Iowa farmers say they’re finding good corn and soybean yields this fall, although there is a high degree of variability brought on by excessive rainfall and other weather challenges during the 2014 growing season.

After a slow start to harvest, farmers said several days of favorable weather allowed them to bring in most of their soybean crop and make good progress on corn by the end of last week. The week began with the state’s soybean harvest nine days behind the normal...