Monoammonium phosphate is the salt NH4H2PO4. Soluble technical grade is sold as 12-61-0, which works out to about 12% N, all ammonium, and 26.6% elemental P. Cheaper granular agricultural MAP often contains insoluble impurities and is not suitable for hydro.
In practice
MAP is used where a grower wants phosphorus plus a little ammonium to steady pH drift in recirculating systems. It also adds nitrogen, so it does not suit a late-flower feed where N is being tapered; MKP is the better P source there. Keep total ammonium to a small share of total N, as high NH4/NO3 ratios cut cannabis yield and cannabinoids.
Units and formula
1 g/L gives about 120 mg/L (ppm) N and 266 mg/L P.
Don't confuse with
- Diammonium phosphate (DAP): (NH4)2HPO4, more ammonium and more alkaline.
- Monopotassium phosphate (MKP): P with potassium instead of ammonium.
- MAP as a shipping acronym: modified-atmosphere packaging is unrelated.
Ammonium (NH4+) is the positively charged form of nitrogen; a small share stabilises root-zone pH, but too much reduces cannabis yield and quality.pH drift is the gradual rise or fall of a nutrient solution's pH between adjustments, driven mainly by which ions the roots take up.A recirculating (closed) system returns drained nutrient solution to the reservoir to be reused, saving water and nutrients but needing more monitoring and sanitation.Monopotassium phosphate (MKP, KH2PO4) supplies about 22.7% phosphorus and 28.7% potassium with no nitrogen, and is the base of most PK boosters.Nitrate (NO3-) is the main form of nitrogen in hydroponic and soilless feeds; its uptake tends to push root-zone pH upward.A cannabinoid is any compound that binds the body's cannabinoid receptors or shares the typical cannabis terpenophenolic structure; the plant-made ones are phytocannabinoids such as THCA and CBDA.Phosphate is the ionic form in which plants absorb phosphorus, mainly H2PO4- at the normal root-zone pH of 5.5-6.5.Phosphorus (P) is a mobile macronutrient used in energy transfer (ATP), DNA and cell membranes; cannabis needs moderate amounts and gains nothing from excess.Nitrogen (N) is the macronutrient plants use most, built into proteins, chlorophyll and nucleic acids; it drives leaf and stem growth and is fully mobile.
