"The small percentage of the crop planted late this year suggests
that the U.S. average yield will be higher than if a normal
percentage had been planted late, but the level of yields is still
to be determined," said Darrel Good.
Good said that the small
percentage of the crop planted late this year and the early
conditions of the crop point to the potential for an above-trend
yield in 2012, but the most important part of the season is just
"The corn market will continue to follow weather developments and
crop condition ratings in order to refine yield expectations," he
said. "At this juncture, two important developments may be required
in order to maintain high yield expectations. The first is some
convincing evidence that the relatively long period (eight months or
so) of above-average temperatures is giving way to normal or
below-normal temperatures. The second is for soil moisture deficits
in important areas of the central, eastern and southern Corn Belt to
Good said a second piece of early information relative to corn
yield potential is the crop condition rating provided in the USDA's
weekly Crop Progress report. He said there has historically been a
positive relationship between the percentage of the crop rated good
or excellent at the end of the season and the U.S. average yield
relative to trend.
"Early crop condition ratings are suggestive of yield potential,
but ratings can, and do, change substantially by the end of the
season," Good said. "The first crop condition rating of the season
this year showed that 77 percent of the crop was in good or
excellent condition as of May 20.
"Since 1986, an average of only 66 percent of the crop was rated
in good or excellent condition in the first report of the season,"
Good said. "There were only six other years when the initial ratings
showed 75 percent or more of the crop in good or excellent
condition. The rating at the end of the season was higher than the
initial rating in two of those years (1987 and 1994), and the U.S.
average yield was well above trend in both years. The rating at the
end of the season was below the initial rating in four of the six
years. The average yield was near trend value in three of those
years when the final ratings showed 60 to 69 percent of the crop in
good or excellent condition. The U.S. average yield was well below
trend in 1991, when the final rating showed 53 percent in good or
What do we know about yield potential as the summer growing
The most important development to date, Good said, is the timely
planting of the crop. There is a relatively wide window of planting
dates for maximum corn yield potential, with yield penalties
associated with late planting.
[to top of second column]
"Since corn planting dates vary considerably by geographic area,
corn planting occurs over a period of several weeks, and has been
occurring earlier over time, there may be a number of ways to
characterize timeliness of planting on a national basis," Good said.
"For the period beginning in 1986, we defined late planting as
the percentage of the crop planted after May 20 in the major
corn-producing states that are included in the USDA's Crop Progress
report," Good said. "This year, only 4 percent of the corn crop in
the 18 major corn-producing states was planted after May 20. That is
the smallest percentage of the crop planted late during the 27-year
period since 1986."
Good reported that, on average, 18 percent of the crop was
planted after May 20 from 1986 through 2011. There were nine other
years when less than 10 percent of the crop was planted after May
20. In those nine years, the U.S. average yield was within two
bushels of the trend yield in five years.
Good said large deviations from trend yield occurred in the early
planted years of 1987 (up 8 bushels), 1988 (down 29 bushels) and
1992 (up 16.8 bushels).
"These yield results are not especially informative for
developing expectations about the average yield in 2012," Good said.
"With all else being equal, the planting date may be important for
yield potential, but summer weather conditions ultimately determine
the level of yields."
In addition to yield prospects, Good said the expected size of
the 2012 crop will be affected by the magnitude of planted and
harvested acreage. The USDA will provide survey-based estimates in
the Acreage report to be released on June 29. New-crop corn prices
are expected to remain under pressure as long as large crop
[Text from file received
from the University
of Illinois College of Agricultural, Consumer and Environmental