Sunday’s forecast from the National Weather Service eased up on the corn cooking temperatures, and added some chance of precipitation, at least enough for the Sunday night futures market to head downward instead of upward. However, oven-like temperatures will be curling corn leaves, interrupting pollination and aborting some tip kernels for the next few days. Let’s get to the details.
With the weather maps showing red temperatures, there is not much chance for precipitation, despite the fact corn needs three to four tenths of an inch of water per day during pollination. Pollen and silks are predominantly water, and Iowa State corn specialist Roger Elmore says both moisture and temperatures are important. He’s particularly concerned about the relatively high overnight temperatures, because cool mornings are what triggers pollen shed. Over this week and next an estimated 85% of the US corn crop will be pollinating.
The National Weather Service forecast issued Sunday calls for Cornbelt temperatures to be above normals. The Climate Prediction Center says, “Temperatures are likely to be in the warmest one-third of all years in the eastern three-fourths of the 48 states and very likely to be in the warmest one-third in the eastern Cornbelt.” IA St. meteorologist Elwynn Taylor says, “This type of temperature cycling is typical of strong La Niña conditions and may be the last extreme cycle as the La Niña event diminished to neutral conditions July 1.
So is this a parallel of 1988? Elwynn Taylor says, no, because the drought began earlier in the growing season in 1988. But he’s still concerned about the balance of the growing season, “A point of concern is the forecast distribution of the warm temperatures: warmer than usual in the East and cooler than usual in the West with the transition approximately at the Continental Divide. Such distributions tend to persist for up to six weeks and consistently result in below trend corn yield for the U.S. as was the case in 2010.”
When there is a lack of moisture, but an abundance of heat, what happens to the corn plant? Roger Elmore at Iowa State says there are two impacts, 1) Corn with rolled leaves will lose 1% of yield every 12 hours, except when pollinating, when yield is cut 1% every 4 hours of leaf rolling, 2) an additional 1% yield loss per day if leaves remain rolled for 4 consecutive days, on the sixth day of rolled leaves that yield loss climbs to 4% per day.