Mono ammonium phosphate (MAP) is a widely used source of phosphorus (P) and nitrogen (N). It’s made of two constituents common in the fertiliser industry and contains the most phosphorus of any common solid fertiliser.
MAP has been an important granular fertiliser for many years. It’s water-soluble and dissolves rapidly in adequately moist soil. Upon dissolution, the two basic components of the fertiliser separate again to release ammonium (NH₄⁺) and phosphate (H₂PO₄⁻), both of which plants rely on for healthy, sustained growth. The pH of the solution surrounding the granule is moderately acidic, making MAP an especially desirable fertiliser in neutral- and high-pH soils.
Granular MAP is applied in concentrated bands beneath the soil surface in proximity of growing roots or in surface bands. It is also commonly applied by spreading across the field and mixing into the surface soil with tillage.
MAP is a granulated, high analysis source of nitrogen and phosphorus for use at planting of cereals, grain legumes, oilseeds, cotton and a range of forage crops.
MAP has good storage and handling properties. Some of the chemical impurities (such as iron and aluminium) naturally serve as a conditioner to prevent caking.
As with all P fertilisers, appropriate management practices should be used to minimise any nutrient loss to surface or drainage water.