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College of Food, Agricultural, and Environmental Sciences


Health of Ohio's Corn Crop in Question

July 21, 2005

COLUMBUS, Ohio — One thing that can protect Ohio's corn crop from drought damage is an element that the crop is lacking — ironically, driven by inadequate moisture.


Some of Ohio's corn crop is experiencing a deficiency in potassium, a major nutrient for water use efficiency and easing drought-driven stresses. However, because of the lack of adequate soil moisture, the plants are unable to access the potassium readily available in the soil.

"It's a double whammy for this corn crop, already in a dire situation with shallow roots, uneven development and the potential for pollination problems," said Peter Thomison, an Ohio State University Extension agronomist.

Robert Mullen, an Ohio State University soil fertility specialist with the Ohio Agricultural Research and Development Center, added that the crop's shallow roots, early season wet conditions and a low soil pH are all contributing factors to a potential potassium deficiency.

A clear sign of a potassium deficiency is necrosis of the lower leaves, which eventually progresses to the leaf base along the main leaf vein. Not much can be done to right a potassium deficiency problem, especially during silking when the plant potentially takes up all of the potassium it's going to use. And potassium deficiencies can lead to stalk lodging problems as harvest approaches.

According to the Ohio Agricultural Statistics Service, close to half of the state's corn crop is silking, a stress-sensitive time of development when the level of pollination success will ultimately determine yields. Continued lack of rainfall during pollination may impact how well the crop develops ears.

"Adequate moisture is important during the pollination period, primarily to ensure that the corn plant synchronizes flowering. Corn is unique in that it has both male and female flowers," said Thomison. "What typically happens under severe water stress is that the male flowers (the tassels) may shed pollen before the female flowers (the silks) have emerged from the husks. You get what is known as asynchronous flowering and you may end up with scattered kernels on an ear. If the stress is particularly severe, as it was in some areas of Ohio in 2002, you may end up with no ear and barren plants."

Thomison said that uneven plant growth in fields, where some plants are taller than others, is a sure sign that some yield potential has already been lost. Many fields across Ohio are already experiencing this problem.

"Unfortunately we have fields that are only waist high. When you have crop development that has been curtailed that much you are looking at a smaller photosynthetic factory," said Thomison. "That little plant simply isn't going to be able to produce enough sugars as a plant twice as tall would. You can put on an ear with a plant six or seven feet tall, but with a plant half that height there is not enough leaf tissue to produce a normal yield."

Corn growers are still hoping for rain; some have been blessed with as much as six inches of rain from scattered showers over the past several days. But where that's the exception rather than the norm, growers should be prepared to make the best use of their corn crop if low yields stifle the crop's potential as grain.

Candace Pollock
Peter Thomison