really high in most plots and
then we imposed these rotations over 6 years.
Things have changed.
And so, we've incorporated corn or grain sorghum,
those soybean cyst nematode numbers
went down considerably.
And that's probably one of the reasons why we're seeing
the increase in soybean yields. They just cause the
reduction in nematode numbers.
One other thing that's very obvious in these
rotations is weed control.
And so, if you look out across these plots, they're clean.
Very few weeds out there.
But pigweed is our main nemesis.
And this field, prior to starting this rotation,
was used by our weed science project.
And so, we had lots of weeds out here,
specifically pigweed.
So over time, we've gradually reduced the pigweed
numbers out there.
And I hear a lot of producers say they want to grow corn
because they have a lot of options to control pigweed.
And I agree with them 100%.
We have options, a lot of options in season that we can
control pigweed,
especially if we use a two-pass program,
some herbicide applied at planting and then a
post-emergence later on.
So if we do that, we start clean.
We ought to get pretty long season control.
Now, I see a lot of fields at the end of the year get
pigweeds out there and they go to seed,
but in this situation, as soon as we harvest the corn,
we're either spraying Gramoxone to kill any pigweed
escapes or we're doing some tillage.
So when we do that,
our pigweed numbers have definitely went down.
But even with that,
the continuous soybean plots out here,
if you go through there our crew, myself,
we've chopped pig weeds out here.
There's always a lot more pigweed in those plots versus
ones that have been rotated.
So that's definitely an advantage to having some
rotation out there is weed control.
One other thing that we hear a lot about on
crop-rotation is diseases.
And, you know, we've got corn,
soybeans, wheat, grain sorghum.
And really on these small plots in this situation,
we have not seen a whole lot of differences in—
in disease pressure.
Can't say that the rotation is really helping
or hurting this there.
So in conclusion,
this trial demonstrated that we can increase soybean
yields when we incorporate corn or grain sorghum
into that rotation.
I think one of the main reasons why our soybean yields
have went up is just the fact our soybeans cyst numbers
have also been lower because of this corn
or grain sorghum crop in there.
So we can increase yields,
that doesn't necessarily mean we increase profitability
or overall economic returns.
That's a lot of times dictated by grain price.
So if we get a good grain price in combination with the
synergistic yield increase with rotation.
I think that's really what we we're looking at.
