August 1, 2019 / 6:38 AM / 4 months ago

Column: Cool start to August may not benefit lagging U.S. corn crop

FORT COLLINS, Colo. (Reuters) - In a normal year, about three-quarters of U.S. corn would be reaching maturity exactly two months from now. But given that an unprecedented portion of the 2019 crop was planted very late due to heavy spring rains, this and a cool August forecast could prevent some corn from crossing the finish line.

FILE PHOTO: Corn is loaded into a truck at a farm in Tiskilwa, Illinois, U.S., July 6, 2018. REUTERS/Daniel Acker/File Photo

July was warmer than normal across most of the U.S. Corn Belt, especially in the eastern portions where planting delays were the worst. A warm July is not normally favorable as pollination usually kicks off the month, but it was seen as helpful this year with the crop so far behind in development.

The U.S. Climate Prediction Center on Wednesday published its temperature outlook for August, showing a cool bias is likely for the entire Corn Belt. Normally, that would be a favorable forecast for grain filling, and it is difficult to alarm market-watchers over a cool August when excessive heat is usually the issue.

Corn needs a certain number of growing degree days, or GDDs, to move through the growth cycle from planting to maturity. GDDs are a measure of heat accumulation and can help growers predict stages of the crop, and for corn they are accumulated at temperatures between 50 and 86 degrees Fahrenheit (10 and 30 degrees Celsius).

Since May 1, the Eastern Corn Belt is ahead of normal on GDDs but the Western Belt is behind. Iowa has accumulated about 95% of normal GDDs during the period, while Nebraska is at 90%. Illinois is at 101% of normal and Indiana is further ahead at 104%.

But a lot of the corn was planted much later than normal this year, especially in the eastern areas. According to the U.S. Department of Agriculture, some 56% of the Illinois corn crop had yet to be planted on June 1, and Indiana and Ohio were even further behind with 70% and 69% left to plant, respectively. Ohio still had 35% of its corn to plant on June 15 while Indiana had 18% and Illinois 14%.

On average, corn planting passes 90% complete around May 20 in Illinois, May 29 in Indiana, and June 2 in Ohio. While the planting progress data does not guarantee a certain number of acres were planted, it was clear by both the data and ground reports that a record portion of the crop was planted late in these states.

Nationally, some 42% of the corn was still waiting to pollinate as of Sunday when normally only 17% would be left. Silking progress was 44 percentage points behind the five-year average in Indiana, 43 points behind in Ohio, and 50 points back in South Dakota. That is a wider margin from average compared with two weeks earlier, despite warmer temperatures in the east during the period.

Full-season corn generally needs around 2,700 GDDs from planting to maturity, but short-season varieties can require as little as 2,300. If temperatures were completely average in August and September, corn planted on June 8 in the northern parts of Illinois, Indiana and Ohio would reach about 2,340 GDDs by Oct. 1. Corn planted on June 15 would have about 2,230 GDDs by that date.

Research conducted by Purdue University several years back suggests that most corn varieties can adjust their GDD needs when planted late, requiring fewer units to reach maturity, though a lot of this year’s corn was planted later than the dates tested by that study.

As summer turns to fall, GDDs accumulate at a much slower rate as temperatures near or below 50 degrees F are common. In northern Illinois, for example, only about 140 GDDs are normal for the whole month of October.

On average over the last five years, about 74% of U.S. corn reaches maturity by Oct. 1. Just below 50% of the 2009 crop reached maturity by that date after a slow planting campaign and a cool growing season.

Although risky, temperatures around 32 degrees F (0 C) are not always fatal to corn, but death is much more likely when the temperature falls to 28 degrees F (-2.2 C). According to the Midwestern Regional Climate Center, a large portion of Illinois and Indiana typically observes its first 28-degree reading in the last 10 days of October, though the middle 10 days are also likely for those states as well as for much of Iowa.

Despite the late-maturing corn, an extremely long harvest, and high drying costs for producers, the 2009 crop is also remembered for its record-high yield and production. Yields are not expected to come anywhere close to record in 2019, but if the crop ends up mostly making maturity with minimal production loss as a direct result, the failure to achieve maturity may never again be a concern to the market.

Editing by Matthew Lewis

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