DECATUR, Ill. (DTN) -- Cory Ritter finished planting corn this week with one eye on the row and the other on the rain clouds approaching in the distance. The corn portion of the planting season lasted only 10 days start to finish for the Blue Mound, Illinois, farmer -- that includes the three days he sat out idled by rain. A week to plant 900 acres isn't bad, especially when it was put in during the golden window of opportunity to obtain the best possible yields.
The magic planting date to drive corn yield is April 17 in Illinois, said University of Illinois agronomist Emerson Nafziger in a news release this week. He bases that on 35 planting-date trials in central and northern Illinois over the past nine years. Yields in Nafziger's studies didn't differ substantially as long as corn is planted sometime in April. Corn yields were within 1% (about 2 bushel per acre) of the maximum when planted between April 5 and April 30.
"Beyond April, we predict yield losses of about 4% (8 bushels per acre) by May 10, 8% (17 bushels) by May 20, and 14% (29 bushels) if planting is delayed until May 30," Nafziger stated. "We don't have a lot of data for June planting, but the yield loss going into June is at about 2 bushels per day of delay, and it's accelerating."
Ritter said his corn planted one week ago has already emerged. "I haven't had time to take stand counts, but it appears to have all come up at once and looks great," he told DTN. "It's been a good year for emergence." He expects corn planted this week to pop through the ground in five days given soil temperatures and moisture conditions.
Rain showers moved in late Tuesday afternoon and more rain is forecast for his area off and on this week. Ritter still has all his soybeans to plant.
As of April 24, 30% of the corn was planted nationwide, compared to 16% on average. Missouri farmers may have struggled to get a crop in last year, but they lead Midwest farmers this year with 81% planted. According to the most recent Crop Progress report, corn planting for Illinois was 42% completed; Indiana 11%; Iowa 40%; Nebraska 16%, Minnesota 45%, Kentucky 50% and Tennessee 65%.
Soybeans were 3% planted compared to 2% average nationwide with Illinois at 2%; Indiana 2%; Iowa 3%; Missouri 5%, Minnesota 34%, Kentucky 22% and Tennessee 22%.
Nafziger's research team also gathered 23 site-years of planting-date data for soybeans in the same sites as their corn studies. The earliest planting date for soybeans was in the second week in April, with the latest dates in mid-June.
The data for soybeans showed that the maximum yield was obtained in mid-April, and that yield loss by the end of April was about 4 percentage points, or about 2.5 bushels. After April, losses totaled 7% (4 bushels per acre) by May 10; 10% (7 bushels) by May 20; 16% (11 bushels) by May 30; 21% (14 bushels) by June 10; and 29% (19 bushels) if planting was delayed to June 20.
"On a percentage basis, these loss numbers are slightly greater than those from planting delays in corn, but some of this is due to planting soybeans a little later in April than we started planting corn. Both crops lost yield at about the same rate if planting was delayed into late May," Nafziger noted in his release. "That runs counter to the earlier findings that corn loses yield faster when planting is delayed, and therefore needs to be planted earlier."
Given that neither crop suffers dramatically from planting through early May, farmers might assume that planting priorities for both crops are similar. However, corn seedlings tend to emerge better than soybeans under soil conditions typical of early spring, so Nafziger still suggests starting with corn, at least until soils warm up to allow faster soybean emergence.
"While getting both crops planted on time is beneficial, we shouldn't lose sight of the fact that yield losses for delays into and even past mid-May are not so large that we need to give up hopes for a good crop if we aren't done planting by the end of April," Nafziger said.
Ritter remains optimistic, but he'll feel better when the soybeans are tucked into the ground. Then he'll welcome nice gentle showers.
More details and data from Nafziger's field studies are available at: http://bulletin.ipm.illinois.edu/…
Pam Smith can be reached at email@example.com
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