Crop conditions have varied dramatically in 2013 across the Corn Belt, and Iowa is no exception. This year Iowa, the nation's leading corn producer, sits in a rare position in terms of yield potential—lower than several other Corn Belt states. Iowa once again leads in total amount of corn produced, but not in bushels per acre--not this year.
Roger Elmore, Iowa State University Extension corn agronomist, writes the "Corn Source" column each month in Wallaces Farmer magazine. He offers the following observations regarding 2013 growing conditions and expected yields this fall.
Iowa conditions were dry in January 2013—even drier than in January 2012. Several articles were written this year by Elmore and his ISU colleagues in the Integrated Crop Management newsletter (available online) that explained their concerns and offered management suggestions for farmers dealing with dry soils. For example, plant population changes; hybrid changes; soil management; and planter adjustments.
Extreme heat that hit in late summer during grain fill period hastened crop development, but reduced yields
"March and April rains this spring, and the snow, relieved our concerns about drought continuing from 2012," says Elmore. "In late April of 2013, a few days of good planting conditions encouraged Iowa farmers to plant 2% of their acres in late April. Early May snows hampered planting for some time and conditions continued to be wet and cool. This year, only half of Iowa's corn was planted by mid-May. That was in dramatic contrast to 2010 when half of the state's corn was planted by April 18."~~~PAGE_BREAK_HERE~~~
Half of Iowa's 2013 corn was silked by July 28 (see Figure 1), in contrast to 89% for the 5-year average and 99% in 2012. Although conditions around silking time were reasonable and likely resulted in good kernel set, the hot, dry conditions which occurred after that and continued into mid-September reduced the yield potential, notes Elmore. Heat unit accumulations ranged above normal during a several week period, hastening crop development and likely reducing yields.
Figure 1. Percent of corn rated good and excellent across the Corn Belt during the 2013 growing season. Columns starting from the left for each state are for reports issued weekly from June 2 through Sept. 15, 2013, respectively. Crop condition data were compiled and adapted from USDA-NASS Quick Stats. The single yellow column among the blue columns for each state represents the first week at which 50 percent or more of the crop was silked based on USDA Crop Progress data. The first number in the rectangles overlaid over the columns for each state indicates that state's final 2012 USDA yield. The number to the right in each box is the September 2013 yield forecast for that state. Yield data are derived from the USDA-NASS September 2013 Crop Production report. Full-size image
USDA's National Ag Statistics Service publishes crop condition reports for major corn-producing states weekly in its Crops & Weather bulletin, available online. The crop condition segment of these reports derives from subjective data, notes Elmore. Subjective data are based on opinions of volunteers who survey crop conditions weekly and report their findings. Subjective data are more open to interpretation and may possibly be influenced by emotions.~~~PAGE_BREAK_HERE~~~
"On the other hand, objective data, like that which the USDA-NASS yield forecasts are based upon, are in large part fact-based, measureable, quantifiable and repeatable," he explains. "With this understanding, USDA-NASS uses the following criteria to rate crop conditions subjectively during the growing season."
* Very Poor - Extreme degree of loss of yield potential, complete or near crop failure. Pastures provide very little or no feed considering the time of year. Supplemental feeding is required to maintain livestock condition.
* Poor - Heavy degree of loss to yield potential that can be caused by excess soil moisture, drought, disease, etc. Pastures are providing only marginal feed for the current time of year. Some supplemental feeding is required to maintain livestock condition.
* Fair - Less than normal crop condition. Yield loss is a possibility but the extent is unknown. Pastures are providing generally adequate feed but still less than normal for the time of year.
* Good - Yield prospects are normal. Moisture levels are adequate and disease, insect damage and weed pressures are minor. Pastures are providing adequate feed supplies for the current time of year.
* Excellent - Yield prospects are above normal. Crops are experiencing little or no stress. Disease, insect damage and weed pressures are insignificant. Pastures are supplying feed in excess of what is normally expected at the current time of year. You can access these weekly Crop & Weather reports here.
Iowa corn conditions—correlated with reduced yield forecasts for 2013
"For most of us in Iowa, it was no surprise to see our corn crop conditions slide weekly for 10 weeks from early July through mid-September," says Elmore. That slide is shown in the chart accompanying this article (see Figure 1). By mid-September, only 35% of Iowa's crop was rated in either the 'Good' or 'Excellent' categories. "That suggests only 35% of Iowa's crop was expected to yield normally or greater than normal," he says. "On the other end of the scale, 28% of the crop rated 'Poor' or 'Very Poor' in mid-September, which means that expectations for these crops are for 'heavy' or 'extreme' losses in yield potential."~~~PAGE_BREAK_HERE~~~
September's USDA-NASS corn yield forecast of 162 bushels per acre for Iowa is nearly 17 bushels below the 30-year trend line – a 9.4% reduction from Elmore's 2013 trend line yield estimate of 178.9 bushels per acre. Of course, that still sounds better than last year's yield of 137 bushels per acre for Iowa! "Be aware though, that these crop condition data are summarized as state averages," he points out. "Obviously, conditions range widely in Iowa as reflected by September's USDA-NASS yield forecast."
Corn Belt corn conditions and yield forecasts for 2013; Iowa is fortunate to have the yield that is currently forecast
Corn growing conditions also varied widely across the Corn Belt during the 2013 growing season, as the accompanying graph shows. While Iowa's corn conditions fell for 10 straight weeks, Missouri's fell for five weeks and Wisconsin's nine weeks, notes Elmore. These three states all have less than half of their acreage in good and excellent condition and thus should expect to harvest below trend line yields this fall, based on subjective data from the crop condition reports. Iowa's September forecast yield is 9.4% below the trend line. September yield forecasts for Missouri, at 125 bushels per acre, and Wisconsin, at 143 bushels per acre, are the lowest among the state's that are shown in Figure 1.
On the other hand, Illinois and Minnesota ratings currently are between 50% and 60% good and excellent, he notes. They might expect normal yields. Although ratings fell for several weeks in Indiana, Nebraska and South Dakota, their good and excellent ratings remain at or above 60%. Corn conditions in Ohio hovered above 70% good and excellent all season. You can expect to see very good yields in 2013 from Ohio! The USDA's September 2013 yield forecasts across the Corn Belt seem to correlate with crop condition reports after silking, as shown in the accompanying graph.
"Considering the kind of weather year Iowa corn experienced this year, we are fortunate to have a forecast yield that's as high as it is at this time," sums up Elmore. "Modern corn hybrids, improved management systems and Iowa's excellent soils certainly pay off in a stressful year like 2013."