Hi, I'm Trent Roberts,
Soil Fertility Specialist with the
University of Arkansas System Division of Agriculture.
And today, for my virtual corn field day stop,
I'm going to be discussing fertilization
practices in corn.
There are three main things that I would like to cover
today that I think are
essential for a well-balanced and profitable corn
production system in Arkansas.
As we know, corn is becoming an increasingly important
component of our crop rotations across the state.
And what that means is that as it becomes increasing
in acreage, we need to make sure that we are fertilizing
it as appropriately as we can.
Three of the things we want to focus on associated with
proper fertilization of corn has to start with number one,
and that is soil testing.
So, soil testing is a vital component of
any fertilization program.
And so what we really want to do is start out with a
good, solid foundation that involves routine soil analysis
focused on those nutrients that we can
categorize using our soil test and then use those soil
tests to guide fertilization practices.
The three nutrients that we're gonna be most focused
on when we utilize those soil tests are going to be
phosphorus, potassium, and zinc.
Those are the three that we have correlation and
calibration data to support fertilizer rates based on
soil test values.
And so, like I mentioned before,
getting off to a good start with a sound quality soil
testing program is going to be essential for profitable
corn production.
The next thing that I want to talk about is some of
the work that we've been doing,
particularly with nitrogen management, both midseason
as well as late reproductive growth stages.
We've been collaborating with Larry Purcell,
looking at drone imagery as a way to predict potential
nitrogen deficiencies around that midseason,
which we would typically call like a V10 or later growth
stage all the way up into our early R1 to R2
growth stages.
So the component that I deal specifically with is going
to be the use of tissue tests
or leaf nitrogen tests to identify possible nitrogen
deficiencies in corn production.
And so one thing that is very important about utilizing
these tissue tests is making sure that we sample
the correct portion of the corn plant and we get the
proper corn parts to analyze for tissue analysis.
So, when we look at this particular corn plant,
it's obvious that it's well into the reproductive
growth stages.
But, for our particular test,
you can really start taking samples anytime after V10.
Our particular interpretation is good from V10
all the way through the late reproductive growth stages.
When you're in that vegetative growth,
staging, timing, what we're really going to look for is the
uppermost collared leaf.
So, anytime from V10 through about VT,
what we're gonna want you to sample is just the
uppermost collared leaf on the corn plant.
And that's very important because that particular corn
leaf is the one that
we've utilized to correlate and calibrate this particular
tissue nitrogen test.
What you'll find is that nitrogen concentration is going to
vary greatly across the corn plant.
And so making sure that you sample the correct leaf to
use our interpretive tissue analysis is very important.
Once we get to that tasseling growth stage or VT,
you can usually identify the ear leaf at that point.
And so once you can identify the ear leaf,
we want you to sample that particular leaf
from that point going forward.
And so if you look here, we're calling the ear leaf,
this leaf that is immediately subtending the ear on the corn plant.
So just to recap, late vegetative growth stages,
we want you to sample the uppermost collared leaf.
And for VT through reproductive growth stages,
we want you to identify that ear leaf and then sample
this leaf that's immediately subtending that ear.
Now, when you do sample that leaf, we essentially want
you to just break it off here at that collar.
And we only want you to submit this leaf blade.
That leaf blade is what will be dried and ground
for analysis.
So, when we start to talk about interpretation of these
results, what we've found is that 3% nitrogen
is kind of the magic number.
And so anytime from V10 through R2 our goal with
our nitrogen fertilization program is to try and keep that
tissue nitrogen concentration in either that upper,
most collared leaf or the ear leaf above 3% nitrogen.
And what our research has found is that when we can
keep it above that 3% nitrogen range,
we can ensure that you're maximizing yield as it relates
to nitrogen fertilization in corn.
The last thing I want to talk to you about is zinc
management in corn.
And so whether or not we're talking about corn or any of
our cereal crops, zinc management can become very
important for maximizing yield and profitability.
Zinc is most often going to be limiting on our high pH
soils and soils that have low soil test zinc.
One thing that we really want to encourage producers is
to consider is looking at ways to build soil,
test zinc over time.
So, in most of our production systems where we have
low soil test zinc and we have high pH,
our recommendation is going to be to apply 10 pounds
of actual zinc per acre.
This can be a very costly practice and a lot of producers
are a little hesitant to do that.
But the one thing that we want to promote is this idea
that if you are able to apply that 10 pounds
of actual zinc per acre,
what that does is it helps to build your soil test
zinc level over time.
And eventually, once you build that soil test zinc level,
you don't have to keep including zinc in your
fertilization program.
So although it might be kind of expensive upfront and it
may take two or three years using that recommendation
of 10 pounds of actual zinc per acre,
eventually, we're going to get to a soil test level where
we no longer have to apply that particular nutrient.
And so really, when you compare that 10 pounds of
actual zinc per acre to some of the alternatives,
such as foliar zinc in season,
they tend to cost roughly the same amount in terms of
the cost of the product and the cost of the application.
And so the difference there is when we do the 10
pounds of actual zinc per acre pre-plant,
that's going to help us build soil test zinc.
Whereas when we're doing the foliar application in
season, yes, that does correct and prevent deficiencies.
But, it does nothing to help build or increase our
soil test zinc over time.
So, what we really want producers to start considering
are ways that they can implement,
you know, zinc sulfate pre-plant into their production
systems to help build that soil test zinc over time with
the goal of eventually getting it to a level where we
no longer have to apply zinc to those production
systems to maximize yield.
So once again,
three things I want you to remember about
corn production as far as it relates to fertilization
or soil fertility.
We want to start off with a good sound soil
testing program, and we can use soil testing to really
guide our phosphorus, potassium, and zinc needs and corn.
We've got a lot of tools for nitrogen
management in corn.
So using our ear leaf tissue test is a great way to
determine whether or not you need additional nitrogen
to maximize your corn grain yield.
Along those same lines, we're finalizing some work
where we can use drone imagery to help predict that
tissue nitrogen concentration as an alternative
to the actual tissue test.
And then lastly, zinc management is very important
for our corn crops.
Anything we can do to build soil test zinc is going to be
like putting money in the bank that we can rely on later.
I'd like to thank the Arkansas Corn and Grain Sorghum
Promotion Board for their support of all of our research
and the Arkansas farmers
for their support of our research.
And if you have any questions, always feel free to ask.
Thanks.