Do Large Corn Ears Mean High Yields?
DR. DENNIS B. EGLI
LEXINGTON, KENTUCKY
Is ear size a reliable indicator of corn yield? It all depends. If ‘large’ means ears where most of the flowers produce kernels, the answer is probably yes. We all know that stress during pollination and kernel set can reduce the number of kernels per ear. Partially filled ears are usually an indicator of reduced yield. So, ear size is an indicator of yield.
It’s possible, however, that an increase in kernel size (weight per kernel) can compensate for the reduction in kernel number and reduce the effect of the reduction in ear size on yield. Compensation occurs when the stress is relieved during seed filling, resulting in larger kernels. Unfortunately, the increase in kernel size is limited and it may not be enough to prevent yield loss. From the viewpoint of kernels per ear, ear size is usually related to yield.
Ears that are completely filled to the tip are usually taken as an indicator of maximum yield. Strange as it may seem, this is not always true. Completely filled ears in a highly productive environment can be an indication that yield was left in the field because there were not enough flowers available to convert all of the productivity of the crop into yield. This situation occurs when the population is too low (not enough ears per acre), increasing population in this situation will increase the flowers per acre and the crop will be able to convert all its productivity into yield.
So, we have a dilemma – unfilled kernels at the tip of the ear can indicate stress that reduced the number of kernels per ear and probably yield or it can indicate that the number of flowers was not limiting, and yield was at a maximum. Nothing can be done about unfilled kernels (except hope for better weather next year), but if all the ears are filled to the tip, you might want to consider bumping up your population next year.
Ear size (flowers per ear) is also under genetic control, so it can vary among hybrids. Genetic differences in ear size do not directly influence yield, but they do affect the population needed to produce maximum yield. Hybrids with small ears need higher populations to produce maximum yield than hybrids with large ears. For example, the population producing maximum yield with an ear size of 480 potential kernels per ear is roughly 44,000 plants per acre for a crop yielding 250 bushels per acre. Increase the ear size to 576 kernels per ear and the optimum population drops to about 37,000 plants per acre for the same yield. Genetic differences in ear size did not affect yield because yield is determined by the productivity of the crop, not the number of potential kernels (ear size). In other words, just increasing ear size does not increase the productivity of the crop, it only increased the potential kernel number. But ear size will influence the population required to produce maximum yield.
Environmental conditions during ear development also influence ear size (flowers per ear), although much of the research on this topic suggests that the changes are relatively small.
Ear size-yield relationships are complicated. The key to understanding them lies in the source of the variation. If kernels per ear (effective ear size) is reduced by stress during pollination and kernel set, yield will probably be reduced. In this case ear size (kernels per ear) is related to yield. Genetic differences in ear size are not related to yield, but they will affect the population needed for maximum yield. So, ear size may or may not affect yield. It all depends. Always remember – “A river cuts through rock, not because of its power, but because of its persistence” (Mark Bradburn, Financial advisor). ∆
DR. DENNIS B. EGLI
UNIVERSITY OF KENTUCKY