Planting delay lengthens, decisions needed
URBANA As the planting delay lengthens, many growers are wondering if they should switch crops from corn to soybean, and if they should change corn hybrids from earlier to later ones.
Illinois may be “ahead of the rest of the Corn Belt, but with only about 10 percent planted in April, it’s a disappointing start after the dry weather in early April,” said Emerson Nafziger, University of Illinois Extension agronomist.
As of Sunday, just 8 percent of Iowa’s corn acres had been planted and is said to be one of the slowest planting starts in a decade.
Data show that losses to delayed planting accelerate earlier and faster in corn than in soybean, meaning that soybean becomes a more profitable choice at some point in time. At current crop prices and production costs, this does not happen until early June in Illinois.
“If you have already made crop-specific investments such as applying N fertilizer for corn, this will provide more incentive to stay with corn,” he said. “This is certainly not a decision to rush into at this point.”
A more immediate decision some are considering is whether to switch to an earlier hybrid, or lining up seed so that such a switch can be made. Nafziger said some northern Illinois growers need only look back to 2009 to find a year when later hybrids didn’t do well when planted late. Switching from a mid- or fuller-season hybrid to an early hybrid means trading one set of risks for another, he said.
“If we plant in early May, the hybrids we typically use will accumulate all the growing degree days they need anywhere in Illinois,” he said.
But if planting is delayed until June 1, the growing degree days (GDD) accumulated by the end of September average only about 2,450, 2,700 and 2,800 in northern, central and southern Illinois, respectively. This is enough GDD to mature most mid-season hybrids grown in these regions, except in northern Illinois, where mid-season hybrids may be rated around 2,500 GDD.
“Research in Indiana and Ohio has shown that late-planted corn usually (but not always) requires fewer GDD than when the same hybrids are planted early,” he said. “This means lower risk of not receiving enough GDD by frost for late-planted corn, but the reduction in GDD requirement is associated with yield loss, so that’s not all positive.”
Nafziger said it is clear that most of the hybrids growers plan to plant this year should not be switched out for earlier hybrids until and unless planting is delayed to late May or early June. Even then, it’s likely that first-choice hybrids may do better than those earlier hybrids growers would use to replace them, especially in the southern half of the state.
“Bringing early hybrids less than 105-day RM into the southern half of Illinois may lower risk of frost before maturity, but it also means moving them from their primary area of adaptation into an area where they have not been tested or sold as first-choice hybrids,” he said. “In many cases, that does not turn out very well.”
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