May 3, 2006 | By: Terri McLean

Corn, forage and tobacco growers accustomed to using ammonium nitrate fertilizer as their primary source of nitrogen might want to consider an alternative to help reduce overall production costs.

Greg Schwab, Extension soil management specialist with the University of Kentucky College of Agriculture, said homeland security concerns surrounding ammonium nitrate have led to reduced availability and, therefore, higher prices when compared to other nitrogen sources.

“Ammonium nitrate can be used to make a bomb,” he said. “That is just what happened in Oklahoma City, and there are concerns that this might happen again, but on a much larger scale.”

Those concerns have prompted the nation’s lawmakers to consider legislation regulating ammonium nitrate fertilizer, including requiring buyers and sellers to register with the Department of Homeland Security, Schwab said. Under the proposed legislation, anyone who violates the act will be subject to a fine of up to $50,000 per occurrence.

“In reality, this new legislation is added paperwork and liability that most retailers think is not worth the time, trouble or potential fines,” he said. “For these reasons, many fertilizer distributors are choosing not to handle this product.”

That is particularly problematic for farmers in central and eastern Kentucky, where ammonium nitrate is more commonly used. 

“The lack of availability is a big deal because many of these farmers have used ammonium nitrate for so long,” he said.

The “logical substitute” for ammonium nitrate fertilizer is urea. But urea is more difficult to manage because, unlike ammonium nitrate, urea applied to the soil surface can be lost through a process called volatilization. Depending on weather conditions, volatilization losses can be as high as 2 to 3 percent of the application per day.

“Understanding these weather conditions is a key to managing urea fertilizer,” Schwab said. “For surface-applied urea, maximum volatilization losses occur when the soil is warm and wet, followed by an extended drying period.”

Volatilization losses stop after the fertilizer is washed into the soil, but “timing is often easier said than done,” Schwab said. Another option is to use a urease inhibitor, which prevents volatilization for seven to 15 days, depending on the rate applied.

A longer term option to lessen volatilization is to switch to a liquid fertilizer that can be injected into the soil with little surface disturbance, he said.

Despite farmers’ reluctance to use urea in the past, many are now considering its use. “It is the only nitrogen source that is practical in many areas of Kentucky,” Schwab said.

For addition information regarding nitrogen management, contact your county Extension office.


Greg Schwab, (859) 257-9780