Purdue expert offers update on corn hybrid maturities for late plantings

It’s been a stressful and wet spring for local farmers, and Purdue corn expert, R.L. (Bob) Nielsen, said time is running out for some Indiana fields not yet planted to their intended corn crop or those fields already planted to corn that now require replanting. Many fields are currently too wet to allow for planting and time will tell if conditions improve in the near future.

On Nielsen’s website, the “Chat ‘N Chew Café,” he recently offered an article updating approximate “safe” hybrid maturities for various dates and various locations in Indiana. In his data, Whitley County was one of six Indiana reference sites in an easy-to-read table.

Nielsen said there are two challenges with regard to choosing hybrid maturities to plant in early June in Indiana. “One relates to whether the chosen hybrid maturity will mature safely (i.e., kernel black layer) before a killing fall freeze,” Nielsen said. “The other is whether the chosen hybrid maturity will mature early enough to allow enough time for the grain to dry to acceptable harvest moistures.”

Nielsen described the process for estimating “safe” hybrid maturities suitable for late planting in an earlier, more lengthy article on his website (see below for URL).

“The choice of the desired date to reach kernel black layer influences not only the estimate of available Growing Degree Days (GDD) from planting, but also the likely grain moisture loss (drydown) per day after maturity,” he said. “If your primary objective is to simply mature the crop before a killing fall freeze in early to mid-October, then you can use a later maturity hybrid and take advantage of another couple weeks of GDDs. If you want the crop to mature in late September to take advantage of relatively better field drydown conditions, that will by necessity require planting an earlier relative maturity hybrid because of the fewer available GDDs. The difference in estimated ‘safe’ relative hybrid maturities between the two decisions can be dramatic.”

Nielsen provided a table that provides estimates of “safe” relative hybrid maturities for two planting dates (June 5 and 10) for six select counties across the state (different geographic locations) and three targeted crop maturity dates in the fall (Sept. 20, Sept. 30, and Oct. 10). “These estimates are based on the procedure described in my lengthier article,” he said.

In the data provided, Nielsen suggested that producers in or near Whitley County who plant on June 5 would have approximately 2,058 available GDDs for a target black layer date of Sept. 20, 2,172 GDDs for a Sept. 30 target, and 2,266 GDDs for an Oct. 10 target. In these scenarios, the approximate hybrid Comparative Relative Maturity (CRM)* needed would be 95, 99, and 103 day corn, respectively. If planting June 10, producers in or near Whitley County would have approximately 2,000 GDDs for a target black later date of Sept. 20, 2,102 GDDs for a Sept. 30 target, and 2,196 GDDs for an Oct. 10 target. In these scenarios, the approximate hybrid CRM needed would be 94, 98 and 101 day corn, respectively.

“Bottom line is that the time is approaching when the ‘safe’ relative hybrid maturities for delayed corn planting will simply be too unadapted for most growers’ liking, both from the lower yield potential perspective and typically unsatisfactory genetic disease resistance,” Nielsen said. “Factor in the economics and crop insurance considerations (June 5 cutoff for full coverage, same for prevented planting with some policies), then the window for corn planting is beginning to close.”

You may want to be in communication with your crop insurance provider for details and options for your individual situation.

For complete information, visit Nielsen’s original article at kingcorn.org/news/articles_17/SafeMaturities-0523.html or his longer article (referenced above) at agry.purdue.edu/ext/corn/news/timeless/HybridMaturityDelayedPlant.html. A related article, “Corn Replant Considerations 2017” is also worth a read agry.purdue.edu/ext/corn/news/Articles_17/CornyDecisions-0508.html.

— John Woodmansee is an extension educator for Whitley and Noble counties.

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