Arkansas hay and vegetable producers may be losing a favored fertilizer over concerns that it can be used to make explosives, according to Extension experts with the University of Arkansas Division of Agriculture.

A law passed last year allows the Department of Homeland Security to regulate the sale and storage of ammonium nitrate and certain other chemicals, keeping them out of the hands of terrorists while allowing them to be available for agricultural use.

Arkansas farmers and ranchers used more than a million tons of fertilizer in 2007 including 50,000 tons of ammonium nitrate, said Leo Espinoza, an Extension soil scientist.

The law requires fertilizer dealers and storage facilities to have plans to protect their fertilizer stores. However, “the handling regulations are complicated. And to bring some of the existing facilities to compliance, will require a significant investment, so many dealers will just stop selling ammonium nitrate,” Espinoza said.

Many dealers and hay producers are switching over to non-regulated fertilizers: calcium ammonium nitrate and urea, a favorite of row crop producers.

“The problem is calcium ammonium nitrate has a little less nitrogen content than ammonium nitrate, and it costs a little bit more,” Espinoza said.

John Jennings, Extension forages professor, said some dealers are still trying to carry ammonium nitrate, particularly in northwestern Arkansas where most beef production is located, but some of them are finding that regulations and other issues are making it increasingly difficult.

“Some dealers and producers are looking at the other alternative sources,” he said. “Urea is cheaper per pound of nitrogen and, in the spring, just as efficient. In the summer, it can volatilize during hot weather.

“All the sources are higher than ammonium nitrate except for urea, and it's cheaper right now. In cooler weather, it would be the best source to go with, by far, if dealers carry it,” Jennings said.

Most dealers carry either urea or ammonium nitrate, but not both.

If dealers aren't used to carrying urea, then they may switch to ammonium sulfate or calcium ammonium nitrate, if they can get it,” he said. “But the calcium ammonium nitrate supply isn't good. It's a safer, good quality product, it's just really expensive because it's imported from Europe.”

Jennings said new products are coming out all the time. He urged producers to compare the price of nitrogen fertilizers by the pound of actual nutrients in the product instead of by the ton.

Espinoza said hay producers like to use ammonium nitrate because it can sit on the ground for longer periods of time waiting for rain to move it down into the soil. “Urea needs to be incorporated into the soil (by cultivation or rain) within about five to seven days. If that doesn't happen, it starts to break down and the risk of volatilization losses increase.”

Espinoza said the Division of Agriculture is collaborating with county agents on a study to devise alternatives.

“We already have some answers,” he said. “There are some additives in the market such as Agrotain that can extend the time urea can sit in the ground by two to three days, before it starts volatilizing. Hopefully, that's enough time for rain to come.” However, last year we had dry spells that lasted up to three weeks. Under those conditions there is little you can do.”

Regardless of the nitrate source, all fertilizers need water to activate them and get them moving into the subsoil.

For more information about fertilizers, contact your county Extension agent. The Cooperative Extension Service is part of the U of A Division of Agriculture.