Copper sulfate is the bright blue salt of copper and sulfate, normally sold as the pentahydrate (CuSO4·5H2O) at about 25.5% Cu. It is soluble and also widely used as a fungicide and algicide.
In practice
In a micronutrient stock, copper is needed at very low levels, about 0.03-0.1 mg/L (ppm) in the final feedbeing reviewed. That is only a fraction of a milligram of salt per litre, so it is always dosed from a concentrated stock. Overdosing damages roots and can induce iron deficiency. Garden-store copper sulfate sold for algae control may not be pure enough for nutrition; check the grade.
Units and formula
1 mg/L of the pentahydrate gives about 0.255 mg/L (ppm) Cu.
Don't confuse with
- Bordeaux mixture: copper sulfate plus lime, a fungicide spray.
- Copper chelate (Cu-EDTA): more stable at higher pH.
- Copper ionisers: devices that release copper into water, a contamination risk in hydro.
Copper (Cu) is a micronutrient used in photosynthetic electron transport and lignin formation; plants need only traces, and excess is toxic to roots.Sulfate (SO4 2-) is the form in which plants take up sulfur, delivered mainly by magnesium sulfate and potassium sulfate in mineral feeds.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.Iron (Fe) is an immobile micronutrient needed to make chlorophyll and run electron transport; deficiency yellows new leaves between green veins.A chelate is a metal ion held by an organic molecule at several points, keeping micronutrients such as iron, zinc and manganese dissolved and available across a wider pH range.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.Nutrient toxicity is damage from an excess of an element in the plant, either directly or by blocking uptake of others; boron, manganese, copper and chloride are common culprits.
