Vegetative leaf stages are defined according to the uppermost
leaf whose leaf collar is visible. In corn, the growing point (stem
apex) is below the soil surface at emergence and also during early
vegetative growth.Damage to leaves during these stages will have
little to no effect on yield (Figure 8). The growing point and
tassel are not above ground level until the V6 stage.
During the V12 stage, the number of rows of kernels per ear is
determined. Determination of the number of kernels per row begins
during the V12 stage and continues until one week prior to silking.
Since ear size and number of ovules (kernels) are being determined,
environmental stresses at this point in plant development, including
wildlife damage, can have an impact on the number of seeds produced
and the size of ears harvested.
The V15 stage begins about 10 to 12 days before silking. Silks
begin to develop on the upper ears during the V15 stage. This is
the start of the most crucial period of corn plant development
in terms of seed yield. Pollen shed begins at the tassel stage
(VT) when the last branch of the tassel is completely visible and
the silks have not yet emerged.
The reproductive stages of development begin after VT. At this
time, resources are shifted from primarily vegetative growth to
seed growth and development. The silk stage (R1) begins once any
silks are visible. Silks will emerge and continue to elongate until
pollination in 2 to 3 days. The numbers of ovules that will be
fertilized are being determined at this stage. Ovules that are
not fertilized will not produce kernels. Thus, damage to silks
prior to fertilization will result in a loss of yield. The silks
dry out after completing their flowering function; hot, dry weather
results in darker silks. As the kernels mature, the amount of yield
loss from environmental stress lessens.
Eighteen to 22 days after silking, the milk stage (R3) begins.
The kernels are highly palatable during this period and the majority
of wildlife damage occurs during this development stage. Physiological
maturity (R6) occurs about two months after silking. Harvest occurs
after the crop partially dries in the field.
Resources
For more information about growth and
development of corn plants, see the following resources.
Purdue University Crop Management CDs
http://www.agry.purdue.edu/ext/pubs/CropMgmtCDs.html
Nielsen, R. L. 2002. Corn growth & development – what
goes on from planting to harvest? Purdue University
Cooperative Extension Service, Department of Agronomy, AGRY-97-07
(v1.1).
http://www.agry.purdue.edu/ext/pubs/AGRY-97-07_v1-1.pdf
Ritchie, S. W., J. J. Hanway, and G. O. Benson. 1997a. How
a corn plant develops, Special Report No. 48,
Iowa State University Cooperative Extension Service, Ames, Iowa.
http://maize.agron.iastate.edu/corngrows.html
