Complex sentence: In contrast to ammonium sulfate, ammonium nitrate is strongly hygroscopic, so the mixture of ammonium sulfate and nitrate clogged together under the pressure of its own weight, turning it into a plaster-like substance in the 20m high silo.
Split into simpler sentences: In contrast to ammonium sulfate, ammonium nitrate is strongly hygroscopic so that the mixture of ammonium sulfate and nitrate clogged together under the pressure of its own weight. This turned it into a plaster-like substance in the 20 m high silo.