CORN Newsletter: 2009-14, May 18, 2009

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C.O.R.N Newsletter 2009-14
May 18, 2009 - May 26, 2009

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Planting Delays and Switching to Earlier Maturing Corn Hybrids
by Peter Thomison


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Persistent rains have caused major delays in corn planting across Ohio. According to the USDA/NASS (http://www.nass.usda.gov/) as of Sunday May 17, Ohio corn acreage planted, at 39 percent, was 13 percent behind last year and 43 percent behind the five year average. Corn emerged was 18 percent, compared to 26 percent last year and 46 percent for the five year average. The weather forecast for the next couple of days looks promising with warmer temperatures and the absence of rain, so hopefully as soggy fields dry, corn planting will be completed soon.

Is there a need to switch from full season to shorter season hybrids due to these weather delays? Probably not - in most situations full season hybrids will perform satisfactorily (i.e. will achieve physiological maturity or "black layer" before a killing frost) even when planted as late as May 20-25, if not later in some regions of the state.

Results of studies evaluating hybrid response to delayed planting dates indicate that hybrids of varying maturity can "adjust" their growth and development in response to a shortened growing season. A hybrid planted in late May will mature at a faster thermal rate (i.e. require fewer heat units) than the same hybrid planted in late April or early May).

In Ohio and Indiana, we've observed decreases in required heat units from planting to kernel black layer which average about 6.8 growing degree days (GDDs) per day of delayed planting. Therefore a hybrid rated at 2800 GDDs with normal planting dates (i.e. late April or early May) may require slightly less than 2600 GDDs when planted in late May or early June, i.e. a 30 day delay in planting may result in a hybrid maturing in
204 fewer GDDs (30 days multiplied by 6.8 GDDs per day).

There are other factors concerning hybrid maturity, however, that need to be considered. Although a full season hybrid may still have a yield advantage over shorter season hybrids planted in late May, it could have significantly higher grain moisture at maturity than earlier maturing hybrids if it dries down slowly. Moreover, there are many short to mid season hybrids with excellent yield potential. Therefore, if you think you may end up planting in late May, consider the dry down characteristics of your various hybrids. In past years, some mid to full season hybrids had grain moisture levels at harvest similar to those of short season hybrids because of rapid dry down rates. Keep this in mind before you trade the hybrids you originally planned to use for shorter season alternatives. Also, late planting dates increase the possibility of damage from European corn borer (ECB) and warrant selection of ECB Bt hybrids (if suitable maturities are available). In recent OSU studies, Bt hybrids planted after the first week of June consistently outyielded non-Bt counterparts even at low to moderate levels of ECB. Since many corn growers will be planting triple stack hybrids this year, which include Bt resistance for ECB, this may be a non-issue unless there’s a need to switch to earlier maturing hybrids.

Corn planting in the northern third of Ohio is most likely to be impacted by more wet weather. If planting delays continue beyond next week, growers in parts of northeast and north central Ohio may want to consider corn hybrids that require 100 to 150 fewer GDD than the adapted full season hybrids usually planted. These areas of the state historically accumulate fewer GDDs during the growing season than other regions of Ohio. For more information on selecting corn hybrids for delayed planting, consult "Delayed Planting & Hybrid Maturity Decisions", a Purdue/Ohio State University Extension publication available online at: http://www.agry.purdue.edu/ext/pubs/AY-312-W.pdf .

Readers can subscribe electronically to this newsletter by signing up at http://agcrops.osu.edu/services/email.html. E-mail labarge.1@osu.edu if you have problems subscribing or no longer wish to receive this newsletter.

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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