Ammophos (monoammonium phosphate or MAP) 12:52 – concentrated complex phosphate-nitrogen fertilizer. It’s obtained by neutralizing orthophosphoric acid with ammonia. It mainly consists of monoammonium phosphate NH4H2PO4 and partially diammonium phosphate (NH4)2HPO4. Ammophos is a highly concentrated fertilizer containing nitrogen and phosphorus in a well-assimilated form. 100 kg of ammophos replaces at least 250 kg of simple superphosphate and 35 kg of ammonium nitrate. The ratio of components in ammophos 12:52 is considered standard and most effective. Despite the fact that there is a small amount of nitrogen in the fertilizer, it is one of the most important and economically profitable fertilizing.
Ammophos is low-digestible and belongs to the group of hardly soluble phosphate fertilizers. These compounds, which do not dissolve in water, are very poorly soluble in weak acids and completely dissolved only in sulfuric or nitric acid (strong acids). Difficult soluble compounds are used exclusively on acidic soils. Insertion of this fertilizer into the soil made in advance, mixing well than plants absorb phosphorus in this case only after its reaction with acid from the soil. If ammophos inserted in advance in large doses it will help plants for several consecutive years on which water-soluble compounds are incapable. Difficult soluble fertilizers should be applied as deep as possible into the soil, closer to the roots of crops since they can’t penetrate with water into the lower layers independently.
The disadvantage of ammophos is that it contains much less nitrogen than phosphorus, whereas in practice they are most often applied in equal doses. Therefore, to obtain a normal ratio of N and P2O5 to ammophos it’s necessary to add a certain amount of one-way nitrogen fertilizer – NH4NO3 or CO(NH2)2. When these fertilizers are applied before sowing under cotton and winter crops they can be used without addition of nitrogen fertilizers since in this case the lack of nitrogen is compensated by the introduction of nitrogen fertilizers into top-dressing.