Test weight of corn determines the weight of a bushel volume (1.244 cubic feet) of grain. Test weights determined on dry (15.5 percent moisture) corn can indicate whether the grain crop reached full maturity. Low test weights indicate immaturity. The minimum test weight for USDA No. 2 corn is 54 pounds per bushel. Test weights of wet corn are lower than those of corn that has been dried to 15.5 percent. In other words, as corn grain dries, test weight increases slightly.
For many classes of livestock, the feed value of low-test-weight corn is only slightly lower than that of corn with test weights of 54 pounds or more. A University of Minnesota study showed that corn with a test weight of 47 pounds had a TDN value that was 98 percent of normal (54 lb/bu) corn. Nevertheless, a low test weight often is a sign of immaturity, and low-test-weight corn often is docked because of higher transportation costs, lower quality for dry milling purposes, and a greater potential for mycotoxins and storage problems. In some situations, it may be advantageous to keep low-test-weight corn separate and market or feed it to reduce dockage on the rest of the crop.
Test weight can be improved by avoiding late planting and by selecting hybrids that have good test weight. Other practices that can help improve the test weight of corn include segregating low-test-weight grain into separate storage facilities, drying grain at lower temperatures, and cleaning grain going into or coming out of storage.