Corn planted later in the season isn’t mature at the same time as what was planted on time—duh, right? It’s more than just the calendar delaying the corn’s maturity, something is making it take more growing degree days (GDDs) than even the maturity rating indicates.
Bob Nielsen at Purdue University is trying to figure out this bizarre phenomenon. While it might not save this year’s crop, it’s a learning opportunity for the future.
“The big question is why are these late-planted fields maturing in more GDD than our earlier research predicted?” Nielsen asked in a recent report. “The answer is not clear, but there is some evidence that kernel black layer development occurs in response to reduced sucrose availability late in the season as photosynthesis slows in response to general late-season leaf deterioration and/or sub-optimum cooler temperatures.”
Cool temperatures typical for September and October, but before a killing frost, tell the crop it’s time to mature. This year, higher-than-normal September temperatures might have changed the plant’s sucrose balance and delayed black layer.
“September 2019 was 4 degrees to 7 degrees Fahrenheit warmer than normal in Indiana,” Nielsen said. “The positive impact of those warm temperatures on GDD accumulations during September was dramatic. That fact, plus the possible relationship between late-season sucrose availability and kernel black layer development may explain why some late-planted corn fields are maturing later than expected both in terms of GDD and calendar date.”
In his research, none of the hybrids in trials reached black layer by mid-to late-September as predicted by late planting adjusted GDDs.
What does this mean for next year? Hybrid maturity might be more influenced by weather than originally assumed, but not necessarily early-season weather. Late season weather outside of the norm, with different crop maturity seems to have a prolonged effect on the crop.