GROWING DEGREE
DAYS AND
LATE PLANTED CORN
Greg Roth
Penn State Agronomy
Assistant Professor
At the recent American Seed
Trade Association annual com
and soybean conference,
Purdue agronomist Bob Niel
sen recently reported his find
ings on a study that evaluated
the effect of planting date on
growing degree accumulations
for com.
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This research showed that
when planting was delayed
from early May to early June,
the growing degree days
required for hybrids to reach 50
percent silk and black layer
decreases. Growing degree day
requirements to 50 percent silk
were reduced by an average or
64 GDDs and later plantings
tended to have 1 to 2 fewer
leaves.
Growing degree day require
ments during the grain fill
phase were also reduced fron\Q
to 9 GDD per day of planting
day delay.
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Overall ODD requirements
from planting to black layer
were reduced from 2 to 10
ODD per day of planting delay.
If we assume an average reduc
tion in the GDD requirement of
about 5 GDD per day, then a 40
day delay in planting would
reduce the GDD requirement
from 2700 GDD for a full sea
son hybrid in late April to 2500
GDDs in early June.
What does all this mean? It
means that hybrids seem to
adjust somewhat to the shorter
season by reducing the amount
of GDDs they need to mature. It
also means that we may not
Mercer County Lists Crop Yields
MERCER (Mercer Co.)
Following are the results of
several area com plots that
were received at the extension
office over the last couple of
weeks.
Some of the plots are com
pany demonstration plots and
Brand/Hybrid
Pioneer 3845
Agway 454
Agway 310
Pioneer 3751
Doebler 52XP
Doebler 55XP
Pioneer 3525
Doebler 57XP
Pioneer 3394
Doebler 64XP
Agway 578
Doebler 62XP
Doebler 66XP
Doebler 73XP
Doebler 75X
Doebler 69XP
Average
Corn Talk, Lancaster Farming, Saturday, February 11, 1995—Page
necessarily need to switch to
hybrids as early as GDD
requirements might dictate.
The experience of growers and
seedsmen I’ve talked to appears
to support this concept. Our
research in Pennsylvania has
shown similar results with one
difference. Here, hybrids will
mature in fewer GDDs than
they are rated at even when
planted in early May. For
example, in a two year study we
conducted, a hybrid rated at
2850 GDDs matured in two
seasons at 2621 GDDs in Lan
caster County.
At Rockspring, when we
some have hybrids from sever
al different companies in them.
These should not be taken as an
endorsement of any one hybrid
or company over another, but
only as information that may
help you in making the right
decisions in your com produc-
% Test
Moisture Weight
Yield @
15.5%
144.0
145.6
156.4
174.3
175.7
155.2
179.9
153.8
208.7
178.3
157.0
186.8
182.8
170.1
172.0
172.4
Income
296.56
294.52
316.36
351.58
351.38
303.72
350.49
296.65
399.15
336.68
291.67
345.29
337.14
306.80
305.75
302.31
TSS3S 324.13
delayed the planting of three 92
to 97 day hybrids for 20 days,
they required about 125 GDDs
less than in early May. This
translates into about 6 GDD/
day of planting date delay, con
sistent with the results of the
Purdue study.
These results indicate that
GDD requirements are only a
rough guide to predicting
hybrid maturity since they vary
somewhat depending on loca
tion and planting date. Also,
ratings of hybrids conducted in
the midwest often overestimate
the requirement in Pennsylva
nia by about 200 GDDs.
tion for next year.
Cooperator: Jim Woods
County; Mercer
Planted: 5/3/94
Harvested; 11/9/94
Harvest Population: 23,400
Row Width: 30”
Previous crop: Com
Fertilizer: 19-38-38
Manure: 12-15 ton liquid/acre
Herbicide: Prowl, + Atrazine, +
Harness
211