Cornfield in southern Iowa.

It’s been a challenging growing season for farmers in many parts of Iowa, for a variety of reasons.

In north-central Iowa, crops were planted late due to snow and persistent heavy rains this summer caused ponding and drowned-out spots in many fields. But Brent Renner, who’s farms near Klemme, says much of the corn that survived is looking good.

“I’ve been through some stuff that at least appears to still have 240-bushel potential,” Renner says. “But there are very few, if any, fields in my immediate area that are going to have overall farm averages at that level.” Kent Klingbeil, an agronomist with Ames-based Landus Coop, says his biggest concern is nitrogen stress in corn.

“I’ve been out in some fields and there are a lot of leaves firing up on the bottom with nitrogen deficiencies,” Klingbeil said. “It will be interesting to see if we can mineralize enough nitrogen to keep filling those ears or if we’re going to run a little short.” Renner, who’s a custom sprayer, says weed control has also been a challenge. He says herbicide spraying programs have been “turned upside down” by the spring they had in north-central Iowa.

Many farmers in central and southern Iowa have crops that were damaged in the tornado outbreak one week ago. Other farmers, in south-central and southeast Iowa, are having problems with drought. But statewide, this week’s U.S.D.A. report rated 79% of Iowa’s corn crop in good-to-excellent condition and 76% of the state’s soybean crop in the good-to-excellent category.