There are many other ways to lower Ph, like many kinds of acid.
As for making a bomb, it's ammonium nitrate with diesel, - most explosive contractors use that along with dynamite. You have to know the mixing procedure though.
The hollywood explosive is also a lot of ammonium nitrate mixed with dynamite. The reason is price and availability.
N fertilizer contains a certain amount of calcium, to make it less explosive.
N fertilizer on it's own will lower Ph, but lots of N will also kill fish - both are problems in intensive agriculture.
(N Fertilizer is Calcium ammonium nitrate, typically containing somewhere between 27 and 33% of pure N, with some typical 2-4% Ca)