This summer, farmers and ranchers will find it harder and harder to buy ammonium nitrate, a commonly used nitrogen fertilizer, said a Texas Cooperative Extension expert.

Past concerns with nitrogen fertilizer have been linked to the cost of oil and natural gas. This time the shortage has nothing to do with fuel costs, but has originated from fears of terrorism. Ammonium nitrate can be used to make bombs such as the one that destroyed the Alfred P. Murrah Federal Building in Oklahoma City in 1995.

And federal regulations may soon make it just too much trouble for fertilizer dealers to stock and sell the product.

Several legislative attempts to regulated and record the sale of ammonium nitrate have failed since the Oklahoma City bombing, said Roger Hoestenbach, associate director of the Texas Feed and Fertilizer Control Service in College Station. But legislators included extensive record-keeping requirements for dealers of ammonium nitrate in the 2007 federal farm bill.

Feed and fertilizer dealers are responding to the requirements, which go into effect in October, by reducing stocks of ammonium nitrate, and perhaps not carrying it at all, Hoestenback said.

“I believe that the trend will be not to carry it all,” said Douglas Steele, owner and manager of Steele’s Feed and Fertilizer in Troup, a rural Smith County community.

But Steele said it’s not the record keeping that will discourage his keeping ammonium nitrate on hand, it’s his insurance company.

Hoestenbach agreed. Insurance companies are getting “nervous” about litigation involved with ammonium nitrate, where fertilizer used for a terrorist bomb could be traced back to the dealer, he said. No matter if the dealer had good reason to believe the sale was for agricultural purposes, the dealer and his insurance company could still be sued, he said.

”It’s similar to the argument that if you’ve got a swimming pool in your back yard and you don’t have it fenced, and someone falls in and drowns, then you should have known better,” Hoestenbach said.

It’s a result of living in an increasingly “litigable” society, he said. Without ammonium nitrate, east Texas producers are left with two choices for supplemental nitrogen: urea or ammonium sulfate, said Joe Vendramini, Extension forage specialist.

Ammonium sulfate fertilizers tend to increase soil acidity. With most East Texas soils already acidic, the use of ammonium sulfate would require extra liming in most cases, and would not be the best option, Vendramini said.

Urea is a better choice for most east Texas fields, but it also has a drawback; volatility, its tendency to readily evaporate under warm, wet conditions, he said.

On the plus side, urea has historically been one of the cheaper nitrogen fertilizers from the standpoint of actual cost per pound of nitrogen, Vendramini said. Where ammonium nitrate is about 34 percent nitrogen per weight, urea is about 46 percent nitrogen per weight.

For producers, this cost difference is offset, though, by the chances a high percentage of urea nitrogen will be lost through volatilization.

”The worst thing they can do is apply urea when there’s been a heavy dew followed by a warm day,” Vendramini said. “Loss to volatilization could be considerable.”

The best situation is applying urea on dry soils shortly before a good rain. Losses to volatilization would be decreased in such a situation, he said.