Today’s corn hybrids are far more efficient users of nitrogen than their counterparts from five decades ago, according to a two-year Iowa State University (ISU) study.

That’s good news for farmers on the economic and environmental front, says ISU Extension fertility specialist John Sawyer. While corn yields have increased by an average of nearly 2 bushels per year during the past half-century, optimum nitrogen rates have remained mostly un­­changed since that time, he reports.

“The current suggested rates are within the same range as they were in the 1970s despite the big yield increase in corn,” Sawyer says. “(Farmers) have not really had to dramatically raise N rates to increase yields.”

A two-year hybrid era study near Ames compared corn hy­­brids over five decades from 1960 to 2000. All of the hybrids...