Video summary
Corn growth and development is divided into two distinct phases: vegetative and reproductive, each marked by specific stages that guide management decisions. The vegetative phase begins with germination (VE), where the coleoptile emerges from the soil once temperatures exceed 50°F, followed by the appearance of the first round-tipped leaf at the V1 stage. As the plant progresses through V2 to V6, characterized by the sequential emergence of pointed-tipped leaves and nodal roots, farmers must actively scout for early-season insects, diseases, and weeds. By the V6 stage, often mistakenly referred to as "knee-high," the growing point reaches the soil surface, making the crop highly sensitive to nutrient deficiencies such as nitrogen, phosphorus, potassium, zinc, and sulfur, which can be identified by symptoms appearing on older or younger leaves depending on the specific nutrient.
Between stages V6 and V12, the corn plant enters a period of exponential growth where biomass increases rapidly and new leaves appear every two to three days. This phase is critical for establishing a robust root system that expands throughout the soil profile, but it also presents risks from lodging, green snap, and disease. As the plant approaches V12, the potential number of kernels per ear and their size are determined, making this period highly sensitive to heat and drought stress. Management during this time involves monitoring for abnormal ear development and applying necessary insecticides or fungicides to protect the crop as it transitions toward flowering.
The reproductive phase commences at the VT stage, known as tasseling, when the tassel emerges from the stalk and pollen shed begins, a process lasting one to two weeks that is vulnerable to hail damage. This is immediately followed by the R1 silking stage, where silks become visible outside the husks and must be pollinated within 24 hours of pollen capture; this window is extremely sensitive to heat and drought, with water demand peaking at up to 0.33 inches per day. Subsequent stages include R2 (kernel blister), R3 (milk), and R4 (dough), where grain filling intensifies and stress can lead to kernel abortion starting from the ear tip. By the R5 dent stage, moisture content drops to about 55%, marking an optimal time for harvesting silage if intended, while the final R6 physiological maturity occurs when a black layer forms at the kernel base, disconnecting it from the plant and reaching maximum dry weight.
Read the full video transcript
Welcome.
This webinar is part of a series
presented by the agronomic crops team
from Auburn University and Alabama
Cooperative Extension System. The series
is brought to you by Optima Fields,
helping producers make smarter
data-driven decisions on the farm. We're
glad you're here and hope you leave with
practical research-based knowledge you
can put to work this growing season and
beyond.
>> Hello everyone.
My name is Erice Francisco. I'm the
grain crop specialist for Auburn
University and the Alabama Cooperative
Extension System.
Today we are here to talk about corn
growth and development.
Basically we have two separate phases in
a crop.
The vegetative part and the reproductive
part. If you want to know more about how
a corn plant develops, there is a
publication available at www.aces.edu.
Uh you're going to find it and read it
as your as for your convenience. Uh and
basically we're going to go over uh
parts of this publication and just to
understand how a corn plant develops.
The first stage that we call VE is the
germination and emergence. And basically
what we're going to see is the
coleoptile pokes through the soil
surface, but no collar leaf is visible
and nodal root system begins 5 to 7
days.
Uh this is when the uh plants are or the
seedlings are starting to poke out of
the soil.
Uh basically what we have here is a very
small and
and very fragile structure. Uh the the
root system is really uh starting to
develop. Uh and the soil temperature for
these uh perfect germination and
emergence is above 50°F.
Then we move to V1, which is the first
leaf or the first leaf with collar
visible, and this is the first round tip
leaf. Uh so, most people confuse the
first leaf with the V2 stage, which is
the the first uh point tip uh leaf
visible. So, the V1 stage, we got to
count this first leaf, which is the
round tip leaf, okay?
And what we
uh should be doing at this stage, we
should scout for early season insects
and diseases and weeds. Uh we got to
check initial population for proper
emergence, and we got to be able to
irrigate if necessary uh to uh
uh allow the emergence to be even,
and the number of seeds uh to poke out
of the soil uh and get population that
we aim for.
Now, at the V2 stage, we have the second
leaf. This is going to be a leaf with
the pointed tip. Uh and at this stage,
we're going to have nodal roots emerge
underground, while the seminal roots
growth declines.
Uh what we going to do at this stage, at
the V2 stage, is a scout for early
insects again, keep uh keep an eye on
diseases and and weeds, and apply the
post-emergent herbicides if needed. And
also, irrigation could be uh
an assistance to the crop.
Uh then we progress to the V4 stage,
which is the fourth leaf with the collar
visible. Uh so, the leaves laid
alternate alternatively in succession
side by side. This is how we keep
counting the number of leaves in a corn
stalk uh starting with the the The one
with the round tip and then progressing
upwards counting them individually and
naming the stage as V2 or V3 or V4 as
as the number of leaves we have on the
stalk.
The growing point is still below the
surface
until the next stage which is the V5
and right there what we're going to do
is control the weeds to avoid
competition. This is a very important
stage
for weed competition and we're going to
keep an eye on insects and diseases and
also start looking for soil soil
nutrient nutrient availability that is
going to show symptomatology if we have
nutrient deficiencies happening.
And then up at the V6 stage which is the
sixth leaf with a collar visible
the growing point and the tassel are
already the soil surface. The stalk
begins greatly increase elongation
period and we've got to watch for visual
nutrient deficiencies at this time.
Also we continue to scout the for
insects and diseases and this is the
perfect time for do our side dress
nitrogen application.
One mistake that many people make is to
confuse the terminology V6 with knee
high which is very popular to name corn
at the V the knee high stage and
associate that with the V6 stage and the
reason I don't like this terminology is
the picture I'm showing here we have
three different hybrids of corn
at the very same stage. They are all at
V6 stage and you can see that the knee
high
is different from uh for everyone. So,
we got to be able to uh name the correct
uh phase, which is the V6 growth stage,
instead of using uh the knee high
terminology.
At this V6 stage, it's very important to
um
identify nutrient deficiencies like
nitrogen,
phosphorus,
zinc,
sulfur,
and potassium. So, these uh nutrients
may show up the nutrient deficiency of
these nutrients may show up uh at the V6
uh stage very clearly. So, let's keep an
eye on the uh the nutrient status of our
plant
uh starting with the symptomatology. So,
it's very um
easy to identify nitrogen, phosphorus,
potassium. They basically occur on the
uh older leaves, while zinc and sulfur
occur on the uh younger leaves.
Now, from V6 to V10, which is the sixth
to 10th leaf
uh leaf, we have uh just a development,
the progress of the biomass uh of the
plant, and this is going to be a
exponential growth. The plant is going
to grow very fast
uh and is going to show uh leaf a new
leaf every two to three days.
And the root system is growing very fast
and expanding uh all over the profile.
Um and
the plant is going to grow very fast in
these uh in between these uh growing
stages.
Then, we reach the V12, uh which is the
12th leaf stage. Uh the leaves continue
to develop and the final number of
leaves
can be up to 20 20 leaves total.
Uh
right here, the potential number of
kernels per year and the year size are
determined. Uh
there's a very high sensitivity to heat
and drought stress at at this moment.
And what we need to do is to scout for
root lodging issues, to green snap, uh
and diseases.
So, abnormal corn ears can occur from
this time on to flowering, and we need
to spray insecticide or fungicide if
necessary and also irrigate.
Then, we move to another phase of the
crop development, which is the
reproductive phase. Uh and we we we
reach reach VT, which is tasseling.
So, at this stage, what we're going to
see is the tassel
coming out of the stalk. Uh
and the last branch of the tassel is
visible at the top of the plant. That's
the VT stage.
The silks The silks are not visible at
this time.
And the pollen shed begins and will last
1 to 2 weeks. And hail events can
severely damage yield because the yield
is going to be dependent on this
structure uh to pollinate the silks.
And then the next phase will be R1,
which is silking, and we're going to
The silks are going to be visible
outside the husks.
The pollen shed typically occurs during
early or mid-morning.
And basically, the pollens are going to
be captured by the the silks, and the
fertilization will occur within 24
hours.
It's a phase where heat and drought will
affect pollination and consecutively
final yield.
Uh at this stage, the irrigation
requirement or the water requirement of
the plant can reach 0.33 in a day. So,
it's a very high water demand.
Also, we need to keep an eye on insect
that can damage silks through feeding.
Then we move to R2, which is the kernel
blister stage.
Uh so, the kernels are whitish and ship
in shape like blister.
The moisture content is very high. It's
about 85%.
The silk turn brown and dry rapidly.
And the grain filling begins. So, R2
occurs approximately 10 to 14 days after
silking or one stage.
And any severe stress can result in
aborted kernels and reduce their number
on the cob. So, it's a very sensitive uh
stage for corn.
What we should
What we should do is irrigate as needed
and this is as this is a critical point
of the development.
And then the next stage is R3, which is
the kernel milk. The kernels are mostly
yellow on the on the outside, but a
milky white fluid inside. The moisture
content is
also uh high, about 80%.
And the R3 stage
happens approximately
18 to 20 days after silking.
Also, we need to keep an eye on
irrigation. The water demand is high and
the stress may still damage final yield
through abortion of the kernels. It's
starting from the tip of the ear.
And then the next stage is the kernel
dough or what we name
R4.
Uh the kernels are filled with starch.
The beginning of the dent on the top,
the moisture content is about 70%
and the R4 stage will occur
approximately 24 to 20 days after
silking.
Stress may still damage final yield and
the impact of
a frost on grain grain quality can be
severe at this stage.
Gladly in Alabama, we plant corn very
early and so we don't need to
be concerned about frost
at this stage.
And then we reach R5, which is the
kernel dent.
Almost all kernel crowns are denting in
a distinct horizontal line, which is the
milk line as we can see in the picture,
is seen between the yellow starchy and
white milky areas.
So, the moisture content is about 55%.
And R5 occurs approximately 35 to 42
days after silking.
This is the moment to cut your crop for
silage if
if you're going to
produce silage, this is the moment to
cut
your crop at the 50%
milking
silk.
And stress may still damage final yield.
Then we reach the last growth stage,
which is R6, the physiological maturity.
The starch line is at the
kernel tip and the black layer is a
black layer is formed at the base of the
mature kernels.
This
is a clear indication that there is
disconnection between the kernel and the
cob. So, the kernel is no longer
receiving carbohydrates or any uh
photo assimilates from from the plant
is basically done and the dry weight
reaches its maximum moisture content is
about 35% that's going to happen between
55 to 65 days after silking.
Severe stress after or six no longer
affects yield unless the integrity of
the stalk is compromised
like diseases insects or strong winds.
The harvest can proceed after this point
but grain is still wet for safe storage.
So basically we're going to wait until
the kernel dries
down to less than 20% if there is no
dryer
structure available.
With that we conclude this presentation
and if there is any questions or
concerns you may
get in contact with us. My email my
phone number is there. And I appreciate
you watching this webinar.
>> That's all for today's session. Thank
you for joining us and a special thank
you to Optima Fields for organizing and
producing the webinar series.
For more resources from Auburn
University and the Alabama Cooperative
Extension Agronomic Crops team, please
visit our website at aces.edu
or reach out to your local extension
office. We look forward to you joining
us again next time.