Anhydrous ammonia is a relatively cheap fertilizer, and dry fertilizer was a longtime standard, but nowadays Central Texas farmers are more likely to use liquid fertilizer for a variety of reasons.I wondered why they would have that much ammonium nitrate around. Pasture fertilizer makes sense for Texas. Not that it might not be better to go another route, like encapsulated urea, but that would be more expensive. Safety-wise, it is a no-brainer.
Thin, coarse soil, especially in the Hill Country, works against anhydrous ammonia, a fertilizer that can escape through the soil in its gaseous state, according to Jimmy Duecker, owner of Allied Agricultural Services in Stonewall.
And then there’s the safety issue. Liquid fertilizer typically contains ammonium nitrate but in a nonvolatile form.
“I won’t use it,” Duecker said of the anhydrous ammonia and the ammonium nitrate because of the safety and permitting issues. “You can weld on one of my tanks” — which he said store a different type of liquid fertilizer — “and it won’t explode.”
Liquid fertilizer has become common, said Benton Floerke, owner of Agro-Tech Service of Lampasas, a fertilizer mixing and sales company, because “it’s so much easier to handle because of the safety and flexibility of the liquid.”
Though ammonium nitrate might have been a culprit in the West blast, it’s a common fertilizer ingredient, especially in areas where pastureland is common, said Tim Herrman, the Texas State chemist, whose office tracks fertilizer storage.
The chemical is useful because it doesn’t break down as quickly as other fertilizers. That’s handy if, say, a farmer spreads the fertilizer anticipating a rainfall to carry it into the soil, but then it remains dry. Ammonium nitrate would hold for a while longer where other fertilizers would break down, Herrman said.
Yet ammonium nitrate also can be used in the manufacture of bombs, such as the explosives used by Timothy McVeigh to blow up the Murrah Building in Oklahoma City in 1995. For that reason, it is more tightly regulated than other farm chemicals — though as a security threat, not as an unusually unstable chemical.
Sunday, April 21, 2013
More On Fertilizer Safety and Use