CORN Newsletter: 2006-18, June 19, 2006

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C.O.R.N Newsletter 2006-18
June 19, 2006 - June 26, 2006

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Uneven Plant Height in Corn: Effects on Yield
by Peter Thomison


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Uneven corn stands are a hot topic this week and receiving considerable attention across the state. In many corn fields, it’s not unusual to see differences in plant growth stage and height within and between corn rows. Although much of the variability in plant height can be related to uneven emergence, it’s important to recognize that plant height is not a reliable indicator of plant growth stage in corn. In some fields that show variability in plant height, tall and short plants may actually be at fairly similar stages of growth based on leaf collars.

The primary causes of delayed emergence and plant heights are probably soil moisture and temperature variability within the seeding depth zone. Other factors contributing to the problem include poor seed to soil contact due to cloddy soils, soil crusting prior to emergence, seeding depth, residue distribution, etc.

What impact will variability in plant height have on crop yields? It’s been well documented that uneven emergence affects crop performance because competition from larger, early emerging plants decreases the yield from smaller, later emerging plants. According to one popular rule of thumb, if two neighboring plants differ by two or more leaves, the younger plant will almost always be barren or produce a nubbin ear at maturity. In a recent article in the Iowa State University Integrated Crop Management Newsletter (on-line at http://www.ipm.iastate.edu/ipm/icm/2006/6-12/cornheight.html), Roger Elmore and Lori Abendorf reviewed research from Europe, Canada, Argentina, and the U.S. to determine how later emerging plants performed within a field of normal emerging corn. The studies they described usually involved delaying the planting of a certain percentage of corn plants with a field to simulate variable emergence.

Research in Ontario indicated that when one of six (17%) plants was delayed in emergence by two leave overall yield was reduced 4 percent; when delayed by four leaves, 8 percent yield losses were observed. Plants neighboring late emerging plants only partially offset yield losses.

Illinois and Wisconsin research considered the response of corn when 25, 50, or 75 percent of the plants were planted either 10 or 21 days after the original planting date. Overall, grain yields were reduced 6 to 7 percent by a delayed planting of 10 days regardless of the percentage of plants delayed. However, when planting was delayed 21 days, yields were reduced 10 percent when 25 percent of the plants were delayed, 20 percent when 50 percent were delayed, and 23 percent when 75 percent of the plants were delayed.

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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.

All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.

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.

TDD # 1 (800) 589-8292 (Ohio only) or (614) 292-1868


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