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Hill and Furrow

Why are these corn ears so different? How might this difference affect yield estimates?

While my inclination is to joke and say that the obvious difference must be that the larger ear was grown in Illinois while the smaller ear was grown in another state (four letters, also starts with an 'I'…..), this isn't it.

A estimate of yields in a field full of the more moderate-sized ear (612 kernels/ear) at an ear population of 33,000 would be 260 bu/A. While estimated  of a field full of the larger-sized ear (882 kernels/ear), at the same ear population would be 364 bu/A (Figure).

These would be phenomenal yields if both estimates were to prove accurate, and record shattering yields for the field with the larger ears. Yield estimates can influence many of a farmer's decisions going forward including locking in higher grain prices before harvest for guaranteed future delivery. This is why representative and conservative estimates of yield are so important.

I will not hold you in suspense any longer....... The monster ear was picked from an outside row, while the more typical-sized ear was representative of the ears that were growing in the middle of the same field. Those plants growing in the outer row of a field likely have greater access to sunlight, growing space and perhaps nutrients than plants growing in the rest of the field and can significantly and inaccurately elevate estimates of potential grain yield. More accurate estimates can be found by following the recommendations that were laid out Dr. Emerson Nafziger in a recent Bulletin article.

Northwestern Illinois Ag R&D Center senior research specialist Marty Johnson (Figure) and I spent part of yesterday afternoon collecting yield estimates in the center's corn planting date research trial (Table).

Planting Date

R1 Date

Yield estimate

April 5

July 1


April 15

July 1


May 5

July 13


May 19

July 18


Only time will tell how the weather conditions that the crop experiences throughout the rest of the growing season will affect the final yields in these plots.