Editor’s note: The following was written by Kris Kohl, Iowa State University Extension ag engineering specialist, for the Clippings Extension newsletter. The crop will soon be coming out of the field, and with the very late replant and the overall early planting of the rest of the fields, the difference between moisture content will be very wide. Also, the low crop prices have many farmers planning to store the corn and soybeans longer than in the past.
When grain is more than four moisture points different, it tends to separate in the storage pile because of flow and friction and accumulates in spots like the center of a bin, with the broken kernels plugging the air paths. Because wet grain has all the needed nutrients for bacteria to grow and their byproducts are heat and moisture from the destruction of the grain, a chain reaction can start. A wet spot as small as a basketball can spoil the whole bin regardless of size.
Moisture testers do a very good job of testing grain that is uniform in moisture. When the kernels are different, it will tend to read higher than the average because the electrical conductivity of the wetter kernels are going to be overrepresented. Hand shelling a sample for testing will often read three to four points dryer because the combine will tip many of the wetter kernels.
The tip is the last place to dry. The butt end of an ear is wetter than the tip, and second ears on a stalk are often 10 points wetter than the main ear. When hand shelling, try to go to some of the replant areas, take second ears and don’t just grab the best ears near the edge of the field.
In a corn bin, the edge of the bin often has dryer corn than the center, so take your samples there so you don’t get a false dryer reading. Here’s a short story about how one large wet soybean changed the reading of a whole sample: A farmer tested a sample of soybeans and got a reading of 18%. Thinking it was too high, he dumped it into a shallow pan to look at it.
There was one big green bean in the sample that was not mature, so he removed it and put it back into the tester and the sample then read 14%. This year the early-planted corn will mature early and may be harvestable before the soybeans when the low temperatures are above 50. While it is tempting to go through replant areas so that the field is done, the wet corn and fines will accumulate in the center, plugging the pathway for air and could start a spoiling time-bomb.
Start with the best fields and core the bins four times during filling rather than the two times that are the standard recommendation. Look closely at this cored grain as it tends to be the lower quality that will give you more problems. Turn the cooling fans on and try to get the grain below 40 degrees.
If overnight lows are not that cool, then you may need to come back in a week or two to finish the job. Many farmers have gotten used to no drying charges for 18% corn going to the ethanol plants and have managed the corn to meet this new standard. There has always been a risk of it going out of condition, but harvested cold and sold by March has worked in the past.
If we plan to go through the summer and store it longer than one year, we must start with corn at 14% or dryer and cooled below 40 degrees as quick as possible. The cost of drying it and the loss in weight need to be understood, but spoiled corn is a nightmare no one ever wants to experience..
