Calcium nitrate is a highly soluble salt that supplies both calcium and nitrate nitrogen. The fertiliser grade most growers buy is a double salt with a little ammonium, analysed at about 15.5% N (roughly 14.4% nitrate-N and 1.1% ammonium-N) and 19% Ca.
In practice
It is the backbone of the A part in almost every two-part mineral feed. Because it reacts with sulfate and phosphate to form insoluble precipitates, it must never be mixed with magnesium sulfate, MKP or potassium sulfate in concentrated form. In the final dilute tank, they coexist without trouble. It is hygroscopic: keep the bag sealed or it turns to slush.
Units and formula
1 g/L gives about 155 mg/L (ppm) N and 190 mg/L Ca. A feed of 0.8 g/L therefore adds roughly 150 ppm Ca and 125 ppm N.
Don't confuse with
- Calcium chloride: supplies calcium without nitrogen but adds chloride.
- Calcium carbonate (lime): insoluble, used to raise soil pH, not a hydro calcium source.
- Cal-Mag: a blended product, often based on calcium nitrate plus a magnesium salt.
Nitrate (NO3-) is the main form of nitrogen in hydroponic and soilless feeds; its uptake tends to push root-zone pH upward.Ammonium (NH4+) is the positively charged form of nitrogen; a small share stabilises root-zone pH, but too much reduces cannabis yield and quality.Sulfate (SO4 2-) is the form in which plants take up sulfur, delivered mainly by magnesium sulfate and potassium sulfate in mineral feeds.Magnesium sulfate heptahydrate, sold as Epsom salt, is the common hydro magnesium source, supplying about 9.9% magnesium and 13% sulfur.Potassium sulfate (K2SO4) supplies roughly 41-45% potassium and 17-18% sulfur with no nitrogen, useful for adding K while tapering N in late flower.Calcium chloride (CaCl2) adds calcium without nitrogen, useful for late-flower nitrogen tapering, but it adds chloride, so doses must stay modest.As a plant nutrient, chlorine is used as the chloride ion (Cl-) in tiny amounts for photosynthesis and osmotic balance; excess from water or salts is the usual problem.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.Calcium (Ca) is an immobile secondary nutrient that builds cell walls and membranes; it travels only in the transpiration stream, so deficiency appears in new growth.An A/B nutrient is a mineral feed split into two concentrates so that calcium (part A) is kept apart from sulfate and phosphate (part B), which would precipitate together.A stock solution is a concentrated nutrient mix, often 100x or 200x final strength, diluted into the reservoir; calcium and sulfate/phosphate stocks must stay separate.Per-element dosing builds a feed from individual salts or single-element stocks so each nutrient can be set independently, such as cutting nitrogen without cutting potassium.
