Harvesting High-Moisture Corn
The cool weather in June plus the unusually cool weather in August has placed corn maturity behind schedule, says a North Dakota State University agricultural engineer. “The cool weather has slowed corn maturity to the point that a normal frost date will likely produce a considerable amount of immature corn,” says Vern Hofman of the NDSU Extension Service. “An early frost would increase the problem.”
Frost damage before physiological maturity will affect corn in a number of ways. It will reduce yields, increase dockage due to harvest damage, lower test weight, reduce harvest efficiency due to wetter-than-normal corn and increase drying costs.
During corn harvest, wet kernels will be harder to thresh from wetter-than-normal cobs. The tougher shelling will cause more damage to the kernels and more broken cobs. Wet kernels will also increase the load on the combine cleaning sieves.
To improve shelling efficiency when the kernel moisture content is above 30 percent, cylinder or rotor speeds above those recommended by the manufacturers will be needed. However, excessive threshing RPMs is the main cause of kernel damage and cob breakup, which can lead to poor separation on the combine cleaning shoe. “Producers should keep cylinder or rotor speeds as low as possible to get the threshing done,” Hofman says. “Producers should narrow the concave spacing to increase threshing capability and then increase cylinder or rotor speed as a last resort. As the crop dries during the harvest season, reduce the cylinder speed as much as possible. When the cylinder speed has been reduced to the normal range, widen the concave spacing as much as possible.”
Corn harvesting during unusual circumstances will also require an awareness of corn head adjustments. Immature corn may have smaller ears and stalks. To prevent ear loss and excessive shelling at the header, both the snapping rollers and stripper plates will need to be closer together to compensate for the smaller ears. The spacing between the stripper plates should be slightly wider at the back, usually by 1/8 to 1/4 inch. This helps move stalks between the snapping rollers while minimizing the amount of foreign material going through the combine.
Corn producers should also maintain the correct gathering chain and snapping roller speed. Attempting to speed up because of low yields or slow down due to lodged corn should not be done without an appropriate speed change to the corn head drive shaft.
“Producers may also want to consider harvesting a corn cob mix silage if a buyer can be found,” Hofman says. “This would allow for greater hauling distances as compared to whole plant silage. The combine could be used with a high cylinder speed to break up the ears and crack the corn kernels. Usually combine manufacturers have these recommendations in their operator’s manual. The sieves need to be removed from the combine to allow for the flow of large cob pieces through the machine. This would also knock down the stalks so less snow would accumulate in the field next winter. A disc type no-till drill could then be used for seeding next spring.”
If corn is immature after the first hard frost, a producer should consider chopping the crop for silage. “For good silage, the corn must be chopped at the correct moisture content,” Hofman says. “Corn that is too wet or dry will not make good silage. In those parts of the state with a large corn acreage, low cattle numbers or long hauling distances, chopping for silage may not be economical. If a corn crop is so immature that it isn’t worth running through a combine and silage is not an option, the field may best be worked down.”
Corn stalks can be chopped with a stalk chopper, but producers should wait until the stalks dry down. Producers will be able to use a hoe-type air seeder without additional soil preparation if they chop the stalks and allow them to overwinter. If a producer uses a disc-type no-till drill, leaving the stalks upright may be the best option. Growers should consider the extra snow standing stalks may collect. Extra snow may delay planting next spring.
Using a heavy tandem disc is another method for destroying stalks. It will cause soil disturbance and bury some stalks, but will still provide some soil cover to prevent erosion.
“Producers must also consider the fertilizer value of the crop that is being destroyed,” Hofman says. “It should not be considered a total loss, due to the soil fertility value. It will be difficult to determine the fertilizer value of a corn crop that has been incorporated into the soil until it decomposes, but a good portion of the decomposed residue will be available for next year’s crop. Soil testing this fall or next spring will not give an indication of the crops’ fertilizer value.
“Chopping stalks or working a crop down is a last resort, but producers need to consider the cost of combining, drying and storage and the low value of a possible poor crop. A corn crop with low test weight is going to have little value except for livestock feed, and if a grower considers the cost of harvesting and drying, destroying a crop may be the best alternative,” he says.