A stock solution is a concentrated solution of one or more fertiliser salts, made at a fixed multiple of feeding strength, typically 100x or 200x. It is diluted into the reservoir or injected through a dosing system to give the final nutrient solution.
In practice
Stocks make home-made feeds practical: weighing salts once for 10 litres of 100x stock covers 1,000 litres of feed, and micronutrients that would need milligram weighing become millilitre doses. The rule is separation. Calcium salts go in tank A; sulfates and phosphates go in tank B; iron chelate usually goes in A. Solubility limits how strong a stock can be; potassium sulfate is the common bottleneck. Store stocks cool and dark, label them with recipe and date, and use acid-resistant containers if acid is included.
For a stock at multiple M: grams of salt per litre of stock = target mg/L of element ÷ (element % × 10) × M.
Don't confuse with
- Stock plant: a mother plant kept for cuttings.
- Working solution: the diluted feed that reaches the roots.
A micronutrient is an essential element plants need only in trace amounts, below a few mg/L: iron, manganese, zinc, copper, boron, molybdenum, chlorine and nickel.Sulfate (SO4 2-) is the form in which plants take up sulfur, delivered mainly by magnesium sulfate and potassium sulfate in mineral feeds.Phosphate is the ionic form in which plants absorb phosphorus, mainly H2PO4- at the normal root-zone pH of 5.5-6.5.An iron chelate is iron bound to an organic molecule (EDTA, DTPA or EDDHA) that keeps it dissolved and available; each type holds up to a different pH.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.A genetic bottleneck is a sharp drop in the number of breeding plants, after which the population carries only a fraction of its former genetic diversity.A mother plant is a female kept permanently in vegetative growth to supply cuttings, so a selected genotype can be propagated as clones indefinitely.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.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.Ppm of an element means milligrams of that element per litre of solution (mg/L), the unit nutrient recipes use; it is not the ppm shown on an EC meter.Calcium nitrate is the standard hydroponic calcium source, supplying about 19% calcium and 15.5% nitrogen, mostly as nitrate.
