Imbibitional Chilling Concern Throughout Midwest
Corn planting is under way throughout much of the Midwest. The weekly USDA Weekly Crop Progress Report showed the 2017 corn planting pace behind average at 17%.
The pace may fall further behind average with the forecast calling for above-normal rainfall and below-normal temperatures over the next 10 days or so (through the first week of May), says Emerson Nafziger, University of Illinois Extension agronomist.
“Above-normal growing degree day (GDD) accumulations have meant fast emergence for corn,” says Nafziger. “In central and southern Illinois, corn planted by April 19 accumulated, by April 25 or 26, the 115 or so GDD required to emerge. With lower temperatures expected over the next 10 days, corn planted on April 25 or 26 may take almost twice as many days to emerge as corn planted in mid-April.”
The forecast is similar for much of the rest of the Midwest. “There is a big rain event predicted for parts of Missouri, Arkansas, Oklahoma, and southern Illinois,” says Al Kluis, Kluis Commodities. “Some predictions call for up to 10 inches of rain.”
In Iowa, much of the state soil temperatures have reached 50°F., but soil temperatures could drop with the cold weather, says Mark Licht, Iowa State Extension cropping systems specialist.
“This is of concern because the impact from imbibitional chilling could have a big impact on corn yield potential,” says Licht. “Imbibition is the process by which seeds absorb water to initiate germination. The critical time period is 24 to 36 hours after planting.”
Imbibitional chilling injury can happen when the water available to the corn seed has a temperature in the lower 40s or less, says Nafziger. “Uptake of cold water damages membranes, and this in turn may cause abnormal seedling development and failure to emerge.”
Is your corn at risk?
“If the corn seed can take up some warmer water before soil (and water) temperatures drop, we often see less injury or none at all,” says Nafziger.
Corn planted early this week should be out of danger. “Corn planted on April 25 or 26 may be at risk, but rain that fell on April 26 (in Illinois) was not very cold, and with air temperatures expected to rebound into the 70s the last two days of April, along with the (warmer) rain that’s predicted, we hope not to see much of this problem from this round of weather,” explains Nafziger.
Saturated soils will be another concern for many the next few days.
“Seeds that are starting to germinate need oxygen, and will usually not survive the low oxygen levels in saturated soils for more than a couple of days,” says Nafziger. “They will survive longer if soil temperatures are cool, both because that slows growth and lowers oxygen demand, and also because cool water carries more oxygen into the soil. If soils start to dry off early next week, survival will be a concern mostly where water stands.”
Young seedlings have the advantage of having roots that might find pockets with more oxygen, but they still depend on seed reserves to grow, especially if it’s cool and cloudy, and before leaves have much green area, says Nafziger. “These reserves are mostly used up by the time the plant has two leaves, and diseases can invade the endosperm, especially in cool, wet soils.”
Seedlings can be expected to live for three to four days if they are submerged, and a few days longer than that if only the roots are in saturated soil. If plants remain alive, chances for seedlings to revive and thrive increase considerably once oxygen gets to the roots again.
“If the weather remains cool, emergence and growth will be quite slow even if it does eventually dry up enough to resume planting,” says Nafziger. “So warmer temperatures will help both to dry things out and to get the planted crop growing.”