With the cooler temperatures that we have been experiencing, many farmers are wondering if that may mean an early frost is likely this year, and if that might impact yields. Iowa State University Extension Crops Specialist, Joel DeJong, works in northwest Iowa and says most of the corn he has seen is in what’s called the “dough stage.”

“That leaves us about 40 days from maturity, so that gets us to maturity with fairly normal conditions between now and the end of September near about the 25th of September,” Dejong says. He says different hybrids will have different maturity dates, but most should be mature by the end of September.

DeJong says if temperatures remain cooler than normal for a significant time period, that could further slow down the maturity development process. He says the closer to the maturity date before frost hits, the less likelihood for yield loss. “That last week before we hit maturity, we don’t lose much yield, it’s if we get hit three weeks before maturity that it is much worse,” Dejong says. He says the gives him a lot of optimism and he says when the kernels of the corn are filling slowly like they have been that’s usually when you get some of the best yields.

The crops specialist says the corn has lost some of the warmth it needs to grow. He says the low temperatures are typically in the 60s and we have been around 10 degrees below that. The highs have been close to normal, but he says the cooler weather has led to giving up about five growing-degree units per day, “About 20 or 25 units is about the equivalent of a day, so we gave up another day’s worth of growing units again this week,”Dejong says.

The U.S.D.A. crop report out Monday showed over half of Iowa’s corn acreage was in that key dough stage, which is more than two weeks ahead of 2013 and a week ahead of the five-year average.

By Dennis Morrice, KLEM, Le Mars