Ferrous Sulphate (Iron Sulphate) is a single-ingredient mineral amendment that supplies iron and sulphur. It comes as a dried, free-flowing grade that can be applied to soil or as a foliar spray. Its main job is correcting iron chlorosis.
What It Does
Corrects iron chlorosis. Iron is essential for chlorophyll production. Ferrous sulphate delivers iron in the Fe²⁺ form that plants take up directly, restoring green colour and normal photosynthesis.
Supplies sulphur. Alongside iron, it contributes sulphur, a nutrient tied to protein formation and overall plant vigour that is easy to overlook on lighter or heavily cropped soils.
Gently lowers root-zone pH. As iron oxidizes and reacts in the soil, it releases hydrogen ions that acidify the immediate root zone. The effect is localized and modest rather than a whole-soil correction, so treat it as a small pH nudge alongside its main job of supplying iron, not as a way to acidify a bed on its own.
How to Use
Most growers never need this. In a soil built up with aged manure or compost and balanced organic amendments, iron is usually available, and true iron deficiency is rare. It shows up mainly on high-pH or heavily limed mineral soils.
Start with a test. Yellowing is more often a pH problem than an iron shortage, and adding iron will not fix a pH problem. Apply ferrous sulphate only when a soil or tissue test confirms an iron deficiency, and follow the rate your test results or an agronomist recommend for your soil and crop.
Guaranteed Analysis and Specifications
Iron (Fe): 20%, water-soluble
Sulphur (S): 12%
Form: ferrous sulphate heptahydrate (FeSO₄·7H₂O), blue-green crystalline; CAS 7782-63-0
Particle size: 95% between 150 µm and 1.18 mm (-16 to +100 mesh)
Solubility: readily water-soluble; jar test before injecting into irrigation lines
Storage and Safety
Store sealed in a cool, dry place, ideally below 24°C (75°F). The material draws moisture and will compact or cake in heat or humidity.
Wear gloves and eye protection when handling, and avoid breathing the dust. Ferrous sulphate is harmful if swallowed and can cause skin and serious eye irritation, so wash hands after handling and keep it away from children and pets.
Precautions: Stains concrete, stone, siding, decking, equipment, and clothing permanently. Cover or wet down hard surfaces before applying and rinse overspray immediately. Keep children and pets off treated turf until dry or watered in. Keep out of reach of children; ingestion of iron salts is a serious poisoning hazard. Harmful to aquatic life. Do not apply near water or when heavy rain is forecast. Wear gloves and eye protection.
Approved for Use in Organic Production
Ferrous Sulphate is permitted for use in organic production under CAN/CGSB-32.310-2026 and CAN/CGSB-32.311-2026 for correcting a documented iron deficiency. Keep a soil or tissue test on file to support its use in a certified organic operation.
