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Copyright 2005, Board of Trustees, University
Agricultural Research Center November 1983
Research Report RC-1983-8
COMMERCIAL CORN VARIETY TEST RESULTS
FROM SOUTH-CENTRAL FLORIDA, 1983
P. Mislevy, R. S. Kalmbacher, P. H. Everett and E. S. Homer
Corn can be extremely valuable in a livestock feeding program. With
its rapid growth and high yielding ability, corn harvested kA4e&reL RARY
silage can supplement perennial grasses at times when the r pro4dtijkd (65
low. Corn may follow winter vegetables or be used in a p .St .rey. tioForida
program. High quality corn silage can provide dairy and beef cattle with a
substantial carbohydrate input, possibly reducing high grain costs and
providing growing calves with quality feed.
Well managed corn harvested for silage at the proper state of maturity
can produce 7 to 12 t/acre of dry matter in a 3.5 to 4.0 months. This
would allow the land to be free for the growth of other crops during the
remaining eight months.
Corn silage harvested at the hard dent stage usually contains 30 to
40% dry matter, 8% crude protein and is high in energy, carotene, vitamin
D, but low in minerals. To produce high yields of quality corn forage,
adapted hybrids, proper seeding date, high fertility, water control,
correct plant populations, and weed, insect and disease control are
1/ Professor and Associate Professor, respectively, Agricultural Research
Center, Ona; Professor, Agricultural Research Center, Immokalee;
Professor, Agronomy Department, Gainesville, Florida.
The purpose of these studies was to evaluate commercial corn hybrids
for silage and/or grain production at Ona and Immokalee.
The experiments were conducted at the Agricultural Research Centers
(ARC) at Ona and Immokalee. The experimental design at both locations was
a randomized complete block with 4 replications. Twenty seven commercial
corn varieties were seeded at Ona and twenty at Immokalee. The experiment
at Ona was seeded on Ona fine sand on April 4 and reseeded April 19, 1983.
The Immokalee experiment was seeded on Immokalee fine sand on February 8
and reseeded on February 25 and again on April 4.
Fertilization practices at Ona were 980 lb/A of 0-10-20 (N-P205-K20) +
20 lb/A FTE 503 micronutrients prior to seeding. One ton/A of dolomite was
applied to maintain pH and supply Ca and Mg. Nitrogen was applied at a
rate of 130 Ib/A pre-emergence, and 80 Ib/A when corn plants were 24 inches
At Immokalee 50-50-100 lb/A of N-P205-K20 with 20 lb/A FTE 503 was
applied and disked into the seed bed prior to seeding on February 8. No
fertilizer was applied before reseeding on February 25, but 50-45-90 lb/A
of N-P205-K20 was again applied when the experiment was reseeded for the
third time on April 4. On April 29, when corn was 10 inches tall,
120-50-50 lb/A was applied, and on May 17, when corn was 22 inches tall,
100-50-50 was applied. Micronutrients were applied on May 11 as a foliar
spray to help correct yellowing.
Plant populations and pest control
Corn at Ona was seeded in 30 inch rows and adjusted to a final
population of 26,000 plants per acre. In Immokalee the corn was seeded in
30 inch rows and adjusted to 25,000 plants per acre. Herbicide practices
used at Ona were 2.0 lb/A atrazine (active) and 2.0 Ib/A Lasso(R) (active)
pre-emerge in 35 gallons of water per acre. No cultivation practices were
employed after the corn was seeded. The insecticide Dasanit(R) 15 G (2.0
lb active/A) was applied in a 7 inch band at seeding, to control soil
insects. The insecticide Mesurol(R) was applied on the seed at the rate of
1 lb commercial product/100 lb seed to repell birds.
At Immokalee AAtrex(R) was applied at 2.0 lb active/A in combination
with Lasso(R) at 2.0 lb active/A at the first seeding. Lasso was reapplied
at 2.0 lb/A at the April 4 reseeding. Furadan 10 G was applied at 10 lb/A
(active) in the row at each seeding. Mesurol(R) was applied at the same
rate used at Ona. Corn was sprayed with Lannate 1.8L(R) on April 15 and 21
and May 10 at 2 pints/100 gal. of water to control bud worms.
A total of 2.6 inches of water was applied using over-head sprinklers
at the Ona ARC. The Immokalee experiment was irrigated by a seepage system
with laterals on 40 foot centers.
Corn maturity at harvest
Corn was harvested when the kernels were at the hard dent stage as
recommended for silage production. This was coincidental with black layer
formation at the base of kernel in most varieties. The experiments were
also harvested for grain. All values were converted and expressed in
bushels of shelled corn at 15.5% moisture.
Results and Discussion
Forage dry matter yields of commercial corn hybrids grown at Ona
during the 1983 growing season were very good averaging 8.0 t/A (Table 1).
These yields ranged from a high of 10.6 t/A for Northrup King 'PX 9692' to
a low of 6.3 t/A for 'Coker C 19'. The 1983 corn experiment was delayed in
seeding by about 45 to 50 days due to excessive soil moisture.
Consequently, the corn was not seeded until April 19 and harvested July 27,
1983. As a result, corn was mature (average 50.0% forage dry matter) and
ready for harvest in only 99 days due to the high temperatures of May, June
and July. Corn matured about 20 to 25 days earlier than plants seeded at
the normal February 20 to March 10. Dry matter ranged from a high of 59.3%
for Paymaster UC-7251' to a low of 43.5% for Dekalb 'XL 395 A'. The
ability of top yielding hybrids to dry rapidly is a very desirable
characteristic. Fast drying indicates that a variety would be ready for
ensiling (30 to 40% dry matter) sooner, allowing the producer to remove the
crop before the start of summer rains. Varieties like Ring Around 'RA
1604' and 'Pioneer 7360' have this characteristic.
Growers should also consider using early maturing hybrids like Asgrow
'RX 114' and 'Big D 6986', which mature 7 to 14 days earlier than full
season hybrids, allowing growers to harvest sooner. This allows the grower
additional time for seeding the second crop before summer rains. Early
maturing hybrids generally produce low dry matter yields (Table 1), but
plants dry fast, have low kernel moisture, and have good grain yields and
grain to stalk ratios.
Grain yield is another characteristic to consider when selecting
corn hybrids. Grain yields in 1982 averaged 139.3 bu/A shelled corn
adjusted to 15.5% moisture. Even though the 1983 crop was mature in 99
days, forage (-1.3 t/A) and grain yield (-47.6 bu/A) was reduced
considerably compared with the 1982 crop, which required an average of 118
days to maturity. The highest grain yielding variety in 1983 was Big D
'6986' producing 180.7 bu/A shelled corn. This variety dried relatively
fast averaging 29.2% kernel moisture and 50.5% plant dry matter at harvest.
When selecting corn hybrids for silage an important factor to consider
is the grain to stover ratio. The grain to stover ratio is expressed as a
percentage by weight of grain available in the silage. Corn varieties with
a relatively high forage dry matter yield and low grain yield (Dekalb 'XL
82' or Northrup King 'PX 9692') resulted in a low grain-stover ratio (35-65
or 36-64%) (Table 1). There are other varieties (Funks 'G 4733') that
produced high grain yields and low forage yields (short stalks) resulting
in a 54-46 grain-stalk ratio. When selecting a corn hybrid, choose a
variety with a high dry matter yield, high grain yield and high grain to
stover ratio. Varieties like Pioneer 7360 and Jacques JX 247 are two
varieties that fit these criteria.
Southern corn rust (Puccinia polysora) was not a serious problem
during the 1983 growing season. However, due to the late seeding (April
19) army worm (Spodoptera frugiperda Smith), commonly called bud worm,
damage was greater than normal, especially when plants were greater than 3
Excessive rain and saturated soil resulted in a loss of the first two
seedings made on February 8 and 25. The April 4 planting was successful,
but was about 60 days later than the normal early February planting. Even
with a rim-ditch and lift pump excessive water can still be a major
limiting factor for south Florida corn production. It is unusual for
rainfall to be excessive in late winter, and this was the first time in 8
years of testing corn at Immokalee that the problem occurred.
There were no significant (P<0.05) differences in the dry matter
yields of the twenty varieties tested (Table 2). Yield ranged from 3.6 to
6.9 t/A and averaged 5.5 t/A. Inspite of a relatively large difference in
the range, variability was too great for detection of significant
Varieties producing significantly higher yields in past years were
again superior in 1983 (Ona Research Report RC-1981-10 and RC-1982-6).
Northrup King 508, Dekalb XL 395 A were better yielding full season
hybrids. Inspite of the advantages of early harvest date and high corn
grain to stover ratios, the short season hybrids have yielded well at
Immokalee. Based on test results of 3 to 5 years the full season hybrids
(NK 488, Dekalb 1295, NK 508, Dekalb XL 395 A and Coker 77) have been
better yielding hybrids, especially when compared with the short season
varieties (Table 3).
Fertilization of the trial was designed to produce high yields, but
fertility was still a limiting factor because nutrients were not getting to
the plant when needed. After March, rain ceased and during April and May
there was a protracted dry period. Top-dress applications of N, P, and K
applied to a crop with seepage irrigation do not get into the roots unless
rain or overhead irrigation occur, or unless fertilizer is cut into the
soil. Corn remained in a stunted condition until rain occurred in late May
and moved nutrients into the root zone. The growth that followed these
rains was not enough to compensate for limited earlier growth.
Plant dry matter averaged 38.6% and ranged from 31.6% to 46.7%, and
significant (P<0.05) differences in dry matter were found (Table 2).
Once plants reach physiological maturity, drying occurs very rapidly in hot
There were significant (P<0.05) differences in yield of grain which
averaged 98 bu/A (Table 2). Grain yield was considerably lower than in
other years (Ona Research Report 1981-10, RC-1982-6). Better grain
producers were Dekalb XL 395 A, McCurdy 80-72, Coker 21, Northrup King NK
508, which also yielded more total forage. McCurdy 67-14, Ring Around RA
1604, and Dekalb XL 395 A have been better yielding grain varieties in past
years (Table 3).
Kernel moisture averaged 33.8% and ranged from 28.3% (Pioneer 3165) to
38.9% (Jacques 247)(Table 2). Significant differences in kernel moisture
were found among varieties. Shelling percentage (amount of grain on the
ear) averaged 81.7%. This value ranged from 72.6% (Coker 16) to 88.0%
The grain to stover ratio averaged 46-54 and ranged from 32-68 (Coker
16) to 60-40 (Golden harvest H 2680). Harvest index (grain yield total
crop yield) was 0.46 in 1983, which was lower than that observed in other
years. Average harvest index at Ona and Immokalee during the past 5 years
has been 0.51 and 0.50, respectively. The lower index is probably a
reflection of the late planting date.
Variety selection at Ona and Imnokalee
When considering commercial corn hybrids for forage and/or grain
production in the Ona area it is desirable to select varieties that have
performed consistently well over a three to five year period. Based on
these data Northrup King NK 508, Coker 77 and Ring Around RA 1604
consistently produced 10+ t/A dry matter. However, if grain production was
the objective, Ring Around RA 1604, Jacques JX 247 and McCurdy 67-14
yielded 179, 183 and 183 bu/A, respectively. In the Immokalee area
Northrup King NK 488, NK 508, Dekalb 1295 and XL 395 A and Coker 77 are the
recommended varieties for both forage and/or grain.
When selecting a commercial corn hybrid to be grown and stored as
silage in south-central Florida, it is best to select a variety that
produces high forage and grain yields, resulting in a high (50-50 or above)
grain to stover ratio. Varieties selected should also have a high forage
dry matter percentage and low kernel moisture. If corn hybrids are grown
for grain, then high grain yields at low kernel moisture should be
selected. Kernel moisture is extremely important since it is an indication
of how fast a hybrid dries, allowing for an earlier harvest. In 1983
Pioneer 7360 and Ring Around RA 1604 were two varieties that met these
criteria at Ona. Superior varieties at Immokalee were Northrup King NK
508, Coker 21, McCurdy 80-72 and Dekalb XL 395 A.
Forage and grain
the Ona ARC,
due to saturated
0 Ib/A N-P 05-K20, respe
130 Ib/A N pre-emergence
20 Ib/A FTE
80 Ib/A N w
of water via
* Means within
25 and April
Ib/A of N-P
N-2 5 2
N-P 0O-KO di
Table 3. Average grain and forage dry matter yields of selected varieties
grown at Ona and Immokalee over the past five years, 1979-83.
Grain @ Forage
Brand Variety 15.5% moisture dry matter
XL 395 A
XL 395 A
Based on 3 years data
+ Based on 4 years data
Based on 5 years data