CHICAGO, May 14 (Reuters) - U.S. corn yields are unlikely to reach their full potential this year as the slowest planting pace on record shortens the growing season, increasing risks that plants will pollinate under peak summer heat, agronomists said on Tuesday.
“We have taken some off of our yield potential,” said Emerson Nafziger, extension agronomist at the University of Illinois. “Our preference is to have it in the ground by May 1.”
Nafziger said that based on the last six years of the university’s lab results for Illinois, the No. 2 U.S. corn state, corn planted after May 10 in the state could see a yield loss of 6 percent, after May 20 a 12 percent loss, and after May 31 a 20 percent loss.
Corn grown in the U.S. Midwest grain belt typically starts pollinating in July. Plant growth and yield potential can be reduced if plants are forced to devote energy to staying cool during the hottest days of summer.
Farmers had planted only 28 percent of their intended acres as of Sunday in the United States, the world’s largest producer and exporter. The planting progress was the lowest in records that go back to 1980, according to the U.S. Agriculture Department.
“Most farmers would plant corn in the first few days of June if they had a good chance to get it in in good shape. The yield potential is high enough that you can give up 15 to 20 percent and have a good yield on corn, and good income,” Nafziger said.
Last week USDA forecast this season’s U.S. corn yield at 158.0 bushels per acre, below a projection for 163.6 bpa in February, but sharply higher than the last year’s drought-reduced yield of 123.4 bpa.
Grain processors, livestock feeders, ethanol makers and exporters are all crossing their fingers that U.S. farmers will produce a bumper crop after last year’s devastating drought slashed yields, with supplies forecast as the smallest in 16 years by the end of the summer.
Portions of the U.S. Corn Belt, mostly east of the Mississippi River, saw record rainfall in April that recharged soils depleted of moisture following last summer’s worst drought since 1934. But cooler-than-normal temperatures left fields too wet for planting and also slowed crop emergence in planted fields.
“The new stuff going in now, it will be up in a week or 10 days,” said Roger Elmore, extension agronomist at Iowa State University in the country’s top corn producing state. “It will be very competitive and probably be higher yielding than the stuff that was put in earlier.”
However, farmers risk yield loss if they plant in fields that are not fully dry. Soils can become compacted, slowing root growth.
“People are going to be pushing soil conditions more than they should just to get things done quickly,” Elmore said. “If a lot of guys are mudding it in, that’ll reduce yield.”
Farmers in southern Indiana are eager to begin seeding corn to put last summer’s devastating drought behind them, but many have been sidelined for weeks as on-and-off rains have kept their fields too soggy for heavy planting machinery, industry sources said.
Producers there are not yet switching their corn acres to soybeans, which can be planted later in the spring, as this week’s window of warm, clear weather was expected to remain open until Thursday. But another rain system was expected to arrive late this week.
“They’re calling for another half inch or inch of rain later this week so, if they don’t get corn in by Thursday, I‘m sure some guys will be seriously thinking about switching,” a dealer at a southern Indiana elevator said. (Additional reporting by Tom Polansek in Chicago; Editing by Peter Galloway)