USDA’s Monday afternoon crop progress report indicated 5% of US corn had been harvested compared to 20% last year and 14% for the five year average. Additionally, only 33% of the US corn crop was mature as of Sept. 21, compared to 76% last year and 63% for the five year average. While the crop is still laboring to get to the black layer point of maturity, frost threats are being made for the upper reaches of the Cornbelt where corn maturity is only in the teens in North Dakota, Minnesota, and Wisconsin. That will force many farmers to push harvest faster than they would like, and that means extra headaches in harvesting and storing an immature and wet crop.

For some farmers the only choice will be silage. In the northern tier of the Cornbelt substantial acreage has yet to dent; and Ken Hellevang, ag engineer at North Dakota State University says, “Yield potential for corn frozen during the milk stage is low. Ears are difficult to pick and shell, kernel tips may stay on the cobs and grain will be very chaffy.” And he adds, green chopping and ensiling may be the only reasonable options. Hellevang’s Tips for Harvesting Late-Maturing Corn offers numerous checklist items for farmers whose late corn is still green in the wake of cold temperatures.

Silage:
• Harvest at 60% to 70% moisture with cut length about one-half inch.
• Store in a bunker or horizontal silo with a crowned center and slope of 1:6 or 1:8 and covered with 6 mil. plastic. If the temperature reaches 120 degrees after four days, too much air is getting under the plastic.

Field drying:
• If corn is frozen in the dough stage, test weights will be in the 40 lb. range, and although it will eventually dry, Hellevang says field drying will take an additional week.
• Frozen wet corn is more susceptible to molds if the frost is followed by warm weather, and mold growth will only stop with ensiling the corn or drying it in a bin.
• Even a warm day with a breeze will not take out more than three-quarters of a point of moisture from mature corn per day. As temperatures cool, drying rates slow.

High moisture corn:
• If using silos or bags where outside air is excluded, corn should be 25% to 30% moisture, and any air gaps should be sealed to prevent storage loss.
• If wet grain is placed in silos, it will exert more pressure on the walls, so additional support will be needed, and the silo must not be completely filled.

Bin drying:
• Natural drying in the field should be allowed for as long as possible, but as weather gets colder and drying rates diminish, then field losses will increase.
• Corn over 21% moisture should not be dried with only natural air and low temperature to minimize spoilage. Hellevang recommends adding heat to reduce the moisture content and an airflow rate of 1.25 cubic feet per minute per bushel to reduce drying time.
• Shelled corn can be stored up to 25% moisture if aeration is used and temperatures are below 30 degrees.
• Grain dryers will be used long and hard and should be in good working condition before turning them on for the first time.
• The maximum allowable drying temperature should be used to increase its capacity and attain energy efficiency. High temperature drying will reduce test weight and increase susceptibility for breakage.

Dryeration:
• Dryeration will increase dryer capacity by 50% to 75%, reduce energy use by 25%, and can remove 2% or more moisture.
• Dryeration requires close monitoring, and is labor intensive with required transfers from bin to bin.

Drying costs
• Save on energy costs and corn quality by using the maximum drying temperature of 200 degrees, which will remove water with less energy than lower temperature.
• At $2 propane, you will spend about $53 to remove 10 percentage points of moisture from 120 bushels of corn.
• For corn at 56 pound test weight, drying it from 25% to 15% moisture will remove 7.5 pounds of water.

Moisture measurement
• Shrink is a factor that will need to be calculated, and is a 1.1834 % in weight decrease for each percent of moisture removed.
• Moisture meters will not provide a good reading on corn coming from a high temperature dryer because of the heat and may give a readying 2% lower than true.
• To get a true moisture reading, cool the sample to room temperature before taking the reading.
• Corn test weight rises about one-quarter pound for each point of moisture removed during high temperature drying, but there will be little increase on immature or frost damaged corn.

Kernel damage
• With aggressive shelling, more fines will be produced from kernel cracking and the presence of immature corn.
• Fines will spoil faster and cause more storage problems, particularly as they pile up in the center core of a bin.

Summary:
The potential for a late harvest because of immature corn will create harvest, drying, and storage problems for many farmers. Because there has been favorable fall weather the past several years, refresh yourself on combine settings for high moisture corn, along with extra preparation for having to dry a large crop. Kernels may be damaged in the process, and extra expense will be incurred because of the additional energy needs.