Every year, agronomists from the University of Kentucky College of Agriculture do field work to examine their recommended nitrogen application rates so they can provide up-to-date information to producers.

"Our larger effort is to make sure that as varieties and practices change, we consider whether nitrogen levels need to change," said John Grove, UK Extension agronomist.

His nitrogen trials for corn production are on four sites this year, located in Henderson County, Hardin County, Breathitt County and the UK Research and Education Center in Princeton.

"We are directly looking at the question of what are the most economically optimum rates of N fertilizer," Grove said.

Lloyd Murdock, UK Extension agronomist, said it is also important that the university's rate recommendations be environmentally sound. Universities will be looked to for their recommendations as national and state nutrient management plans come into effect.

Interest in nitrogen rates was particularly high this year because of the high price of that fertilizer. Nitrogen is the No. 1 input farmers put on corn that can impact yield. It is the main input overall, behind sunlight and water, Grove said.

With rapid fire advances in genetics, varieties continuously change. Grove said that also creates a need for ongoing research and so do management changes, such as site- specific soil management (precision agriculture). Generally, these changes have had little impact on recommendations, but occasionally something reacts differently and farmers need to know this , he said.

Currently, UK's nitrogen rates are based, in part, on soil drainage capability. The recommendations are outlined in AGR-1, an Agronomy Department publication. Typically the recommendations run between 125 to 225 pounds per acre.

The recommended N rates are based on replicated field research trials conducted over many years at many different locations in Kentucky and are adequate for most soils and seasons, Grove said. Rates recommended for corn have changed little in recent years while recommendations for other crops, such as wheat, have been tweaked.

Grove said he is looking at the recommendations for some well drained soils to see if the low end recommendation is too low. All Grove's nitrogen work this year is in small plots not large field trials. In this year's plots, test rates go to 300 pounds per acre and beyond.

"I can spend a little money in small plots and perhaps save growers a lot of money," he said.