Rainfall records were washed away in dozens of Iowa locations last month, and many farmers are worried that their fall-applied nitrogen (N) went down the river along with the excess moisture.

That may not be the case, depending on how and when nitrogen was applied, according to Iowa State University Extension soil fertility and nutrient management specialist John Sawyer.

"It is quite hard to make an estimate of losses for such an extreme event and time of the year. (Farmers)...