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Serving: IA

Agronomists Caution About Switching Maturities

ISU specialists advise farmers to stick to original corn and soybean planting plans.

Sunny weather this past week helped dry out the saturated and flooded fields in Iowa so farmers could get back in the field to plant corn and soybeans.

Iowa State University Extension agronomists are advising producers not to go switching hybrids and varieties of corn and soybeans just yet. "There is no need to think about changing hybrids until the end of the month. Hybrids easily adjust to these later planting dates," says Roger Elmore, ISU Extension corn agronomist. "Yield potential for corn doesn't decline until around May 15 or so. There is no need to get too concerned about late planting yet."

Elmore has more information on this topic on his Web page  

What about soybean planting dates?

"We still have several weeks left for planting soybeans," says Palle Pedersen, ISU Extension soybean agronomist. "The same recommendations exist for the growers whether it is the last week of April or the last week of May."

Pedersen encourages farmers not to switch soybean varieties to a shorter maturity group yet, since full season soybean varieties can be used through the first week of June without problems. More information on soybean production and recommendations for Iowa can be found at his Web page

The saturated and flooded crop plan may have an impact on nitrogen (N) for this season's corn crop, says John Sawyer, ISU Extension soil fertility expert. He says having the wet conditions occur in the early spring is helpful as soils are cooler, so less fertilizer is converted to nitrate, and losses by denitrification in flooded fields are slower.

Nitrogen losses are occurring

"Losses of nitrogen are occurring," he says. "The best course of action now is to wait, get the crops planted and then use tools like loss estimation, soil nitrate testing and corn plant N stress monitoring to check on the N status and determine if additional N is needed. Rushing out to apply more N could put that N at risk if we get more wet conditions. For now, follow your intended planting plan as best you can," he says.

Sawyer points out that you can make a sidedress application of nitrogen to corn, if the results of the late spring soil nitrate test indicate you need to apply more N to keep the crop from running short and hurting yield potential significantly.

Sawyer is telling crop advisers and farmers dealing with nitrogen issues on flooded cropland to check past newsletter articles posted on the ISU Extension soil fertility Web page at: New articles dealing with the wet conditions will be posted there also.

The ISU Integrated Crop Management Newsletter is another source for current crop recommendations from ISU Extension. The newsletter is issued weekly during the crop season and can be viewed at

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