The results of the Iowa Agriculture Experiment Station
Corn Yields are presented annually as a service to
Trials were planted at 23 locations
and data were obtained at 21 locations in 2002.
Planting dates ranged from late April to mid May with seedbed conditions
variable among locations because of moist conditions in late April and early
May. Harvesting was completed later than
in recent years because weather conditions delayed harvest in some areas. The dates of planting and harvesting for each
trial are shown in the title of each table.
Conditions for planting, emergence, growth, and development in 2002 were
generally favorable after planting at most locations. Dry, warm conditions occurred in the southern
and western edges of the state during July and August and affected yields at
the southern and western locations. Yield
data were not obtained at Lewis because extreme dry conditions limited plant
and ear development; grasshopper feeding also was extensive at Lewis. Data were
not obtained from
Plots generally were 18 feet long
and included two rows spaced 30 inches (90 sq. ft. per plot) at most
locations. There were minor variations
in plot length among locations, and the differences in plot size were
considered in yield conversions. Actual
plant stands for each hybrid are shown in the 1000’s (M/ha) of
plants/hectare. The plant stands can be
converted to plants/acre by multiplying with a factor of 0.4 (e.g, 67,000
plants/ha x 0.4 = 27,080 plants/acre).
Seedbed preparation, fertilizer application, and cultivation practices
were those normally recommended for optimum corn production at the locations
where the trials were grown.
All trials were planted and
harvested with equipment adapted for planting and harvesting small experimental
corn plots. There was no gleaning of
either dropped ears or ears on broken stalks at harvest, but data for stand and
root and stalk lodging were recorded before harvest. Harvest losses because of root and stalk
lodging and dropped ears are reflected for hybrids at the sites where lodging
and dropped ears occurred. Root lodging
occurred at most sites in 2002, and was severe at some locations and for some
specific hybrids. Rainstorms accompanied
by strong winds occurred at some locations during July and August and local
hailstorms affected some locations. Root
lodging was more severe at Pocahontas, Waverly, Kanawha, Carroll, Crawfordsville,
and
Planting of ISU trials started April
23, 2002 at Ames, and all locations were planted by May 6, 2002. Planting dates for the cooperators were
similar to those for the ISU trials.
Harvest of the ISU trials started later in 2002 than in previous four
years. Because of cooler, wetter
conditions in September and October, corn matured slower and grain moistures at
harvest were generally higher than for recent years, particularly in northern
Iowa. Harvest of ISU trials started
October 7 at Ames, and harvest was completed October 23 at Calumet. The cooperators had similar dates of
harvest. Conditions were generally good
during harvest throughout the state, but harvest interruptions did occur
because of either local rains or snow showers.
The quality of data varied among locations because of the incidence of
extensive root lodging at some locations. Weather
and pests usually have important effects on corn evaluation trials. These effects are not predictable and the
ranges of conditions experienced were evident in 2002. The major weather factor at some locations
was limited rainfall and warm conditions during July and August after a wet May
and June. Some locations were affected
by more windstorms (e.g., Ankeny and Kanawha) than others but root lodging was
greater than normal at most locations.
Weather conditions during anthesis were generally warm and dry, but
timely rains during pollination occurred at most locations. At Ames, for example, excellent rains
occurred July 10 (3 inches), July 12 (2 inches), July 27 (0.6 inch), and August
3 (1.5 inches). Although it was warm
during pollination, the timely rains minimized stress conditions for pollen
shed and silk emergence.
Single crosses tested were produced
between lines released by ISU and other states.
Because fewer lines are being released by other public breeding
programs, fewer single crosses that included lines released from other states
were available for testing. Data are
presented for the lines that have experiment station designations and for a few
experimental lines from the ISU breeding program that have survived testcross
and initial single-cross evaluations. We
have included data for each of the 2002 locations, data averaged over locations
for the three sets (5 locations for earlier maturity, 5 locations for mid-maturity,
and 13 trials for later maturity) of trials, and 3-year averages for each
location. Three-year averages are more
reliable for comparing hybrid performance.
Yields are given in quintals/hectare (q/ha). Yields in bushels/acre are obtained by
multiplying the values in the tables by a factor of 1.6 (e.g., 90 q/ha x 1.6 =
144 bu/acre). We have included a column
in the tables designated as adjusted value.
Adjusted value is the value in dollars per acre assuming $2.00 per
bushel for corn, 1.35% shrinkage, and $0.035 per bushel per point drying cost.
Single-cross trials conducted at 23
locations included 10 locations handled by ISU and 13 handled by commercial
plant breeders. Data were obtained for
all locations except for the ISU trial at Lewis. Data from additional locations provide a
better basis for discriminating among hybrids for consistency of
performance. Least Significant
Differences (LSD values) are shown at the bottom of each table. LSD values for means across locations were
calculated using the location by hybrid interaction mean square. Differences among hybrids are due to genetic
differences, variations in soil type, soil fertility, moisture availability,
temperature stress, insect and disease pressures, and planting and harvesting techniques. Differences among hybrids greater than the
LSD value can be attributed to genetic differences; differences less than the
LSD value are not statistically different and could be due to other factors.
ACKNOWLEDGMENTS
We wish to acknowledge the following individuals and
their respective organizations for assisting us in conducting the 2002
single-cross trials.
Individual Organization Location
of test
Kermit
Bohning Mycogen Conrad
Dwight
Bostwick Novartis
Seeds Harlan
Philippe
Chartier Pau Seeds,
Inc. Waverly
Dan
Currier IFS Clarion
Arlen
Eggerling Hawkeye Hybrids,
Inc. Pella
Bill
Forgey Pau
Seeds, Inc. Tingley
Jon
Geadelmann Holdens
Foundation Seeds Cannon
Falls, MN
Bob
Getschman Monsanto
Global Seeds Pocahontas
Duane
Grensteiner Golden
Harvest Estherville
Kory
Maughan Golden Harvest Stanhope
Robert
Miller Novartis
Seeds Washington
David
Peters Monsanto
Global Seeds Atlantic
Lance
Veldboom Holdens
Foundation Seeds Williamsburg