Urea is a small organic molecule, CO(NH2)2, containing 46% nitrogen. It is the world's most used nitrogen fertiliser. Plants can absorb some urea directly, but most is first converted to ammonium by urease, a nickel-dependent enzyme produced by microbes and plants.
In practice
In soil, urea behaves like a slow ammonium source and acidifies over time; it can lose nitrogen as ammonia gas if left on the surface. In hydro and soilless systems it is a poor fit: it is not counted by EC meters as an ion until converted, its conversion depends on microbial activity, and the ammonium it releases can upset the NH4/NO3 balance. Some liquid bottle nutrients and foliar products include it. On labels, urea-N is often listed separately from nitrate-N and ammoniacal-N.
Don't confuse with
- Ammonium: urea becomes ammonium; they are not the same compound.
- Urine: contains urea, but also salts and sodium; not a measured feed.
- Uric acid: a different nitrogen compound found in bird and bat manures.
Ammonium (NH4+) is the positively charged form of nitrogen; a small share stabilises root-zone pH, but too much reduces cannabis yield and quality.A soilless medium contains no mineral soil, such as peat, coco, rockwool or perlite blends, and relies mostly on the grower to supply nutrients.EC (electrical conductivity) measures how well a solution conducts electricity, a proxy for total dissolved salts; growers read it in mS/cm to gauge nutrient strength.Nitrate (NO3-) is the main form of nitrogen in hydroponic and soilless feeds; its uptake tends to push root-zone pH upward.Foliar feeding is spraying a dilute nutrient solution onto leaves for quick uptake through the leaf surface; it suits micronutrient fixes but cannot replace root feeding.Sodium (Na) is not essential for cannabis; it enters through water, softeners and some inputs, and at high levels causes salt stress and crowds out potassium and calcium.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.Nickel (Ni) is a micronutrient required for urease, the enzyme that breaks down urea; plants need only traces, which most feeds and waters already contain.
