Anhydrous Ammonia Can Be Used To Grow Crops Or Manufacture Methamphetamines. As farmers prepare their fields for planting this month, officials say they should keep a watchful eye on their fertilizer. Farmers and supply distributors are experiencing rampant theft of anhydrous ammonia, a substance normally used as a nitrogen fertilizer, according to a press release from MU's Extension Office. Anhydrous ammonia is the only key ingredient in illegal methamphetamines that can't be bought in grocery stores. The rise in theft reflects Missouri's status as the country's meth leader in meth raids and seizures for the second year in a row, according to the release. [continues 621 words]