A3O-Uncaster Fanning, Saturday, July 9,1983
DEKALB, 111. - Corn and
sorghum plants go through four
distinct phases as they complete
their life cycle. A relatively short
seed germination and seedling
emergence phase is followed by a
longer vegetative growth stage. A
short reproductive phase is next
and, finally, a period of grain fill
and maturation occurs. While the
plants may remain alive after
grain has matured, they are
essentially non-productive prior to
a killing frost.
During' the vegetative stage,
plants are building a grain
production factory consisting of a
full-grown plant with 12 to 18 or 20
full-sized leaves. Com plants will
initiate a tassel plus one or more
ears and the potential kernels that
may later develop. Sorghum will
have a fully formed head with
3 Promoted
Lancaster Co.
Extension
LANCASTER Extension
director Jay Irwin announced
Thursday the promotion of three
staff members of the Lancaster
County Extension Service of the
Penn State University.
Those promoted were: Arnold G.
Lueck, from associate extension
agent to extension agent; Jan
Mane Allen, from assistant ex
tension agent to associate ex
tension agent; and Michelle A.
Rodgers, from assistant extension
agent to associate extension agent.
Lueck has been with the county
extension service since 1961. A
recognized area horticulturalist,
Lueck has written over 1,000 ad
vice columns and is responsible for
providing information on hor
ticulture and agronomy to
homeowners and farmers.
Mrs. Allen joined the county
extension staff in 1977 as a
nutrition assistant and has had an
active role in informing school age
children about nutrition. She
helped design an eight-week
education program implemented
through summer playgrounds and
youth agencies such as 4-H.
Mrs. Rodgers, a home
economist, joined the staff in 1980,
and has provided informal
education in the area of family
relations. She coordinated the
county fashion show and produced
a number of local, county and state
competitors.
Irwin said all three promotions
were deserving, and he is pleased
to see that Penn State personnel
agreed.
Four phases affect yield of
numerous potential kernel sites.
Most sorghum plants have a
tendency to tiller so each may have
more than one stalk that will
produce a head.
The reproductive stage of plant
growth is extremely important to
grain-producing crops because it is
the stage when pollination success
determines how many kernels a plant
will attempt to fill With both
com and sorghum plants, the
vegetative stage ends and the
reproductive phase begins bet
ween 50 to 80 days after
emergence, depending primarily
on the maturity rating of the
hybrid and the growing conditions -
especially temperature.
It takes kernels, and lots of
them, to produce yield. Everything
that is done to help plants get the
At
greatest number of kernels started
and matured will result in higher
yield. That’s why proper nutrition,
moisture and pest control are so
important to young, growing
plants.
With corn, tassel appearance
signals an end to vegetative
growth and the beginning of
reproduction. A tassehng corn
plant actually has several ear
shoots on each stalk. We usually
find six in our examinations.
Normally the topmost ear shoot
will dominate and develop. The one
below it may develop later, if
growing conditions are favorable.
The rest of the ear shoots, further
down the stalk, usually fail.
Sorghum indicates onset of the
reproductive phase by forcing the
head upward and free of the en
closing flag leaf. It may take a day
or two (depending in part on
temperature) for the first
yeilow/orange anthers (pollen
sacs) to appear near the up-
corn, sorghum
permost tip of the head. The
blooming process may take
several days, moving downward to
the base of the head. Sorghum
flowers are “complete,” each
having both male and female
functions. Each flower, or floret,
will become a kernel, if pollination
is successful.
The success of pollination
depends a great deal on weather,
timing, insects and the hybrid.
Usually, there is a great excess of
pollen produced and released. If
weather is very hot and dry, pollen
may be killed before it is effective.
With com, poor pollination may
result if the tassel sheds pollen, but
stress conditions slow or prevent
development of ear shoots so that
there are few receptive silks when
the pollen is flying. Stress tolerant
hybrids are least affected and are
characterized as being able to
pollinate successfully even if
growing conditions are less than
perfect.
The miximum number of kernels
that will develop is determined by
the success of pollination. Later
growing conditions determine how
many of these will survive to
mature and how heavy each kernel
will be. What you haul from the
field in the way of final yield is set
by the number of mature kernels
and the weight of each.
Heathy, vigorous plants plus
favorable moisture and tem
peratures at pollination time go a
long way toward determining final
yield. Improved conditions after
pollination can’t completely make
up for potential yield reduction due
to poor seed set. One of the best
ways to reduce risk of poor
pollination is to plant hybrids of
two or three different maturities so
that an entire crop will not be in a
vulnerable stage at any given
tune. Pealers representing full
line seed companies can recom
mend top-performing hybrids in a
wide range of maturities.