MAP (monoammonium phosphate)

Monoammonium phosphate (MAP) is an NP compound fertiliser obtained from the neutralisation of phosphoric acid with ammonia. Its chemical formula is NH4H2PO4. Common grades show 11 % nitrogen (N) and 52 % diphosphorus pentoxide (P2O5)^[1]. A variant at 12 % N and 61 % P2O5 is listed with full water solubility (100 % ws1)^[2]. MAP differs from DAP (diammonium phosphate) through a lower N/P2O5 ratio, making it suitable for situations where phosphorus is the limiting factor.

Manufacture

MAP production forms part of the standard phosphate route: phosphate rock is attacked by sulphuric acid to produce phosphoric acid via the wet process, which is then neutralised with ammonia^[3][4][5]. This ammoniation stage can proceed through several technical configurations. The direct neutralisation process in a pipe reactor harnesses the heat of reaction to evaporate water present in the phosphoric acid, allowing low recycle rates and reduced utility consumption^[6]. Conventional pre-neutralisation, carried out in a series of tanks, yields a more aqueous slurry, resulting in high recycle rates and greater energy use, though with satisfactory final product quality^[6]. The pipe reactor may be integrated into the granulation drum, or even supplemented by a second unit in the dryer^[6].

Agronomic uses

MAP is employed as a base fertiliser or placed with the seed, owing to its high phosphorus concentration and good water solubility. Its 11-52-0 formula makes it the product of choice for high phosphorus requirements, particularly during the early growth stages of crops. Within fertiliser programmes, it also serves as a raw material in the formulation of NPK fertilisers and bulk blends^[1][3]. In the United States, ammonium phosphates (DAP/MAP combined) account for 4 % of nitrogen fertiliser application, well behind urea (24 %), direct application ammonia (27 %), UAN solutions (26 %) and nitrates (2 %)^[7]. In Brazil, this same category reaches 5 % of nitrogen application, with urea dominating at 56 %^[8].

Market and trade

MAP ranks among the three main finished products of the phosphate sector, alongside DAP and TSP (triple superphosphate)^[3][4]. In 2023, world MAP production stood at 35 Mt (million tonnes of product), of which 16 Mt was exported^[4]. For comparison, DAP production reached 85 Mt (8 Mt exported) and TSP production 30 Mt (12 Mt exported) in the same year^[4].

MAP trade flows are shaped by the geography of phosphate resources and ammonia capacity. The United States uses imported ammonia to produce DAP and MAP^[9]. Morocco, holder of the world's largest phosphate reserves, likewise imports ammonia for this same production^[9]. The Middle East constitutes a significant exporting region for ammonium phosphates and other fertilisers^[10]. Tensions in the Strait of Hormuz in early 2025 illustrated the vulnerability of these flows, with 150,000 tonnes of phosphate fertilisers blocked on three vessels west of the strait in late April^[11].

Prices and costs

MAP pricing is closely tied to that of its feedstocks, phosphoric acid and ammonia, as well as to seaborne freight. The BPL (bone phosphate of lime) reference for phosphate rock and sulphuric acid costs feed into upstream pricing^[3][4]. FOB and CFR price bases structure international transactions [wiki:bases-de-prix-fob-cfr-fca]. The P2O5 concentration of MAP (52 %) marginally exceeds that of DAP (46 %), which may lower transport cost per nutrient unit over long distances.

Regulation and environment

MAP production falls under industrial regulations applicable to phosphate fertilisers, notably regarding atmospheric emissions and residue management. Phosphogypsum, a by-product of wet-process phosphoric acid manufacture, represents the main waste management challenge for the sector. In the European Union, the fertilising products regulation governs cadmium and other contaminant levels. International transport of phosphate fertilisers falls under the IMDG (International Maritime Dangerous Goods) Code, referenced in industry technical glossaries^[12].