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C.O.R.N Newsletter 2009-16
     June 2, 2009 - June 9, 2009


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Predicting leaf stage development in corn.
by Peter Thomison

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Dr. Bob Nielsen at Purdue University has described a method for predicting leaf stage development using accumulated heat unit or growing degree day (GDD) information. Given an understanding of corn leaf stage development and heat unit calculation, a grower can predict what leaf stage of development a particular field is at given its planting date and temperatures since planting. It is useful to know when the crop emerged, but if you do not, you can estimate that event also. Corn emergence typically requires 100 to 150 GDDs.
Dr. Nielsen proposes that corn leaf developmental rates may be characterized by two phases. From emergence to V10 (ten visible leaf collars), leaf emergence occurs approximately every 82 GDDs. From V10 to tasseling, leaf collar emergence occurs more rapidly at approximately one leaf every 50 GDDs. Previously, about 60 to 65 GDDs were associated with the appearance of new leaf collars during vegetative growth.
Example (from reference noted below): A field was planted on April 28, but you do not know exactly when it emerged. Since planting, approximately 785 GDDs have accumulated. If you assume that the crop emerged in about 120 GDDs, then the estimated leaf stage for the crop would be about V8. This estimate is calculated by first subtracting 120 from 785 to account for the estimated thermal time to emergence, then dividing the result (665) by 82 (equal to 8.1).
Dr. Nielsen cautions that these predictions of leaf stage development are only estimates. One of the factors that most influences the accuracy of these estimates is the existence of other growth-limiting stresses and conditions (nutrient deficiencies, compaction, etc.). Despite these potential drawbacks, this method may be useful in timing when plants will reach an approximate stage of growth.

For more on Dr. Nielsen’s prediction system, check out the following –

Reference
Nielsen, R.L.. 2008. Use Thermal Time to Predict Leaf Stage Development in Corn
Corny News Articles, Purdue Univ. [On-Line]. Available at http://www.agry.purdue.edu/ext/corn/news/timeless/vstageprediction.html (URL verified 6/1/09)

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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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