Manganese is a micronutrient absorbed as Mn2+. It is essential to the water-splitting complex of photosystem II and activates a range of enzymes. It is largely immobile in the plant. Its availability rises sharply as root-zone pH falls.
In practice
Deficiency shows as interveinal mottling on young and middle leaves, with less contrast than iron chlorosis and sometimes small dead spots. It is most common at high pH. Toxicity is the more frequent problem in acidic soil or hydro run too low: brown speckling on older leaves and induced iron deficiency, because Mn competes with Fe. Hydro feeds usually carry roughly 0.5-1 mg/L (ppm) Mn, typically from manganese sulfate or a chelate.
Don't confuse with
- Iron deficiency: brighter yellow with sharper green veins on the newest leaves.
- Magnesium deficiency: older leaves, broad interveinal yellowing.
- Rust-coloured spots from light or pathogens: check pH and history before blaming Mn.
Myth check
When Mn toxicity appears, the fix is usually raising root-zone pH back into range, not cutting the micronutrient blend. See pH and nutrient availability.
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.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 nutrient deficiency is a shortage of an essential element in the plant tissue, causing characteristic symptoms; the cause is often pH or uptake rather than an empty feed.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.Iron (Fe) is an immobile micronutrient needed to make chlorophyll and run electron transport; deficiency yellows new leaves between green veins.Manganese sulfate (MnSO4) is the common soluble manganese source for DIY micronutrient mixes, about 32% Mn in the monohydrate form.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 (Mg) is a mobile secondary nutrient at the centre of every chlorophyll molecule; deficiency causes interveinal yellowing on older leaves.An immobile nutrient stays where it is first deposited, so its deficiency shows on young leaves and growing tips first: Ca, S, Fe, Mn, B, Cu.
