After farmers harvest their corn, soybeans and other crops from the field they sometimes have to dry the grain. But, why do they do that?
Grain is sold by weight. You might have heard the agriculture report on the radio and they talk about corn prices being 350 or read the markets page in the newspaper and they list soybean prices at 867. What that means is that corn is selling for $3.50 per bushel and that soybeans are selling at $8.67 per bushel. A bushel is a unit of measure for the weight of that grain. A bushel of corn weighs 56 pounds. A bushel of soybeans weighs 60 pounds. Other grains have different weights for a bushel. In terms of volume, think of a small laundry basket as being one bushel.
When corn is mature in the field it has approximately 30% moisture (water). Farmers let corn dry in the field for as long as possible and will ideally harvest when the moisture level is 23 to 25% or lower. At this moisture level, kernels shell easily and stalks generally stand better making harvest more efficient.
Ideal moisture for harvesting soybeans is 13-15%. If the moisture level is higher than 18%, the soybeans can be crushed or bruised too easily. If the moisture level is lower than 10%, the seeds become brittle and might split during harvest and handling.
You may remember from science class that water weighs a lot (8.34 pounds per gallon!). So that means that the more water that is inside the grain, the more it will weigh. A long time ago they decided that grain needed to be uniform in water content so that when they weigh it to be sold they could fairly determine prices. When a farmer brings their grain to the elevator or cooperative to be sold, they will stick a probe into the grain to determine the moisture content. If the moisture in the grain is too high when it is sold, the farmer would not receive as good a price. For example, soybeans might be discounted up to $0.12 for every percentage point of moisture over 13%.
It is hard to harvest corn or soybeans when they are at exactly the right level of moisture. If the crop is left out in the field and Mother Nature decides to rain a lot in the fall, the crop may never dry enough. Most farmers have access to grain dryers either on their farm or at local cooperatives. By putting the corn or soybeans through these grain dryers they can dry the grain to the desired moisture level.
Farmers also dry grain for another reason. Sometimes grain is stored for several months after harvest but before it is sold or used. Grain is placed into large storage bins. Grain like any plant or food has the potential to spoil. If the grain has a high moisture content when it is put into the bin it might develop a mold resulting in crop loss. (Think about how quickly moist soft bread might turn moldy on your counter top and how a dry saltine cracker won’t turn moldy.) If they are storing corn, farmers try to prevent this mold and crop loss by drying the corn to less than 15%.
There are lots of different types of grain dryers. They are kind of like the clothes dryer that you might use when you do laundry. Many grain dryers use propane or natural gas to heat air and then use large fans to push the air through the grain.
Other grain dryers may use augers to move the grain through the bin to maximize efficiency and try to dry the grain uniformly.
While most grain dryers do use propane or electricity to create a heat source, some farmers are experimenting with thermal grain dryers that are heated solely with the sun. This process can take more time but is very cost efficient with the right set up.
Ultimately, farmers dry grain to prevent any loss of their crop and to ensure they get the best price for their crop. If we don’t have a nice dry fall, then it’s time to turn to technology and innovation to solve the problem of too much moisture in our corn and soybeans!