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NOW is the time to plant?

Published April 5, 2012
University of Illinois crop sciences professor Emerson Nafziger says that almost nothing about the spring of 2012 in Illinois has been normal. Rainfall was below average over most of the state, with March temperatures breaking records on a record number of days.

According to the Illinois Weather & Crops report issued by the Illinois office of the National Agricultural Statistics Service, an astounding 5 percent of the Illinois corn crop was planted by April 1, with 1 percent planted by March 25. Over the past 20 years, there were only two in which there were reports of corn being planted by the first Sunday in April. In a few other years with dry weather in early April, farmers were described as "anxious to start planting" but it is clear that almost no one thought that planting that early was a good idea.

This year, most of Illinois remains dry in the middle of the first week of April. "While planting is getting a serious start in some areas, others are still waiting until the crop insurance date at the end of this week, or until after Easter," said Nafziger.

One reason for waiting is that the weather forecasts, particularly models of temperatures over the next seven to ten days, will be soon be updated to extend past the middle of the month. According to Nafziger, "While we all know that weather forecasts can change suddenly, as we approach the middle of April, we should get a clearer idea of whether or not the emerged crop could be in trouble."

A major cause of concern is the possibility of a late frost harming the emerged crop. According to 30-year weather data summarized by the Midwest Regional Climate Center (, the median dates at which temperatures of 32 degrees last occur in the spring are in late April in northern Illinois and in mid-April farther south in the state, with the earliest last freeze of the spring occurring in late March.

"If we're optimistic and assume that the pattern we have had so far this spring will hold, we might not have to lose too much sleep over concerns that the emerged crop will freeze," Nafziger said.

With temperatures continuing to stay well above normal, the crop continues to emerge rapidly. "The plot we planted at Urbana on March 16 has reached to two-leaf stage, with good stands and in very good condition," said Nafziger. "That crop has received about 275 growing degree days since planting."

There are indications that temperatures may drop over the next week, meaning that growing degree days (GDD) accumulations will return to more normal levels. GDD accumulation for March has averaged only 67 GDD over the past ten years at Urbana; in 2012 it was 233, about 50 percent higher than in any of the previous years. Average GDD accumulations in April and May have been 166 and 374. "That means that corn planted on April 1 in a normal year will not grow as much by May 1 as the corn planted in mid-March grew by April 1 in 2012," explained Nafziger. A return to normal temperatures will slow growth, but the effects of the warm temperatures up to now will continue to have the crop developing ahead of normal.

Soil temperatures remain above average, but soils are dry and daily temperature fluctuations are relatively large. This is because water in soil holds heat better than mineral material or air. If night temperatures drop into the 30s, the warm soil protects the leaves from frost damage by radiating heat to them even as the leaves radiate to the sky. This will not help for long if temperatures drop to freezing or below.

The question is: Now that it's April, is there any reason to wait much longer to start planting?

According to Nafziger's planting date data from the last five years, "Planting on April 20 produced the highest yield of 201 bushels an acre and planting on April 30, May 10, May 20, and May 30 yielded about 2, 7, 15, and 27 bushels less than the highest yield, respectively." If this year follows the same pattern, corn planted on April 1 or April 10 will yield 7 and 2 bushels less, respectively, than corn planted on April 20.

The only agronomic issue at this point besides the ongoing concern about whether the weather pattern will change for the worse is whether there is enough soil moisture to allow seeds to germinate. This is a particular concern in fields where soils were tilled some time ago and where the lack of rain has meant that surface soil has continued to dry.

"Whether to plant into dry soil with the idea that seeds will germinate quickly once it rains is a common issue in late May with soybeans, but not in early April with corn," explained Nafziger. Corn seed needs to take up less water than soybean seed to emerge. If soils stay relatively dry, corn seeds tend to stay viable even if the weather is too cool or too dry for emergence.

"It's probably not a good idea to till again to try to bring up moisture; that could result in uneven distribution of soil moisture down the row, causing unevenness in emergence, which can reduce yields," he said. "Soils in most tilled fields are already fairly fine by now, even after only one tillage pass, and more tillage would lead to more soil moisture loss and would add to the risk of crust formation after heavy rain."

So -- it looks as if, in 2012, the corn crop planting is on course to be the earliest ever, assuming that the current weather pattern continues. Concerns related to the possibility of deteriorating weather conditions diminish with each day. Planting should accelerate over the next week. With luck, including getting some rain in the coming weeks, the crop will be off to a good start.

For now, the focus should be on getting corn planted first. Recent data show good yields from planting soybeans in April, and if they can be planted under good conditions, there is little need to wait until May to start to plant soybeans.