Factbox - Anhydrous ammonia production and uses

(Reuters) - The fertilizer plant that exploded on Wednesday night in West, Texas, had tanks of anhydrous ammonia on site.

Following are facts about the production and use of the fertilizer.

* Farmers use anhydrous ammonia as a fertilizer to boost nitrogen levels in the soil and increase corn production. Here are some facts about anhydrous ammonia.

* U.S. production of anhydrous ammonia in 2011, the latest year for which data was available, was 9.35 million tonnes, according to the U.S. Geological Survey's minerals yearbook.

* Domestic production capacity in 2011 was 12.9 million tonnes.

* The U.S. imported another 5.6 million tonnes in 2011.

* The biggest U.S. domestic production plant, with an annual capacity of 2.49 million tonnes was owned by CF Industries Holdings and located in Donaldsonville, Louisiana.

* Other U.S. producers include Agrium Inc, Dakota Gasification Co., Honeywell International Inc, Koch Nitrogen and PCS Nitrogen Inc.

* Domestic anhydrous ammonia stocks at the end of 2011 were 178,000 tonnes, up 8 percent from the end of 2010.

* 87 percent of anhydrous ammonia is used as fertilizer, with the remaining 13 percent used in chemical and industrial sectors.

* Fertilizer is the biggest item other than land in an annual budget for farmers, averaging between $129 and $170 per acre in Illinois in 2013.

* An estimated 6,500 farm retail stores in the United States blend, store or sell fertilizers to farmers.

* Growers often apply the anhydrous ammonia to fields the plan to seed with corn during the spring in the fall but some will put it on during the spring just before planting.

(Reporting by Mark Weinraub; Editing by Bob Burgdorfer)