Assessing Potential Corn Yield Losses from the Drought

Even with the rains near the end of last week, corn in some fields has been severely damaged by a lack of water. Some farmers are calling insurance adjusters trying to decide if they can cut the corn for silage to get something from their crop. In most cases, the farmer would have to leave a strip or strips of corn in the field for yield estimates later. The concern with this is that the corn could end up doing better than expected. A farmer's worst-case scenario is cutting the corn for silage, leaving those strips of standing corn, and having rains that turn the crop around and yield 71% of the 5-year average, and the field was insured at 70% of the 5-year average.

If possible, let the corn get through pollination. Corn ears with less than 400 kernels per ear likely have yield loss. Corn with 300 kernels or less will likely have yield losses that trigger crop insurance. Table 1 below lists the yield components that make yield, including ears per acre, kernels per ear, and kernel size (listed as kernels/bushel). Ears per acre and kernels per ear determine the number of kernels per acre. Kernels per acre divided

Table 1 includes three kernel sizes, 80, 90, and 100 thousand kernels per bushel. Good weather during seed fill will usually get most cornfields close to 80 thousand kernels per bushel. Very stressful conditions will result in smaller kernel sizes and get corn-fields closer to 100,000 kernels per bushel.

A corn crop cannot makeup yield for very low kernel numbers. For example, if a corn field only has 200 kernels per ear, but has a good seed filling weather, it may have larger kernels. However, yields may only get to 75 bushels per acre. Conversely, if a corn field has 400 kernels per ear, but poor seed fill conditions, the field might yield 120 bushels per acre.

Estimating yield is not an exact science. The farmer probably needs to grab 20 or more ears in a field to estimate kernel numbers per ear. The estimate is only as good as sampling area. If the farmer choses the worst spot of the field or the best spot of the field, that will skew the estimate yield one way or the other.