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Wet corn harvesting challenges

STEVE JOHNSON 09/19/2013 @ 8:11am Farm Management Specialist with ISU Extension housed in Polk County, Iowa. Areas of expertise include crop marketing, grain contracts, government farm programs, crop insurance, farmland leasing and other crop risk management strategies. Reach Steve by e-mail at sdjohns@iastate.edu.

While half of Iowa’s corn crop was planted by mid-May, much was pushed back several weeks. Some fields were replanted more than once and, as a result, pollinated into August.

The bottom line for many growers is that corn maturity has been delayed. The problem with harvest may be a wetter-than-normal crop created by a combination of late planting and then impacted by hot, dry conditions during grain fill.

Iowa farmers are now expected to harvest about 13.5 million acres of corn; that’s 200,000 acres less than last year’s drought-ravaged crop. The latest USDA estimate is that Iowa would average 162 bushels per acre, below the 30-year state trend yield by 17 bushels. The variability of corn yields and moisture levels is going to be large across the state. Much depends on the corn planting date and the water-holding capacity of the soils.

Some corn plants that died prematurely may already be harvested, but much of Iowa’s crop will be slow to dry down in the field. It will need to be harvested and dried down to near 14% or 15% moisture to avoid a discount or extended storage time for bushels to be marketed later. Delivery of wet corn sold will carry moisture discount at roughly 2% times the points of moisture above 15% times the cash contract price.

For corn harvested at 25% moisture and averaging 170 bushels per acre dry, that’s about $90 per acre with corn valued at $4.50 per bushel. This amount roughly equals the cost of commercial drying charges using a 1.4% shrink factor and 4.75 cents per point of moisture. Drying and storage of corn may be a problem as harvest gets underway.

Heavy drying needs

The key thing for a grower is to think ahead about corn moisture levels, drying, and storage costs. Be prepared. There’s an abundant supply of propane out there. The challenge this fall — if harvested grain needs a lot of drying — will be having the propane in the right place at the right time.

Perhaps the most important factor in dealing with corn at higher moisture levels at harvest is getting the combine set up right. Some things to remember are:

  • A properly adjusted combine can handle corn between 20% and 30% moisture, but expect grain damage to increase unless careful attention is paid to combine settings.

  • Be sure to select a ground speed adequate to keep the separator and cleaning shoe at full speed. Adjust your hydrostatic transmission to maintain the engine near rated speed under varying crop conditions.

  • Operate the corn head as high as possible to reduce getting wet plant material in the combine, which can significantly reduce the machine’s ability to thresh and separate the grain.

  • Before changing concave clearance, make sure it is level side-to-side in a conventional combine or front-to-back in a rotary combine so that the adjustment is uniform.

While corn harvest may begin later than normal this fall, farmers will want to be prepared early.

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