Molecule of the Day

Plants need nitrogen. You’re soaking in it – the air is 78% N2 Trouble is, the kind of nitrogen plants need is reduced (i.e., has more electrons) relative to dinitrogen in the air. In the past, this meant rotating crops – peanuts, for example, promote nitrogen-reducing, or “nitrogen-fixing” bacteria.

We learned some time ago, though, that we could fix our own nitrogen. The Haber-Bosch process can take dinitrogen and dihydrogen and produce significant amounts of ammonia – “fixed” or reduced nitrogen. You can use ammonia as a fertilizer – if you keep it in big tanks like you use for BBQ propane, you can keep liquid ammonia around (it boils well below zero). If you mix ammonia with nitric acid, you can make ammonium nitrate, an easy-to-handle solid:


Problem is, nitrate is a pretty good oxidizer, and you’ve got all that reduced nitrogen around to react with it. Ammonium nitrate is actually a pretty good explosive, and it’s even better when you have some more fuel around – like diesel. Ammonium nitrate/fuel oil, or ANFO, was used by American terrorist Timothy McVeigh on his attack on the Oklahoma City Federal Building.

The fact that fertilizer, which is ubiquitous, contains a potential explosive component, is the subject of much consternation. Tomorrow, a proposed solution.


  1. #1 Dunc
    September 24, 2008

    Would I be correct in thinking that it was initially produced as an explosive, and only subsequently used as a fertiliser?

  2. #2 locklin
    September 24, 2008

    Too bad there’s not really much need for ammonium nitrate. I worked in a farm coop for a year and the couple skids of ammonium nitrate sat and collected dust the whole time. Farmers generally have ammonia applied as a service, or purchase dry fertilizer based on Urea.

  3. #3 Uncle Al
    September 24, 2008

    Ammonium nitrate is a pussycat unless contaminated with chloride (NH4NO3, NH4Cl, Zn dust, mix, add drop of water). Adding diesel doesn’t make much of an boom unless you are very good at it (glass microballons included).

    McVeigh’s explosion was wholly remarkable for there having been been no NOx plume. Somebody is lying.

  4. #4 caglar keskin
    April 30, 2010

    I am a farmer and growing vegetables to sell. For more efficency i use fertilizers but while using them it is important to
    keep it healthy because some fertilizers contain corruptive elements so i try to read everything about fertilizers and try
    to keep my product healthy. I am grateful for those who gives information about fertilizers and anyone who
    uses fertliziers should read about it, i also found another good guide which should be read too i think;

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