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Grain
Fill Period in Corn
Compliments of
Agronomy Services Department
Understanding the development of the corn plant is
instrumental in diagnosing and treating field problems from year to year.
This article is an introduction to the grain fill stage of corn growth and
development.
At growth stage V3 ears are initiated, at V6 the number
of rows of kernels is determined and at V12 the length of the ear is
determined. Each is important for the final yield outcome. After V12, the
yield potential of the crop can only be determined by how large the
kernels get. Grain fill is a critical period for stresses that might
affect the final outcome. Tip kernels are the most sensitive because they
are the youngest and the furthest down the line from incoming material
produced by photosynthesis. Therefore, anything that interferes with
photosynthesis during grain fill can cause kernels to abort. This would
include nutrient deficiencies, loss of leaf material because of leaf
disease, cool and cloudy weather, etc.
The blister stage
occurs about 10 to 14 days after silking. The silks have turned brown and
blisters begin to form on the cob. In these tiny embryonic blisters, the
radicle root, coleoptile and first leaf of the plant have formed.
In the milk stage
the kernels have taken on a mostly yellowish color and are full of milky
fluid. Starches are accumulating rapidly. The endosperm is now fully
developed. It is now about 18 to 24 days after silking. Stress at this or
the earlier blister stage can be particularly damaging.
At 28 days or thereabouts corn enters the dough
stage. The moisture content at this stage is about 70%. The
consistency of the kernel is changing to a firmer form. One half of the
total dry weight has been deposited in the kernels. The cob has now
developed a reddish color. Stress is beginning to become less of a factor,
however, sever stress can still reduce yield potential.
At the dent stage,
all kernels have "dent" in the crown. 35 to 45 days have passed
since silking. The milk line or the boundary between the more dense starch
and the still liquid portion will move down toward the tip over the next
three weeks. The last or 5th leaf has formed in the embryo.
Moisture has dropped to 50-55%
At last, about 55 to 65 days after silking,
dry matter accumulation has reached it�s maximum. The milk line has
disappeared and a black layer has formed at the tips of the kernels. The
kernels are now physiologically mature and
are out of danger from frost. The average moisture is between 30 and 35%.
Harvest can begin at anytime, however, producers will want to take
advantage of field drying to reduce drying and harvesting losses.
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