Ferrous Sulphate
The iron fertiliser for pale, yellow-between-the-veins new leaves. On high-pH soils, spraying it on the leaf beats feeding it to the soil.
- Composition
- Fe ~19% (heptahydrate)
- Form
- Pale green crystals
- Price
- Low
- Best for
- Iron deficiency (chlorosis of new leaves)
Overview
Ferrous sulphate (about 19% iron as the heptahydrate) corrects iron deficiency, which shows as interveinal chlorosis — the youngest leaves turn pale yellow while the veins stay green, the reverse of nitrogen’s bottom-up pattern. It is common on calcareous and high-pH soils, in aerobic (upland) rice, and in fruit crops like citrus and grapes.
The catch is that iron applied to a high-pH soil is quickly converted to a form the plant cannot take up — "fixed" — so soil application is often inefficient and short-lived. That is why the reliable route on these soils is a foliar spray, putting the iron directly onto the leaf where the crop can use it, repeated as the deficiency returns.
What it is and when to reach for it
- A micronutrient fertiliser for iron deficiency — reach for it when the newest leaves yellow between green veins.
- It is most needed on calcareous, high-pH soils, in upland rice, and in citrus and grapes.
- Confirm it is iron (new leaves, not old) — the pattern is the reverse of nitrogen deficiency.
How to apply it well
- Foliar is the reliable route: spray 0.5–1% ferrous sulphate (0.5–1 kg in 100 L water) on the affected leaves, repeated every 10–15 days until green returns.
- A pinch of citric acid or lime in the spray can improve uptake and reduce leaf spotting.
- On soils where it is worth trying, apply ferrous sulphate mixed with plenty of FYM/compost, which helps keep the iron available.
Common mistakes
- Relying on soil-applied iron on a high-pH soil, where it is fixed before the crop can use it.
- Confusing iron deficiency (new leaves) with nitrogen deficiency (old leaves) and treating the wrong one.
- Spraying a too-strong solution in hot sun, which scorches the leaves.
Organic alternative
FYM / compost + correcting pH
Heavy organic matter keeps iron more available, and where practical, lowering a high soil pH is the durable fix; a standing deficiency still needs a foliar ferrous sulphate spray.
Crops it is used on
Open a crop for its full nutrient schedule.
Common questions
How do I know it is iron deficiency and not nitrogen?
Look at which leaves and the pattern. Iron deficiency yellows the youngest, topmost leaves and leaves the veins green (interveinal chlorosis). Nitrogen deficiency yellows the oldest, lowest leaves first and is an even yellowing. If it is the new leaves with green veins, it is iron.
Why does soil-applied iron not work well?
On calcareous, high-pH soils, iron applied to the soil is rapidly converted to a form the plant cannot absorb — it gets "fixed". That is why a foliar spray, which puts iron straight onto the leaf, is the reliable way to correct iron deficiency on those soils.
How do I make an iron foliar spray?
Dissolve about 0.5–1 kg of ferrous sulphate in 100 litres of water (0.5–1%) and spray the affected leaves in the cool morning or evening. Repeat every 10–15 days until the new growth greens up. A little citric acid can improve uptake.
Composition and doses follow ICAR / Soil Health Card guidance; prices are the notified subsidised rates for the season shown and are guidance, not a quote. A soil test for your field always beats a general rate. See our editorial policy.