Sept. 13, 2019

The year was one of the worst planting seasons in a long time. It kept raining when we wanted to plant in April and May. When crops finally were planted, to add insult to injury, it was hot and dry.

Dave Nanda, Ph.D., SGD director of genetics, expects a lot of corn to be harvested with high grain moisture. This may result in lower test weight grain which may affect its price. Is test weight important? Grain moisture is important because of cost of drying, but why is test weight important? Facts about test weight and why it is significant are below:

Test weight of grain is a ratio between weight and volume of grain. It is measured as weight of grain that fills a quart container. There are 32 quarts in a bushel basket.
Corn grain is marketed in the U.S. on the basis of 56 lbs. test weight per bushel.
Corn with 56 lbs. per bushel is considered “NO. 1 yellow corn” and 54 lbs. is called “NO. 2 yellow corn” at 15 percent grain moisture.
Farmers can haul more bushels of high test weight grain in the truck per trip to the elevator than low test weight grain.
Grain with lower than 56 lbs. test weight may be discounted by the elevators but no credit given for higher test weight.
Grain with higher test weight is generally considered to have better quality.
Hybrid genetics play an important role in test weight determination. However, there is no correlation between test weight and yield potential of a hybrid.
Some of the highest yielding hybrids have average test weight. (During Nanda’s work as a corn breeder, he developed a couple of widely grown hybrids which had high yields and high test weight, hybrids that corn breeders dream about and work for years to develop.)
As the kernel moisture goes down, test weight increases since dry matter of the grain weighs more the moisture in the grain.
Higher test weight grain with orange color has greater eye appeal, its integrity is maintained during shipping and is generally preferred by the customers in foreign countries as compared to lower test weight, chaffy grain.

There are many factors that can affect test weight:

Hybrids with genetic potential for higher test weight will generally yield grain with higher test weight.
Generally, earlier planting leads to higher test weight grain.
Higher temperatures with ample moisture tend to increase test weight if kernels are fully mature.
Drought stress decreases test weight because it affects the photosynthetic process of the plants.
Late season leaf diseases such as southern leaf blight or southern rust, anthracnose leaf blight and Goss’ blight decrease test weight since they can interrupt the grain-fill period and proper grain development.
Ear rot diseases such as diplodia, gibberella or aspergillus will have a negative effect on test weight.

Effect of test weight on 2019 corn yields