Ammonium nitrate is a salt containing nitrogen in both its main plant-available forms: about 17% as ammonium and 17% as nitrate, for 34-35% total N. It is very soluble and strongly hygroscopic.
In practice
In mineral hydro it is used sparingly to add an ammonium fraction, which offsets the pH rise caused by nitrate uptake. Langenfeld and Bugbee examined nitric acid and ammonium nitrate as tools for pH control in recirculating systems. Too much shifts the NH4/NO3 balance and harms cannabis yield and quality. Pure ammonium nitrate is restricted or regulated in many places because it is an oxidiser with explosive potential; many growers use calcium ammonium nitrate or the ammonium in fertiliser-grade calcium nitrate instead. Check local rules.
1 g/L gives about 340-350 mg/L (ppm) N, half as NH4-N and half as NO3-N.
Don't confuse with
- Calcium ammonium nitrate (CAN): ammonium nitrate blended with limestone or dolomite.
- Ammonium sulfate: ammonium with sulfate, more acidifying.
- Urea: an organic N compound needing enzymatic conversion.
Ammonium (NH4+) is the positively charged form of nitrogen; a small share stabilises root-zone pH, but too much reduces cannabis yield and quality.Nitrate (NO3-) is the main form of nitrogen in hydroponic and soilless feeds; its uptake tends to push root-zone pH upward.pH measures how acidic or alkaline a solution is on a 0–14 scale; in growing it controls nutrient uptake, with soil best near 6.0–7.0 and hydro 5.5–6.5.Nitric acid (HNO3) lowers pH while adding nitrate nitrogen; growers use it to neutralise hard-water alkalinity, often alongside or instead of phosphoric acid.A recirculating (closed) system returns drained nutrient solution to the reservoir to be reused, saving water and nutrients but needing more monitoring and sanitation.Calcium nitrate is the standard hydroponic calcium source, supplying about 19% calcium and 15.5% nitrogen, mostly as nitrate.Sulfate (SO4 2-) is the form in which plants take up sulfur, delivered mainly by magnesium sulfate and potassium sulfate in mineral feeds.Urea is a 46% nitrogen organic compound that soil enzymes convert to ammonium; it is cheap in field fertilisers but a poor choice for hydroponic cannabis.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.
