- FEMA Denies Aid To West For Explosion
- West Football Field Center Of Controversy
- West Explosion Victim Thanks Her Lifesavers
- ATF: West Explosion Cause Undetermined
- Crime Not Ruled Out In West Blast: Sources
- Willie Nelson Gives $120K For Explosion Relief
- Texas Firefighters Focused Concern On Toxic Gases
- After West Disaster, Little Discussion On Soil Issues
- West Plant Explosion Cause Announced Today
- Paramedic Who Responded To West Blast Charged
- Email: West EMT Dismissed 2 Days After Blast
- State Criminal Investigation Of West Explosion Begins
- Hours Adjusted For West Disaster Recovery Center
- West Fertilizer Plant Targeted By Thieves In Past
- Lawmakers Want Answers In West Explosion
- West Explosion Takes Center Stage At state Capitol
- Smoke From West Plant To Be Part Of The Investigation
- Hundreds Seek Help After West Plant Explosion
- 100 West Residents Still Waiting To Enter Homes
- Relatives Honor West First Responders In Video
- President Obama To West, Texas: 'You're Not Alone'
- Fathers, Firefighters: Lives Lost In West, Texas
- Marathon Runner Witnesses Boston, Texas Disasters
- Westboro Church Plans To Protest West Funeral
- Students help West survivors
- President Obama Going To Service For West Explosion Victims
- School Underway In Tiny Texas Town Hit By Blast
- 4 More First Responders Killed In West Blast ID'd
- West Residents Back In Homes
- Federal Lawmakers Inspect Scene Of Blast In West
- 12 Dead, 200 Injured In West Explosion
- Search On For Those Missing In West
- West Pulling Together As A Community
- How To Help: West, Texas Emergency Resources
- West Man A Humble Hero
- West's Worse Fear Comes True
- Texas Mobilizes To Help West
- West Residents Face Death, Destruction After Explosion
- Perry: Nightmare Scenario After West Explosion
- Federal Investigators To Probe West Plant Blast Cause
- West Fertilizer Plant Cited For '06 Permit Violation
- Pope Francis Tweets Prayers For Texas Explosion Victims
- Texas National Guard At Site Of West Plant Blast
- West Fertilizer Plant Cited in 2006
- Texas Environmental Agency Monitoring West
- Statement From The President On Explosion In West
- West Explosion Kills Up To 15
- Another Deadly Texas Blast 66 Years Ago
- Willie Nelson Sends Prayer Tweet After West Blast
- Multiple Deaths Reported After Waco-Area Fertilizer Plant Explosion
- Some Firefighters Unaccounted For After West Blast
- Police: 5 To 15 People Killed In West Explosion
After West Disaster, Little Discussion On Soil Issues
Updated: Thursday, May 16 2013, 10:33 AM CDT
As the catastrophic fertilizer plant explosion in West continues to elicit debate about regulation, one factor that hasn't been discussed as much is the soil of Central Texas.
Texas diverse geology and soil compositions have led to an equally diverse system of fertilizer distribution. Each type of fertilizer has different uses and risks some work better on particular crops and soils than others.
According to Mark L. McFarland, a soil fertility specialist at Texas A&M University, there are five different agricultural fertilizers widely used in Texas. Ammonium nitrate was stored in large quantities at a depot in West that exploded last month, killing at least 14 people and injuring hundreds more. The other types used in the state include anhydrous ammonia, urea, ammonium sulfate, and a liquid solution of urea and ammonium nitrate, often called UAN.
Much of the soil in Central Texas, where many farmers got their fertilizer from the West plant, is alkaline. That attribute is related to the large amount of calcium carbonate the chief component of limestone in the region's geology.
Alkaline soils exacerbate the problem of fertilizer evaporation. Farmers tilling alkaline face decreased returns from using liquid fertilizer.
"Dry, straight ammonium nitrate has an extremely low volatility risk on any soil," McFarland said, referring to the fertilizers low evaporation rates. In addition, ammonium nitrate has high levels of nitrogen, which along with ammonia is critical for plant growth, and is ideal for growing grain.
While anhydrous ammonia, a gas, is the cheapest and easiest fertilizer to produce, it must be injected into soil using specialized equipment, or else much of the benefit is lost. The gas poses a combustion risk if subjected to a heat source. But according to the most recent reports, the substance, held at Adair Grain Co.s facility in West, didn't contribute to the blast and tanks holding it remained intact even after the explosion.
The other four types of fertilizer are deployed in either liquid or powder form. Urea is a good source of nitrogen, but its nutrients evaporate at a high rate. It poses a moderate combustion risk, depending greatly on how it's stored.
The largest stockpile of any type of ammonium nitrate combination in the state, as reported to the Department of State Health Services, is a depot northeastern Amarillo depot owned by Gavilon, an Omaha-based company. The facility reported holding more than 2.1 million pounds of such a liquid UAN solution on an average day in 2012.
Holding these volatile chemicals in a liquid solution almost eliminates the risk of a catastrophic explosion. But that safety comes with a trade-off: UAN volatilizes faster than pure ammonium nitrate. Improperly applied, farmers lose some of the benefit of the fertilizer.
The fertilizer that poses the smallest risk of evaporation, and is the easiest to apply, also happens to be the most dangerous: powdered ammonium nitrate.
But the attribute that makes it versatile its powdered form also makes it dangerous. Ammonium nitrate was responsible for the largest non-nuclear explosion to take place on American soil: the Texas City Disaster of 1947.
More than 7,700 tons of the powder exploded, killing 581 people and injuring thousands. ¨It was also the primary chemical used in the 1994 Oklahoma City bombing.
In recent years, ammonium nitrate has become harder for farmers to get, partially as a result of the safety and security practices mandated by the federal government after the Oklahoma City bombing and 9/11.
The Department of Homeland Security requires depots that hold large amounts of high-risk chemicals to report their stockpiles to DHS. Under new rules, facilities that hold large amounts must make security improvements, including security camera coverage and perimeter fencing, which sometimes proves too expensive for smaller operators.¨
Charles C. Mitchell Jr., an extension agronomist and professor of soil sciences at Auburn University, says he was surprised to hear that there were facilities in Texas holding substantial amounts of ammonium nitrate.
Ammonium nitrate has pretty much become impossible to get in Alabama, because of all the regulations, he said. I was surprised they were still storing it and using it in West.
As restrictions on the use and storage of ammonium nitrate have increased nationwide, some smaller dealers have stopped selling the fertilizer. Ammonium nitrate is easier to obtain in Texas in part because larger companies, better able to handle the costs regarding safety and security improvements, play a role in the state's diverse fertilizer distribution network, Mitchell says.
But the overall decrease of availability in ammonium nitrate poses risks for Hill Country farmers, who may find it harder to get the fertilizer best-suited for their needs.
This article originally appeared in The Texas Tribune at http://www.texastribune.org/2013/05/15/fertilizer-story/.