Page 20—Corn Talk, Lancaster Farming, Saturday, February 13,1993
Greg W. Roth
Department of
Agronomy
Penn State
Much has been happening in
the area of com production
research at Penn State and some
of our neighboring institutions.
The purpose of this paper is to
provide a brief overview of
some of the results of this
research that you may find use
ful in your operation.
This overview will focus on
cultural practices and hybrid
selection. The research areas
that will be discussed will
include silage yield and quality
studies, com/sorghum compar
isons, tropical hybrid evalua
tion, plant population research,
row cleaning devices, effect of
cultural practices on root
worms, stability analyses, and
com maturity studies.
Silage Yield
And Quality
For the past three years, we
have been evaluating effect of
hybrids, plant populations, and
harvest date on silage yield and
quality. Our hybrid studies
have focused on determining
whether or not some widely
grown hybrids vary in silage
quality as much as some reports
have indicated in the literature.
Also, we wanted to evaluate
how consistent these differ
ences were over a wide range of
locations, because com silage is
produced under a wide range of
conditions in Pennsylvania,
unlike some other areas.
We used nine
hybrids and grew
them in four different
tests in 1990 and
1991. We found that
hybrids did vary for
quality, but not that
much. Variations in
digestibility and pro
tein were greatest.
Digestibility differ
ences ranged up to 1.8
percent and protein
differences ranged up
to 0.5 percent. The
variation in ADF and
NDF was not signific
ant between hybrids
when averaged over
locations. On a per
centage basis, yield
varied much more
than quality. We con
clude that yield differ
ences are most impor
tant and should con
centrate on belter
testing for silage
yield. Quality differ
ences exist, but there
appears to be some
uncertainly about
what to measure. Our
data suggests that
digestibility measure
ments may discrimi
nate between hybrids
better than traditional
quality measurements
like ADF and NDF.
Penn State’s Corn Research Results
Comparisons of different
populations and harvest dates
have indicated that silage were
maximized near populations of
25,000 plants per acre with
population having little effect
on quality. Ourharvest date stu
dies have shown that for
harvesting for silage in the
63-68 percent moisture range,
harvest should occur between
full dent and half milk in the
kernel. We have found that
maximum yields are obtained
near half milk. Waiting to
harvest silage until black layer
results in silage that is too dry
and increases the risk of molds
in the silage.
Corn/Sorghuin
Comparisons
We have been evaluating
grain and forage sorghums as
potential replacements for com
in areas with drought stress
potential and deer damage
potential. To date we have con
ducted five side-by-side com
parisons. The sorghums are
more drought tolerant and also
resist damage from deer.
In three of the strip trials, the
deer ate the com right to the
ground. In two others, the dam
age to the com was more typi
cal with most of the ears
removed. Results of a typical
trial are shown in Table 1.
Table 1. Performance of forage
sorghum, grain sorghum and
three com varieties grown
under moderately heavy deer
pressure in Centre County in
1991.
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Com/Doebler’s 45 X
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Based on the results of these
trials, I conclude that forage
sorghum is a good alternative
under these situations. Early,
medium height forage sorg
hums that set a lot of grain
appear to be a good choice for
many of these situations. They
resist deer damage even better
than the grain sorghums, have
low risk of lodging, produce
good silage yields of reasonab
ly good quality, mature before
frost reducing the risk of
prussic acid and give the grow
er the option to harvest for
grain.
Tropical Hybrid
Evaluations
Interest in the success of
using these hybrids as double
crop alternatives in the South.
There, agronomists have found
that some tropical hybrids do
exceptionally well when
planted late, when normal com
is often devastated by fall
armyworm. Locally, some
growers have been attracted to
T/A %
11.01 61.8 35,1 64.6
6.28 78.5 25.4 72.3
4.65 42.9 36.5 61.3
4.71 65.2 37.5 60.6
5.30 68.3 33.0 63.7
these because of their height
and seemingly large silage
yield potential. In 1992 we
compared the yield potential of
a normal com hybrid, a tropical
hybrid com and an open polli
nated silage com in three grow
ing environments. As expected
Yield Harvest Yield Harvest Yield Harvest
Com
21.0 9.16 14.9 a 10/20 19.7 a 10/5
19.5 ab 10/20 11.1 b 10/20 17.4 ab 10/12
17.7 a 9/29 14.0 b 10/12
Normal
Tropical
Open poll.
Yields within a column fol
lowed by the same letter are not
significantly different.*Double
crop com was planted July
I.Plant population research
Population research prog
rams are currently under way at
Cornell, Ohio State, and Wis
consin. The Cornell program is
far enough along so that recom
mendations are being revised.
They are suggesting plant
populations up to 28,000 ppa
where com is grown for grain
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the tropical and the open polli
nated were tall and late. The
open pollinated was also prone
to lodging, but the tropical
hybrid stood well, even though
it was twelve feet tall. The trop
ical hybrid was susceptible to
smut and had poor early season
growth. Yields of both the open
pollinated and the tropical were
less than the normal silage com
(Table 2).
Based on the results of these
experiments, tropical and open
pollinated silage corns do not
appear to be competitive with
top performing conventional
hybrid corns.
Table 2. Yield and harvest date
of a normal hybrid, tropical
hybrid and open pollinated sil
age variety in three environ
ments in 1992
on good soils. They suggest up
to 30,000 plants on good soils
for silage. For less productive
soils, plant populations should
be reduced.
In the Ohio State research,
populations, N rates, and
hybrids are being compared.
There, com yields respond only
when moisture was adequate
and the full recommendation of
N was applied. This occurred in
one of three studies. A recent
Univ. of Wisconsin study com-
(Turn to Page 21)
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