Manganese sulfate is the salt of manganese and sulfate, usually sold as the monohydrate (MnSO4·H2O) at about 32% Mn. A tetrahydrate form also exists, with less Mn per gram (about 24.6%). It is soluble and pale pink.
In practice
It is the usual Mn source in home-made micronutrient stocks, often alongside zinc sulfate, copper sulfate, boric acid and sodium molybdate, with chelated iron added separately. The final solution typically needs only about 0.5-1 mg/L (ppm) Mn, so the salt is dosed in milligrams per litre, ideally from a concentrated stock rather than weighed fresh each time. In high-pH conditions, chelated manganese is more reliable than the sulfate.
1 mg of the monohydrate per litre gives about 0.32 mg/L (ppm) Mn. To reach 0.5 ppm Mn, add about 1.6 mg/L.
Don't confuse with
- Magnesium sulfate: Epsom salt; Mg, not Mn.
- Manganese chelate (Mn-EDTA): stays available at higher pH.
Manganese (Mn) is a micronutrient that splits water in photosynthesis and activates many enzymes; low pH can raise it to toxic levels.Sulfate (SO4 2-) is the form in which plants take up sulfur, delivered mainly by magnesium sulfate and potassium sulfate in mineral feeds.Copper sulfate pentahydrate (CuSO4·5H2O), about 25.5% copper, supplies trace copper in micronutrient mixes and is toxic to roots in excess.Sodium molybdate dihydrate (Na2MoO4·2H2O), about 39.7% molybdenum, is the common Mo source for micronutrient mixes, used in microgram-per-litre amounts.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.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.Magnesium sulfate heptahydrate, sold as Epsom salt, is the common hydro magnesium source, supplying about 9.9% magnesium and 13% sulfur.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.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.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.
