High daytime temps not a big concern in corn
The spike of above-average daytime temperatures throughout much of Illinois during the third week of July should not raise concerns for the corn crop as most areas had enough water in the soil to carry crops through that week, said University of Illinois professor of crop sciences Emerson Nafziger.
However, higher than normal night temperatures during the past week might have hurt pollination success in areas where soils are starting to dry out, Nafziger said.
“The heavy silking that preceded the full emergence of tassels, as noted in recent years, is very much evidenced again this year. This means there should be little concern about having silks present when pollen is being shed,” he said.
Nafziger said that 21 percent of the Illinois corn crop was pollinating on July 14, and this moved to 64 percent by July 21. “Planting was concentrated in the third week of May this year, so pollination is also occurring relatively quickly. That’s a week or so later than normal,” he added.
In some fields planted in mid-May or later, especially those planted at high populations, stalk diameter is noticeably smaller than often seen in earlier-planted corn. Later-planted corn with adequate soil moisture often grows taller than early-planted corn because of higher temperatures during internode elongation. Because late planting doesn’t increase plant weight, stalks end up tall and on the thin side, Nafziger said.
“Plants with smaller stalks often have less leaf area, and thus less ability to set and fill a large ear. It’s too early to know if this will decrease yield potential, but it is one of the ways in which late planting can lead to lower yields,” he said.
A return to better soil moisture conditions along with lower night temperatures over the next two weeks should allow good kernel set. After a wet June, Nafziger said soil moisture is becoming a concern in some places. July rainfall has been less than normal over much of Illinois, with less than an inch so far in parts of western and northern Illinois.
“The soil water supply was good coming into July, but how well the crop is tapping into this supply will make a difference as we move into the second half of the season,” Nafziger said. “Fields that were planted have had a chance to produce a good crop canopy, which in turn enabled deeper root growth. Roots may not be as extensive as they were in July 2012, but as we saw last year, good root systems don’t help when there’s no available water in the soil.”