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Patience is Painful, But Still Best Bet for #CornPlant19

Staying with original crop plans and hybrid selection is recommendation from researchers.

With each passing day, the wait to plant corn is a little more painful. 

As of May 6, corn planting is only 23% complete in the nation’s 18 largest corn-producing states, according to USDA’s National Ag Statistics Service. That’s half the progress of corn planting in any other year, NASS reports.

The question of how much yield farmers have lost to weather delays is not easy to answer, although Gary Schnitkey and Carl Zulauf have tried in the May 7 edition of Farm Doc Daily.

The economists at the University of Illinois Department of Agricultural and Consumer Economics and Ohio State University’s Department of Agricultural, Environmental and Development Economics, respectively, report that more often than not, late planting reduces overall yield. 

They cite corn planted late in northern Iowa and southern Minnesota last year, due to wet weather. County yields near the Iowa-Minnesota border were below trend in 2018, both for corn and soybeans. According to FarmDoc Daily, April 9, 2019, yields in those areas averaged about 30 bushels per acre less for corn, 10 bushels per acre less in soybeans, from long-term averages. 

There are exceptions. In 2009, much late planting of corn occurred and national yields were still 10 bushels above trend. 

Planting date accounts for 10% to 20% of yield variation, according to a recent report from the Iowa Soybean Association’s On-Farm Network. That means nearly every other aspect of crop management are of greater importance than planting date. 

The bottom line? 

“The biggest mistake that can be made is to rush into fields that are too wet for planting to achieve planting by a calendar date,” says Scott Nelson, Iowa Soybean Association’s (ISA) On-Farm Network director. “Like all of farming, patience in waiting for fields to dry is the key to success in 2019.”

Do I Need to Change to a Shorter-Season Hybrid?

The later planting season gets, the more tempted farmers may be to change to a shorter-season corn hybrid. It’s too early for that, notes Pioneer agronomist Larry Lunder. 

Only about 60 to 70 growing degree units occur during the first 10 days of May. That’s enough to get the corn germinated and out of the ground but not a lot in the big picture. 

“The thing is, don’t overreact this time of year. If you switch to an earlier maturity hybrid, that alone can cost you yield potential,” Lunder says. “Continue to go out and plant your chosen maturity.”

In most situations, full-season hybrids will continue to be your best bet for a few more weeks. 

Peter Thomison, Extension agronomist at Ohio State University, writes in this week’s Ohio State CORN Newsletter, 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).”

Thomison notes researchers at Ohio State and the University of Illinois observed decreases in required heat units from planting to kernel black layer, that 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).

Adds Lunder, “If it happens we get beyond say the 20th or 25th of May and you still haven’t been able to get in the field, then you might look at getting an earlier maturing hybrid.”

There is a caveat: A longer-season hybrid could dry down slower than shorter-season hybrids and, therefore, have higher grain moisture at physiological maturity. If that’s a concern to you, consider switching to a short- to mid-season hybrid, Thomison notes.

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