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C.O.R.N
Newsletter
2009-25
August 3, 2009 -
August 10, 2009
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Kernel Development Well Underway in Early Planted Corn
by
Peter Thomison
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Many Ohio corn fields received over an inch of rain last week. This rainfall in combination with good rainfall the previous week and unseasonably mild temperature have helped minimize the soil moisture deficits some areas were still experiencing. Brown silks are common and kernel development is well underway in corn fields that were planted in April and early May. Following pollination, kernel development (or grain fill) is the most critical period in the development of the corn plant for the determination of grain yield. Kernel development proceeds through a number of stages which have been characterized by such terms as blister, milk, roasting ear, soft dough, dent, etc. Since these descriptive terms can sometimes be difficult to interpret, alternative systems have been proposed. A staging system widely used by agronomists and crop consultants divides kernel development into six stages, designated numerically as R1, R2, through R6. Below lists kernel developmental stages in sequence and provides a brief description of each phase.
Stage, Description (Avg. No. Days/Stage, Avg. Days from Silking)
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Silking (R1), fresh green silks, no visible blisters (4, --)
Pre-Blister, silks brown, not necessarily dry visible kernel pimples, contain little clear fluid (4, 8)
Blister (R2), visible blisters w/abundant fluid (4, 12)
Early Milk, mostly white kernels w/milky-white fluid, some yellow kernels (4, 16)
Milk (R3), mostly yellow kernels w/milky-white fluid, no solids yet, “Roasting Ear” stage (4, 20)
Late Milk to Early Dough, solids beginning to form, kernel pasty texture and barely edible (4, 24)
Soft Dough (R4), pasty or semi-solid, not edible, no visible denting (5, 28)
Late Dough to Early Dent, few kernels beginning to dent, especially near butt of ear (5, 33)
Dent (R5), majority of kernels dented or denting (8, 38)
Late Dent, essentially all kernels dented, milk line may just be visible (17, 52)
Black Layer (R6), maximum kernel dry weight, kernel moisture 27-32% (10, 62)
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Note on R-Stages 1 through 6: specific number of days associated with each stage may vary from season to season, from location to location, and from hybrid to hybrid.
Keep in mind that the values for average number of days per stage and approximate days from silking in the table above are based on timely corn planting (e.g. early May). When corn is planted later, it generally requires fewer heat units to achieve R6, physiological maturity or “black layer”, and this may affect the number of days per stage and days from silking. For more on grainfill check out the following article that Dr. Bob Nielsen which excellent pictures and diagrams:
Nielsen, R.L. (Bob). 2008. Grain Fill Stages in Corn. Corny News Network, Purdue Univ. [online] http://www.kingcorn.org/news/timeless/GrainFill.html. [URL accessed 8/3/09].
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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,
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and the Ohio Agricultural Research and Development Center
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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.
TDD # 1 (800)
589-8292 (Ohio only) or (614) 292-1868
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