USDA’s crop progress report this week shows corn planting 72% behind the five-year average in Illinois and not much better in Indiana or its surrounding states. With more rain likely in the next few weeks and the corn-planting window closing rapidly, many farmers in these areas could end up switching their corn acres to soybeans, says Drew Lerner, World Weather, Inc.

“We’ll see some planting progress being made shortly from northern Missouri into Indiana, but I see no prolonged dry period ahead,” says Lerner. “The last days in May will likely be dry for this area, but then it will rain again in early June.

“Poorly draining fields in northern and central Illinois and in west-central and north-central Indiana will likely need to switch to soybeans or risk major yield reductions in corn,” adds Lerner. “On the other hand, growing conditions this summer should be pretty good once the crop is established.”

In general, rainfall will be plentiful, heat stress should be limited and the frost threat subdued for the 2009 corn-growing season, predicts Lerner. “I think there’s going to be a lot of moisture around throughout summer,” he says. “It’s not going to be a very hot summer, particularly for the northern and eastern Corn Belt, and I’m not expecting any earlier-than-normal frosts or freezes.”

Farmers who are currently struggling to plant corn on time should therefore hone a sharp pencil before making the decision to switch to soybeans, says Bob Nielsen, Purdue University Extension agronomist. “Predicting lost corn yields from late planting can be pretty tough,” says Nielsen. “If conditions for the rest of the year are perfect, we may still be looking at 150-180-bu. yields, even with late planting. So, at least through the end of May, I would encourage corn growers to think about planting shorter-season corn hybrids rather than switching to soybeans. After that, it’s kind of a toss-up on what to plant.”

Corn growers who have already applied anhydrous ammonia or preemergence herbicides will need to think even harder before making a switch to soybeans, notes Nielsen. With anhydrous ammonia application costs ranging from $80 to $100/acre, much of the economic incentive to switch to soybeans is lost once nitrogen is put down, he explains. A previous corn herbicide application this season decreases the economic incentive to change crops even more, he adds.

Just like last year though, standing water may again drown corn planted ahead of heavy rains, points out Vince Davis, University of Illinois Extension soybean agronomist. In those situations, farmers may feel like their only choice is to replant soybeans, he says. Yet, that’s not always the case.

“Farmers will need to check their herbicide label first to see if they can switch to soybeans in a replanting situation,” advises Davis. “If you’ve already applied atrazine or an acetochlor-plus- atrazine product, then your replant option may be limited to either to corn or sorghum.”

Thus, a switch to soybeans is probably more likely in southern portions of Illinois, says Davis. “If there is a switch, it will likely be in the southern third of the state, which didn’t have as much chance to apply herbicides and anhydrous ammonia as the rest of the state.”

While much anxiety will remain until corn and soybean crops are planted, Davis advises farmers to avoid trying to push adverse planting conditions too far. “At least for soybeans, there’s still plenty of time to plant, so don’t risk mudding in your crop when conditions are too wet for field work,” he says. “You don’t want to make a bad situation even worse by causing compaction that could prevent seedling emergence and significantly lower yields.”

More information on optimal soybean planting dates for Illinois.
More information on late corn planting decisions for Indiana.