URBANA – April 2013 turned into a "second March," with wet weather and cool temperatures persisting into the last week of the month and corn planting progress in Illinois stuck at 1 percent as May 1 approached. Nationally, only 5 percent of the corn crop was planted by April 28, and none of the Corn Belt states had more than 2 percent planted, according to University of Illinois crop sciences professor Emerson Nafziger.
"The corn that has been planted is struggling mightily to survive the soil conditions and to emerge," Nafziger said. "If we are lucky enough to 'skip' another month and May begins to look more like a typical June, it's not too late to get the planting and crop back on track."
Nafziger said that while yield potential will start to drop as planting gets further into May, chances of a good corn crop remain high as long as weather permits planting soon, and then returns to a more normal pattern of rainfall without summer drought periods like parts of Illinois has seen for the past three years.
"Most of our planting-date studies show that yield loss accelerates as planting is delayed in May, and getting corn planted by the end of April is a recognized goal in Illinois," Nafziger said. "The reality is though, that on average, we only manage to get a little more than 40 percent of our corn planted by this target date, and it's nearly the end of May before we reach 90 percent is planted."
Nafziger said there have been several times in recent years in which more than 50 percent of the corn crop has been planted in a 10-day period, and it could be even faster if all fields are ready at once.
This means that weather and soil conditions, not equipment, are the major barriers to planting early.
"Despite our anxiousness to finish planting by the end of April, Illinois data over the past 20 years do not show that early planting alone boosts yields," Nafziger said. "In fact, there is no correlation between time to 50 percent planted and yield as measured by departure-from-trendline yield. It's clear that the early planting and drought-damaged yields of 2012 helped wreck this correlation, but even if we eliminate 2012, the percent planted by April 30 still explains only about 5 percent of the yield departure from trend," he said.
Does this mean that getting the crop planted early is not as important as a management goal? Nafziger said no.
"Planting before the end of April generally means that we've removed late planting (and the shortened season and greater chance of stress that follow late planting) as a potential barrier to high yields, thus maximizing yield potential. At the same time, we need to recognize that it's not 'game over' if we are forced by weather and soil conditions to plant into May, even past mid-May," he said.
Nafziger said the fact that early planting does not necessarily lead to high yields does indicate that what happens after planting and through the rest of the season is more important than when the crop is planted.
"This reminds us that it's important not to do anything that might compromise the plant's ability to take advantage of conditions later in the season that will determine actual yield. That certainly includes taking care not to plant into wet, compacted soils in our rush to plant early," he said.