Page 22—Corn Talk, Lancaster Farming, Saturday, February 10, 1996
Post-Maturity Grain
Yield Losses In Corn
STATE COLLEGE An
article in the October 1995
Farm Journal concerning a
recent stud? on “post-maturity”
yield losses in corn has
received considerable
attention.
The article described ongo
ing research by Dr. Bob Niel
sen, extension com agronomist
at Purdue University, indicat
ing that field drydown may
result in significant yield
losses.
Dr. Nielsen reports that he
has observed a 1 percent loss in
dry weight for every point of
moisture dry down, and adds
that if you’re talking about let
ting com dry down 10 percen
tage points in the field, you’re
talking about a 10 percent yield
loss.
Yield losses during field dry
down have usually been asso
ciated with ear droppage, stalk
lodging, pest injury (for exam
ple, ear rots, animal feeding)
and mechanical factors (that is,
shelling at the combine head).
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moisture for com is generally
considered to be 25 percent
(with mechanical damage to
kernels increasing above 25
percent and mechanical harvest
losses increasing below 25
percent).
However, Dr. Nielsen
believes that additional yield
loss may occur above and bey
ond mechanical harvest loss
due to continued kernel respira
tion (metabolic consumption of
carbohydrates in the seed with
the concurrent release of car
bon dioxide and water) after
physiological maturity (black
layer).
“The embryo (in the seed) is
still alive and using up fuel or
energy causing weightreduc
tion.” Physiological maturity is
defined as the time when the
com kernel reaches its maxi
mum dry matter content. The
moisture content of the kernel
at physiological maturity varies
with environment and hybrid
but usually averages 30 to 35
percent.
Previous research indicated
that once a com kernel reached
physiological maturity it would
only lose water (as it dries
down) without loss of yield.
The Farm Journal article also
cited reports from growers and
a seed company corroborating
what Bob Nielsen has
observed. However, some of
my counterparts in other states
have performed similar studies
to determine kernel dry matter
loss during drydown but have
not observed yield reductions.
The article noted that some
hybrids may be affected more
by post maturity “respiration”
than others.
In a past Purdue report. Dr.
Nielsen noted that these kernel
dry weight decreases with dry
down do not occur consistently.
Field drydown after physiolog
ical maturity affected kernel
dry weight in only 1 of 4 years
(1985-1989) for a hybrid wide
ly grown in the mid-’Bos.
These findings would sug
gest that varying environmental
conditions during maturity
might also influence this
phenomenon.
iron
[anese
calcium
boron
Tie (ffvwmp People
(Continued from Pago 21)
Pursuit
resistant com hybrids arc still
relatively new but several var
ieties adapted to the Northeast
are available this year and the
cost is only about $1 per acre
more than ordinary com seed.
Birdsfoot trefoil and crown
vetch seedlings are so resistant
to Pursuit that com can be over
seeded with these legumes at
com planting time with Pursuit
applications made safely at or
after com emergence.
Pursuit is weak on common
ragweed, common lambsquar
ters, and most annual grasses
except the foxtails but these can
be controlled with the addition
of a new herbicide called Basis.
Ten fanners identified by
county agents, crop improve
ment association scouts, or
nutrient management techni
cians working for the county
conservation districts initially
indicated an interest in estab
lishing demonstration fields of
a crownvetch/birdsfoot trefoil
living mulch in 1995. To make
the input costs more attractive,
the crownvetch and birdsfoot
trefoil seed was supplied for
half the cost (about $7.50/acre)
for farmers who were interested
in putting out demonstration
plots about 10 acres in size.
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The Field
You get a fine, uniform chop with the Model 790
forage harvester from New Holland. The 12-knife
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Nobody builds forage harvesters better than
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provided three units of imida
zoiinone resistant (IR) com for
the same demonstration plots.
American Cyanamid provided
Pursuit in packets that covered
exactly 10 acres. The total cost
of these inputs was about
$3O/acre less than the fanners
would otherwise have had to
pay. All other inputs such as
fertilizer were paid by the far
mer. This year only the cover
crop seed and Pursuit will be
supplied at half the cost.
Our experience during the
establishment year was gener
ally good. At most sites, we
achived good weed control and
stands of the birdsfoot/
crownvetch mixture. At each
site we hope to be able to come
back in with no-till com next
year and supress the cover crop
enough to get good com yields
and still maintain the cover
crop.
I expect that, over time, the
birdsfoot trefoil will die out and
we will be left with a predomi
nately crownvetch cover crop.
Any farmers interested in
trying this living mulch system
this year should contact their
local county agent, crop man
agement association scout, loc
al Natural Resource Conserva
tion Service representative, or
call Dr. Nathan Hart wig at Penn
State University (814)
865-1906 for more
information.