Monoammonium phosphate

MAP is produced by partially neutralising phosphoric acid with ammonia, yielding an acidic salt with a guaranteed analysis of roughly 11% nitrogen and 52% phosphorus (as P₂O₅). It contains no potassium.

Chemical formula

NH₄H₂PO₄

Nitrogen content

About 11% total nitrogen, as ammonium

Phosphorus content

About 52% P₂O₅, highly water-soluble

Granule reaction

Acidic zone forms around the dissolving granule

MAP supplies phosphorus, its dominant nutrient, in a highly water-soluble form, along with a smaller amount of nitrogen as ammonium. The phosphorus and nitrogen are released together as the granule dissolves in soil moisture.

• Phosphorus is the primary nutrient, at high concentration and full water solubility
• Nitrogen is supplied as ammonium, a secondary but useful contribution
• No potassium or micronutrients are supplied

MAP is widely used as a starter fertilizer placed near the seed or root zone at planting, where early phosphorus availability supports root establishment, and as a base material for compound fertilizer blends and soluble fertigation programs.

• High phosphorus concentration reduces bulk and handling cost per unit of nutrient
• Complete water solubility suits banded starter placement and fertigation
• Common building block for NPK blends and liquid fertilizer formulations

Phosphorus from MAP, as with other phosphate fertilizers, is most effective when placed close to developing roots, since phosphorus moves little in most soils. General practice accounts for soil phosphorus status and pH, both of which strongly affect phosphorus availability.

Phosphorus lost from fields, whether dissolved or attached to eroded soil particles, can contribute to the eutrophication of surface waters. Because phosphorus binds strongly to many soils, surface runoff and erosion, rather than leaching, are usually the main loss pathways of concern.