Field Corn, Early Growth Stages Defined

Field Corn, Early Growth Stages Defined


Hello, my name is Chris Boerboom, and with
this short video clip, what I want to do is talk about growth staging corn, especially
how it relates to herbicides, herbicide applications, and ultimately the crop safety of the corn. So the area that we’re in here has just
been seeded about a week ago, and it has just emerged. What I’d like to point out on the small
corn is first, how we’re going to stage corn, we talk about the V stages of corn,
and I’d like to point those out in this corn seedling. So, as the corn seedling emerges, there is
the cotyledon, which really doesn’t emerge much out of the soil, so this is actually
the seed. The first leaf that we’re looking at here
on the corn plant is actually a true leaf, so we want to count this leaf. The thing that we’ll notice about the first
leaf is that it has a very rounded leaf tip, all the other leaves after that are going
to have a pointed leaf tip. And, with this corn, this leaf has emerged
just far enough that we can see the collar on the seedling, and the collar is this region
right where the leaf blade reaches the sheaf of the leaf, which wraps around the stem. So, this seedling is a V1 or one collar corn
seedling, and this second leaf that is emerging, we’re not going to count that yet, until
the collar for that leaf emerges. Next, we’ll go to a slightly larger corn
field and we’ll look at V2 corn in that field. Okay, so now we’ll look at corn that is
a little bigger so that we can look at the leaf collar a little bit easier. On this corn, we’re looking at some corn
seedlings that are at the V3 stage. You can see our first leaf here, we count
this leaf here, it has a rounded leaf tip so we know it’s the first leaf, and then
we have the collar where the leaf blade joins to the sheaf of the plant, and that area there
is the junction, is called the collar. So our first leaf, the first collar, and that
would be corn seedling in the V1 stage, but as we go up the seedling here, our second
leaf, we’ll notice it has a pointed leaf tip, and then we can see the collar where
the leaf blade shows the sheaf here, so this is the second collar on this seedling, the
third leaf, and the third collar right here. So, this seedling, and these seedlings in
the field here would be considered at the V3 stage. The fourth leaf here, we can certainly see
it coming up out of the whirl, but we’re not going to count it yet until its collar
pushes past the third collar. So even though we have the fourth leaf here
and it’s fairly large, we’re not going to count it. A lot of times you talk about crop safety
with corn herbicides, and we’re worried about the corn not getting too big, there
are a couple herbicides where the corn needs to be big enough to tolerate the herbicide. For instance, the status herbicide label or
the north star herbicide label calls for corn to be at least four inches tall before it’s
sprayed, or the two collar stage. So this corn is three collar, certainly tall
enough to be sprayed with those herbicides, and here this three collar corn is probably
seven or eight inches tall. We’re going to measure the height of the
corn based on where that leaf starts to arch over, and in this case we’re probably in
that seven inch height on the corn. So those would be the two main ways that we
stage corn, either by the number of collars which is the same as the V stage, standing
for vegetative stage, or the height of the corn. A lot of the corn herbicide labels have switched
to the V stage or the collar stage to determine crop safety. Next, we’ll move onto corn that’s a little
bit bigger and we’ll take a look at some V6 corn. Okay, I actually said we’re going to look
at some V6 corn, we’re actually going to look at some V5 corn here. In staging larger corn, it’s done the same
way as earlier on. You want to find the first leaf and the challenge
with larger corn is the first leaf might start to fall off, but in this case you can still
find the first leaf–that’s our first leaf and the collar, second collar, third collar,
fourth collar, and fifth collar on this leaf right here, the sixth leaf–the collar is
still down in the sheaf, so we’re not going to consider that as a full leaf at this time. So this corn plant, right here, right now
is V5 or five collared corn plant. With several of the herbicides, once this
sixth leaf comes out, then we’re actually reaching the maximum time when we can apply
the herbicides like accent option, etc. We can also measure the height of this corn
and we’re about at 17 inches with this. Some of the herbicide labels might say the
herbicide needs to be applied before 20 inches or through the V6 stage. So we would still be able to treat this corn
plant under those conditions. I also have a V7 corn plant here, and you
can count the collars here, the first collar, second, third, fourth, fifth, sixth, and seventh
collar. So, with some of those herbicides that say
we can treat through the V7 or V6 stage, if we treated this corn plant, we might have
the risk of causing some damage because even on this corn plant at this time, the corn
is already starting to initiate the corn ears and we might end up with pinched ears as they
develop later in the summer because of some of the stress that we put on the corn plant
at this time. Other herbicides like glyphosate for instance,
talk about the maximum growth stage of V8 when we can treat that corn. So we can still be able to treat corn at this
size and even as this next leaf pushes its collar past this one we’ll still be able
to treat this one as well. So hopefully, with a few basics of knowing
what a collar is, and being able to count collars, knowing which leaf to start with,
this first true leaf with the rounded tip, count that one, you should be able to stage
your corn and make safe herbicide applications.

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