Last week I received several calls from dairy producers requesting information on pricing corn purchased from neighboring crop producers and stored as high moisture ear corn. I discovered that figuring the total weight of a bushel of ear corn at various moisture contents is not as easy as simply computing the amount of dry matter in a bushel of dry ear corn and then adjusting the moisture content as you can with shelled corn.
I have purchased high moisture shelled corn from neighbors at harvest several times and used the following procedure to price it:
Corn price is based on No. 2 corn, weighing 56 pounds per bushel at 15.5 percent moisture. That’s 47.58 pounds of dry matter (56 x .845) per bushel.
I assume that the water has no value and that you want to convert the corn to an equivalent weight of No. 2 corn and then use the current price of No. 2 corn. If the corn has 25 percent moisture, I would divide the weight of dry matter per bushel by the decimal that equals the percent dry matter of the wet corn to get the weight per bushel of the wet corn.
So, 25 percent moisture corn would weigh (47.58/.72) = 63.09 pounds per bushel.
Do not use an elevator shrinkage chart for this calculation, because such charts show the reduction in dry weight due to handling and drying, most of which will not occur with high moisture corn.
Ear corn different
The equivalent amount of dry matter in No. 2 shelled corn in the form of ear corn weighs 68.4 pounds (see the accompanying chart from Iowa State University). That’s 57.8 pounds (68.4 x .845) of dry matter.
But, if you try to do the same calculation to find the weight of ear corn at a specific moisture content, it doesn’t work. The ratio of moisture contents of kernels and cobs in a bushel of ear corn varies considerably.
Values in charts showing weights of ear corn and shelled corn at specific moisture contents are based on averages of many varieties over different years. Since the cobs dry down more slowly than the kernels, the ratio of kernel dry weight to total bushel weight changes as drying proceeds.
You will have to simply go to a chart like this one and get a weight per bushel for ear corn at the average kernel moisture of the corn you are buying.
What about the cobs?
Keep in mind that many growers harvest high moisture corn with a combine and try to save all the cobs with the corn. However, some of the cob usually is lost in these situations, so you will have to adjust these calculations to account for that loss of cobs.
Estimate the percentage of cobs being saved and adjust the weight of the cobs. Calculate the weight of the cobs by subtracting the weight of an equivalent amount of wet shelled corn at the same moisture content, adjust the cob weight and then add the cobs back to the wet shelled corn to get the weight of a bushel of ear corn with only part of the cobs included.
Let’s say you estimate that 30 percent of the cobs are going on the ground and that the kernel moisture content of the ear corn is 25 percent.
A bushel of ear corn at 25 percent moisture weighs 81.25 pounds From the shelled corn column, we see that shelled corn at 25 percent moisture weighs 63.45 pounds per bushel. So, there must be (81.25 – 63.45) = 17.8 pounds of wet cobs in a bushel of 25 percent moisture ear corn.
If 30 percent of the cobs are going on the ground, then 70 percent (17.8 x .70) = 12.46 pounds of cobs are going in the bin. So, each bushel of wet shelled corn in the bin is accompanied by 12.46 pounds of wet cobs, for a total weight of (63.45 + 12.46) = 75.91 pounds.
Divide the total weight of ear corn at 25 percent moisture by 75.91 pounds per bushel to get the equivalent number of bushels of No. 2 corn.
Using this method, a ton of high moisture ear corn containing 70 percent of the cobs and 25 percent moisture would contain (2,000 pounds/75.91) = 26.35 bushels of No. 2 corn equivalent.
If you use the No. 2 shelled corn price, you are assuming there is no value to the cobs. Obviously, the cobs have great value to you as a dairy producer, but are not worth much to the cash corn producer. You may want to compensate the corn grower for the additional fertilizer nutrients removed in the form of cobs.
This should give you a place to start from in negotiating a fair price for the grain.
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