The weather may continue to cause great angst for farmers as a potential frost looms, ending the growing season for some fields where grain was not yet mature.

The weather wasn’t kind to many farmers this spring, with too much rain significantly delaying planting. Most acres were planted after the first week of June. So, a frost mid-October on unmatured crops will further cut into yield potential and farmers’ profits.

“We still have a number of corn acres not at full maturity,” says Jim Zook, executive director of the Corn Marketing Program of Michigan. “With a killing frost, the corn crop won’t naturally dry down. When it doesn’t, it will be harder to dry and store long term. Worse yet, what we’ve seen before, when you do get some snow or other rains, the corn crop may actually pick up moisture.”

The caveat is whether farmers planted shorter-maturity varieties, he adds.

Most of Michigan’s soybeans are now in the R7 and R8 growth stages, according to Mark Seamon, research coordinator for the Michigan Soybean Promotion Committee. “R7 begins when one pod on the plant reaches a fully mature color,” he says. “I believe that this represents the most acres of soybeans throughout the state. These beans would ideally like 10 to 15 days of good weather before harvest, but are mostly safe from significant frost damage. The R8 fields are very near harvest (zero to seven days from harvest). A few late-planted fields are not quite as mature and could be hurt by frost. 

“If the low temperature does not get extreme and/or last for many hours, the damage should be limited to the tops of the plants. A few pods could be affected that may cause the beans in them to die and not change color to yellow as they normally would.”

A large amount of the concern for frost damage to soybeans in Michigan has passed in the last days of September and first week of October, he says. “The fields that have significant green color may be an exception to that and should be harvested and managed separately from other normal fields,” Seamon advises.

Temps of concern

Plants are killed when temperatures are near 32 degrees F for a few hours, or when temperatures are near 28 degrees for a few minutes, according to Ned Birkey, Michigan State University Extension educator. At temperatures between 32 and 40 degrees, damage may be quite variable and strongly influenced by small variation in microclimates of slope, terrain, air movement, air drainage and thermal radiation, creating small frost pockets, he says. 

Maturity in corn occurs when kernels form a black layer at the kernel tip and grain will be at approximately 30% to 35% moisture. Birkey says differences among hybrids, overall plant vigor at the time of frost and subsequent temperatures will all affect final grain quality.

He advises farmers to closely monitor stalk quality or rot to partly determine a harvest strategy.

Storage plans

Zook says corn growers need to make sure they take the time to get this crop dried down — further than normal. “Storability is going to be challenging, so special care is needed beforehand.”

He couldn’t estimate a loss per bushel, but if a killing frost hits immature fields, “expect a 5% to 10% cut because of low test weights, on top of weaker corn yields,” he says.

According to Purdue University, yield loss due to frost or freeze injury to immature healthy corn depends on the stage of kernel development when the frost or freeze occurred, and the severity of the injury to the plants.

Estimates of potential yield loss due to frost or freeze injury:

Certain areas of the state are further behind in maturity than others, including the center part of state. “The counites of Clinton, Washtenaw, Lenawee, some of Ingham, southern Hillsdale and, basically, south M-46 into the Thumb,” Zook says. “That includes parts of Tuscola, Lapeer and Sanilac. Monroe had a lot that just didn’t get planted, but what did, should be OK.”

USDA says the state’s corn crop condition is 44% good-to-excellent, with 82% dented and 31%  mature. Corn silage harvest is 42% complete and grain harvest is at 4%.

Soybeans are 69% dropping leaves, 8% harvested, and condition is 41% good-to=excellent. 

If soybeans are killed prematurely, Seamon says, they may not make their full size, color or quality, which can lead to an increased amount of foreign matter in grain samples. “If they are  excessively green color, they may be discounted by some buyers,” he says. “Fields with frost-damaged soybeans should be isolated from others, as storage management may need to be adjusted.”

Typical frost date

Michigan’s 10-year average for first frost date is around Oct. 22 and about a week later for areas around the lakes.

If Michigan can dodge a frost in the next few days, both Jeff Andresen, the state climatologist, and Jim Noel with the National Weather Service Ohio River Forecast Center, agree that the first half of October may see more seasonal temperatures. Then the pattern is expected to return to above-normal temperatures and precipitation for the second half of October. Both meteorologists are also forecasting November to be warmer than normal, with precipitation near to above normal. 

During the Between the Rows Tour of the state in late August, Zook and his staff conducted 380 yield checks. “The crop looks fairly decent for being planted so late. We estimate 152 bushels per acre, which is better than what we expected — and what USDA forecasts.”

For soybeans, many experts have suggested that the state average yield for soybeans will be near 40 bushels per acre. “We hope that we will be pleasantly surprised, but some early harvest indications are not showing high yields compared to other years in the same field,” Seamon says.