By Dan Martens
University of Minnesota Extension
Ken Hellevang, North Dakota State University grain handling specialist, wrote recently about issues and strategies to consider with the 2014 corn harvest. These issues are relevant in our area.
Check field conditions and consider harvesting early to minimize losses even though areas of the field may be at higher moisture contents. Drought conditions stress the corn crop, leading to weak stalks and shanks. Weak stalks contribute to “downed” corn due to wind or other forces, and weak shanks contribute to “ear drop” and large field losses. Drought conditions also lead to larger than normal in-field corn moisture content variations. Moisture content might range from 15 to 25 percent in the same field due to soil variations and other factors.
I’d add that there might be places where combining drier areas of the fields separately might be an advantage for drying and storing crop with more uniform conditions. Some combine heads do a surprisingly good job of cutting across rows if speed is reduced a notch. A little harvest loss in carving out pieces of fields might be less than the loss experienced in waiting for wetter parts of fields to dry.
Kernel moisture content, size and density or test weight likely will vary on an individual cob as well. Drought stress leads to small kernels on part of the cob and large kernels on other parts of the cob. Even the larger kernels may have a lower test weight due to the plant stress.
Watch combine settings. Corn moisture variation in a field means that adjusting the combine for conditions will be difficult, and that may contribute to more fines in the corn. Cylinder and concave clearance, cylinder speed, fan speed, chaffer and sieve openings should be considered.
Consider screen cleaner before binning to remove fines, cob pieces and broken kernels. More fines are produced when corn is wet because more aggressive shelling is required. This causes more kernel cracking and breaking. Immature corn contains more small and shriveled kernels. Fines cause storage problems because they spoil faster than whole kernels, have high airflow resistance and accumulate in high concentrations under the fill hole unless a spreader or distributor is used.
Field Drying Rates, of course, depend on weather conditions. Corn in the field might dry 1.5 to 3 percentage points per week during October and 1 to 1.5 or less per week during November, assuming normal North Dakota weather conditions. If corn has a moisture content of 35 percent on Oct. 1, it might dry to about 25 percent moisture by Nov. 1. (This probably is not a lot different for our area of Minnesota.) Field drying normally is more economical until mid-October, and mechanical high-temperature drying normally is more economical after that.
If the moisture content varies in corn going into a high-temperature dryer, it also will vary coming out of the dryer, Hellevang says. For example, if the moisture ranges from 15 to 25 percent going into the dryer, it may range from 11 to 19 percent coming out. More mixing in the dryer will help reduce the moisture variation coming from the dryer. This moisture variation will greatly affect storability and storage management.
Run aeration fans to help move moisture from wet to drier kernels. Air going past wet kernels picks up moisture, and that moisture will transfer to drier kernels as the air goes past them. Moisture movement will be minimal without aeration airflow past the kernels. Run the fan longer than is required to cool the grain to even out the moisture content. The moisture may not equalize, but will become more uniform. Moisture content still may range from 14 to more than 16 percent.
Use a distributor or “coring” of the bin to reduce the accumulation of smaller material in the center of the bin. Grain segregates based on size and density as it flows into a bin or container. Generally, the smaller and denser material will accumulate in the center and the larger material flows to the perimeter of the bin. Therefore, areas of wet corn and variations in test weight are possible in a bin.
“Coring” means taking corn from the bottom center of a bin. Livestock farmers do this by feeding out of the bin. Cash crop producers might do this by selling or moving a load.
Please make SAFETY a PRIORITY through the harvest season. Stay out of trucks, wagons and bins where grain is moving.