Rodney,
Your are mixing terms to the point of being nonsensical. Ammonium
Nitrate is just that, Ammonium (NH4) + Nitrate(NO3). Conscientious
fertilizer dealers often don't sell it to just anyone because it is the
stuff that was the primary ingredient for blowing up the Federal Courts
Building in Oklahoma City. Uniform delivery people can be too terrified to
have it in their truck - I had it delivered once and the driver was relieved
that it hadn't blown up yet - telling him that it needed another ingredient
AND dynamite to set it off failed to quell his fear.
Anyway, if you are fertilizing with any form of nitrate, adding just a
smidgeon too much can burn your plants just as fast as urea will. Ammonium
is best because it is not available to plants until after soil bacteria
convert ammonium to nitrate. Soil bacteria provide a slow release of
nitrate which is unlikely to ever burn plants.
I wonder what the tomatoes would have tasted like had they used ammonium
nitrate to fertilize them. I say this with tongue in cheek because ammonium
nitrate has both names in it's name. I have to assume that "ammonium" is
ammonium hydroxide (a more dangerous, for the handler, and expensive
chemical than ammonium nitrate), although it could possibly be urea as it is
a commonly used fertilizer also. I have never purchased or ordered ammonium
via mail order but I suppose it can be acquired that way, but when I
google - ammonium mail order - I find lots of ammoniums that can be
ordered mail order; Ammonium Lactate, Ammonium Molybdate, Ammonium
Thiocyanate, Ammonium Carbonate, Ammonium Chloride, Glufosinate Ammonium,
ammonium hydrogen hemihydrate, ammonia (ammonium hydroxide diluted in
water), ammonium bicarbonate, ammonium nitrate, ammonium hydroxide, and
more, but I really have no idea just which ammonium the Brits were using.
Can I run down to the nearest nursery and order some ammonium? What
chemical do you think those researchers were using?