Solid ammonium nitrate (NH4NO3) is widely used in explosives and fertilizers. Since one of these products should explode and the other should not decompose in an uncontrolled way, research done in other industries has been interested in how this compound can best be produced, handled, stored, and finally used. The topics discussed in this book include the crystal structure, polymorphism and thermal behavior of ammonium nitrate; the phase transition of NH4NO3; the uptake, metabolism, toxicity, and effect of different nitrogen forms on growth in horticultural plants; and finally, the synthesis, chemical properties, health hazards and applications of NH4NO3.