I understand there are truckloads of it shipped around in agricultural areas for fertilizer and I believe also for killing weeds or something.
Fertilizer yes, several different forms, gas stored under pressure as a liquid (anhydrous ammonia), liquid (28% and 32%) and dry.
AMS (Ammonia Sulfate) is used as a water conditioner with certain herbicides, it helps condition hard water. Softer water makes a lot of herbicides, like glyphosate work better. Side effect, too much AMS and you can burn the leaves of the plants you aren't trying to kill.