CORN Newsletter: 2009-23, July 21, 2009

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C.O.R.N Newsletter 2009-23
July 21, 2009 - July 28, 2009

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Corn Shorter than Normal this Year?
by Peter Thomison


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Some Ohio farmers are reporting that corn plants are shorter than normal this year. While I believe slower development of corn due to reduced heat unit accumulation is fairly common across the state, I don’t think “short” corn is widespread but probably localized in certain areas of the state, e.g. east-central Ohio.

What would account for these shorter plants and will “shorter” corn have good yields? The following information, which is adapted from newsletter articles by Dr. Dale Hicks, former corn extension specialist at the University of Minnesota, and Dr. Bob Nielsen, corn extension specialist at Purdue University, addresses these questions.

Why are plants shorter? Periods of cool temperatures in recent weeks are the most likely cause of reduced plant heights. Plants grow in height as cells in the internodes enlarge. When the temperature is low, cells don’t grow as big, so internodes are shorter and the plant is shorter compared with normal for the rest of the growing season. (cold temperatures may increase the rigidity of basal internode cell walls, thus limiting cell expansion and internode elongation.) So plants will never catch up in height. Leaves will also be smaller than normal for the same reason. But the leaves on the corn plant now (the first 6 that develop) slough from the plant as the plant grows. And the next few leaves (7 to 10) are on the bottom of the plant after tasseling and do not contribute significantly to grain development, so leaf size for the leaves on the corn plant now should not affect grain yield. The upper leaves that are growing now in size are the ones that will have the greatest impact on yield.

New leaves are initiated from the growing point with about 3 ½ days between the initiations of each leaf. All of the leaves are initiated while the corn plants are very small. Cool temperatures extend the time interval between leaves. The growing point shifts from initiating leaves to tassel because of the night length which is not affected by the cool weather, so there may be 1 to 2 fewer leaves that develop on corn plants this year due to the cooler temperatures that we have already had. A plant with fewer leaves is another cause of shorter plants.

Will shorter plant heights adversely affect yields? Probably not, unless the short height is dramatic enough to significantly reduce canopy cover and harvest of sunlight (and also allow for greater weed competition.) Some early maturity hybrids are shorter than full season hybrids and yield less, so we associate lower yields with smaller plants. Plant size is the “factory” for producing yield so one might expect higher yield potential from larger, taller plants. However, short plants of a given hybrid should produce yields comparable to taller plants of the same hybrid unless the height difference is caused by nutrient deficiency or moisture stress (too much or too little). With regard to short plants observed this year, the height difference is probably due to shorter internodes rather than a major stress and should not affect yield. In planting date trials, late-April planted corn is often shorter than corn planted in May, but produces higher yields so the shorter corn plants we have should not reduce yield potential. A benefit from shorter plants (vs. taller plants) may be reduced risk of stalk lodging due to the lower center of gravity.

References
Hicks, D. 2004. Corn Comments. Minnesota Crop News. Available at http://www.extension.umn.edu/cropEnews/2004/04MNCN13.htm .

Nielsen, R.L. 2001. Short corn at tasseling. Corny News Network, Purdue Univ. Available at http://www.kingcorn.org/news/articles.01/Short_Corn-0712.html .

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C.O.R.N. is a summary of crop observations, related information, and appropriate recommendations for Ohio Crop Producers and Industry. C.O.R.N. is produced by the Ohio State University Extension Agronomy Team, State Specialists at The Ohio State University and Ohio Agricultural Research and Development Center. C.O.R.N. Questions are directed to State Specialists, Extension Associates, and Agents associated with Ohio State University Extension and the Ohio Agricultural Research and Development Center at The Ohio State University.

Information presented above and where trade names are used, they are supplied with the understanding that no discrimination is intended and no endorsement by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.

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Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Keith L. Smith, Director, Ohio State University Extension.

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