Iron is one of the most critical micronutrients for plant health, and ferrous sulfate (FeSO₄·7H₂O) provides iron in a highly soluble, immediately available form. With 19% iron and 11% sulfur, this blue-green crystalline product rapidly corrects iron deficiency (interveinal chlorosis) in a wide range of crops, from fruit trees and vines to ornamentals and field crops. For growers facing yellowing leaves, poor growth, and reduced yields due to iron shortage, ferrous sulfate is the most cost‑effective and reliable solution.

I. The Critical Role of Iron in Plants

Chlorophyll Synthesis
Iron is essential for the formation of chlorophyll – the green pigment that captures sunlight for photosynthesis. Without adequate iron, leaves turn pale yellow or white between the veins (interveinal chlorosis), while veins often remain green. In severe cases, entire leaves become yellow or white, and growth stops.

Enzyme Activation and Metabolism
Iron acts as a cofactor for many enzymes involved in respiration, nitrogen fixation, and electron transport. It is also required for the synthesis of certain proteins and for the reduction of nitrate to ammonium.

Stress Tolerance
Iron‑sufficient plants produce stronger cell walls and more robust antioxidant systems, improving resistance to drought, temperature extremes, and fungal diseases.

II. Recognizing Iron Deficiency

Typical Symptoms

• Interveinal chlorosis on young leaves (iron is immobile, so symptoms appear first on new growth).
• In severe cases, new leaves may be entirely white, with scorched margins.
• Reduced shoot growth, smaller leaves, and poor fruit set.
• On acid‑loving plants (azaleas, rhododendrons, blueberries, citrus) and on calcareous (high pH) soils.

Common Causes

• High soil pH (alkaline, calcareous soils) – iron becomes insoluble.
• Excess phosphorus or bicarbonate in irrigation water.
• Poorly drained, waterlogged soils.
• Cold soil temperatures that reduce root activity.

Crops Most Sensitive to Iron Deficiency

• Fruit trees: citrus, apple, pear, peach, grape.
• Vegetables: tomato, pepper, potato, beans, spinach.
• Ornamentals: roses, azaleas, gardenias, hydrangeas.
• Field crops: soybean, peanut, sorghum, cotton.

III. Application Methods

Soil Application (for long‑term correction)

• Rate: 50–200 kg per hectare, depending on soil test and severity.
• Broadcast and incorporate into the root zone (top 10–15 cm) before planting.
• For trees: 100–500 g per tree, depending on size, spread around the drip line and water in.
• Caution: Ferrous sulfate rapidly oxidizes in soil to insoluble ferric forms; for alkaline soils, combine with organic matter (compost) or acidifying materials (sulfur) for better persistence.

Foliar Spray (for rapid green‑up)

• Concentration: 0.2–0.5% solution (200–500 g per 100 L water). Use 500–1000 L of spray solution per hectare.
• Timing: Apply at the first sign of chlorosis, repeat every 10–14 days until symptoms disappear.
• Critical: Use a non‑ionic surfactant (0.1%) and spray in the early morning or late evening to avoid leaf burn. Do not mix with alkaline pesticides.
• Response: New leaves greening within 5–7 days.

Fertigation and Drip Systems

• Rate: 5–15 kg per hectare per application, dissolved in water.
• Check compatibility: ferrous sulfate can precipitate with phosphates and bicarbonates. If water has high pH or bicarbonate, use a chelated iron product for fertigation.
• For open field, apply as a single drench at planting.

Chelated Iron vs. Ferrous Sulfate

• Ferrous sulfate is inexpensive and works well in foliar sprays and in acidic soils or soilless media.
• Chelated iron (EDTA, DTPA, EDDHA) is more expensive but remains stable in high‑pH solutions and soil. For calcareous soils (pH >7.5) or high‑bicarbonate irrigation water, chelates are strongly recommended.
• Use ferrous sulfate as a cost‑effective starter or for foliar correction.

IV. Technical Specifications (Ferrous Sulfate Heptahydrate, Agricultural Grade)

Chemical Properties

• Formula: FeSO₄·7H₂O
• Iron (Fe): 19.0% minimum (as ferrous iron)
• Sulfur (S): 11.0% minimum (as SO₄)
• Molecular weight: 278.02 g/mol
• Solubility: 480 g/L at 20°C (fully soluble)
• pH of 1% solution: 3.5–4.5 (acidic)

Physical Properties

• Appearance: Blue‑green crystalline powder or granules
• Bulk density: 900–1100 kg/m³
• Particle size: 0.5–2.0 mm (standard), fine powder available
• Moisture: ≤ 0.5%
• Hygroscopicity: moderate; store in sealed bags.

Quality Standards

• Purity: ≥ 98%
• Heavy metals: Pb ≤ 10 ppm, As ≤ 2 ppm, Cd ≤ 1 ppm
• Insoluble matter: ≤ 0.05%

V. Crop‑Specific Benefits

Citrus
Iron chlorosis (yellowing of young leaves with green veins) is widespread in calcareous soils. Soil application of ferrous sulfate (200–500 g per tree mixed with organic matter) in late winter, followed by foliar sprays (0.3% solution) in spring, restores green foliage, improves fruit size, and reduces drop. Yield increases of 20–30% are common.

Grapes
Apply 0.3–0.5% foliar spray at early shoot growth and again at fruit set. Iron‑sufficient vines produce larger clusters, higher sugar content (Brix), and fewer shot berries. In alkaline vineyards, annual soil applications of 150–300 kg/ha ferrous sulfate plus sulfur help maintain vine health.

Tomatoes and Peppers
Iron deficiency causes yellow upper leaves and poor fruit set. One or two foliar sprays (0.2%) at transplanting and before flowering quickly corrects symptoms. For soilless (hydroponic) tomatoes, ferrous sulfate is the standard iron source; use at 2–4 ppm Fe in the nutrient solution.

Lawns and Turf
Iron sulfate is widely used for “iron‑greening” of turf without promoting excessive growth. Apply 2–5 kg per 1000 m² dissolved in water or as a granular product. Turf turns deep green within days, and iron also suppresses moss and some broadleaf weeds.

Blueberries and Acid‑Loving Ornamentals
Blueberries require acid soil (pH 4.5–5.5). Ferrous sulfate both acidifies the soil and supplies iron. Apply 50–100 g per bush in early spring, mixed into the mulch. For azaleas and rhododendrons, a 0.2% foliar spray after bloom prevents chlorosis.

Soybeans and Peanuts
Iron deficiency (iron chlorosis) in high‑pH soils can severely reduce yields. In‑furrow application of ferrous sulfate (50–100 kg/ha) at planting or foliar sprays at V3‑V5 growth stage can increase pod set and grain protein.

VI. Correcting Chlorosis – A Practical Protocol

1. Diagnose: Confirm iron deficiency by testing young leaves (<30 ppm Fe) or soil pH (>7.0) with high bicarbonate.
2. Foliar First: For standing crops with visible chlorosis, apply a 0.3% ferrous sulfate solution with a wetting agent. Repeat in 7–10 days if needed.
3. Soil Treatment for Prevention: In known iron‑deficient fields, incorporate ferrous sulfate (100–200 kg/ha) plus sulfur (100–200 kg/ha) 2–4 weeks before planting. This lowers soil pH and increases iron availability.
4. For Orchards: In spring, apply 200–500 g ferrous sulfate per tree (mixed with compost or sulfur) into the drip line irrigation. Follow with 2–3 foliar sprays during active growth.
5. Monitor: Once greened, maintain with regular soil acidification and occasional foliar applications.

VII. Environmental and Safety Profile

Soil Effects
Ferrous sulfate is not persistent; ferric iron forms insoluble oxides that do not leach. Over‑application can cause root scorch, especially in sandy soils. Always follow recommended rates.

Water Quality
Do not apply ferrous sulfate to water bodies or near aquatic environments; high iron levels can be toxic to fish.

Safety Precautions
Ferrous sulfate may irritate skin and eyes. Wear gloves, goggles, and dust mask when handling. In case of eye contact, flush with water. If swallowed, drink water and seek medical advice. Store in a cool, dry, well‑ventilated area away from moisture and alkaline materials.

Storage
Keep in original sealed bags. Shelf life: 24 months. Protect from heat and direct sunlight.

VIII. Quality Assurance and Certifications

Our ferrous sulfate heptahydrate is produced in ISO 9001:2015 certified facilities. Each batch is tested for iron content, solubility, heavy metals, and moisture. Certificates of Analysis are provided with every shipment.

IX. Why Choose Our Ferrous Sulfate

High Solubility
Our fine crystals dissolve rapidly in water, leaving no sediment, making them ideal for foliar sprays and liquid drenches.

Consistent Quality
We maintain tight control over particle size and iron content, ensuring reliable field results.

Cost‑Effective
Ferrous sulfate is the most affordable source of soluble iron. For foliar correction of chlorosis, it is often 5–10 times cheaper than chelates.

Technical Support
Our agronomists help you diagnose iron deficiency, select the right application method (foliar vs. soil), and develop a long‑term iron management program.