Some areas of Iowa have recently received heavy rainfall, resulting in soils saturated or with standing water. Following are excerpts from an article published in 2011 when similar conditions occurred. The early spring 2014 season was on the cold side, so conversion of ammonium fertilizers to nitrate should have been slower than normal. This could be helpful for avoidance of nitrate losses, as would recent sidedress application of ammonium-containing fertilizers. However, wet soils in June are much more conducive to nitrate loss (compared to early spring) as soils are warm and, with prolonged saturation and tile flow, losses mount. Remember, ammonium is held on the soil exchange complex, but nitrate can leach or be denitrified to nitrogen (N) gasses. Also remember that corn plants do not respond well to saturated soils, and therefore can express symptoms similar to N deficiency when they really are showing excess water stress.
Iowa State University
Sawyer, John E., "Estimating Nitrogen Losses in Wet Corn Fields" (2014). Integrated Crop Management News. 852.