For it to explode you need ammonium nitrate with a minimum of 32% nitrogen, no phosphate or potash. Most fertilizer is "prilled" that is pelletized and then coated with clay. This prevents the ammonium nitrate (hygroscopic) from absorbing moisture from the air and caking into a solid mass. It also acts as a "time release" for the fertilizer that helps prevent burning the plants. When ammonium nitrate is prilled it also fails to absorb diesel fuel and thus it is useless as an explosive. It is possible to remove the clay by dissolving the ammonium nitrate in absolute alcohol, separating and then evaporating the solvent but that is a process you might use for ounces not hundreds of pounds.
The short of it; news article is BravoSierra!
Regards,
GtG
dissolving the ammonium nitrate in absolute alcohol, separating and then evaporating the solvent... Now if you could lay your hands on some anhydrous hydrazine, and used that instead, you could filter out the clay and use the finished liquid product directly. This would be "Astro-Lite" the most powerful non nuclear explosive available.
Beware of the fumes when mixing the ammonium nitrate and the anhydrous hydrazine, the gas can kill you.
So endith todays lesson.
Regards,
GtG