Zinc Sulfate (ZnSO₄·H₂O and ZnSO₄·7H₂O) is the most widely used and cost-effective source of zinc for correcting one of the most common micronutrient deficiencies in world agriculture. With zinc content ranging from 22% to 35% depending on the hydrate form, our fully water-soluble zinc sulfate provides immediate plant availability, rapid deficiency correction, and exceptional return on investment. For growers facing stunted growth, poor grain fill, or “little leaf” symptoms, zinc sulfate delivers reliable results across all major crops.

I. The Critical Role of Zinc in Plant Health

Zinc is an essential micronutrient that functions as a cofactor for over 300 enzymes, directly influencing:

• Auxin (growth hormone) synthesis – Zinc is required for the production of indole-3-acetic acid (IAA), which controls cell elongation and division. Zinc deficiency causes stunted growth, rosetting, and “little leaf.”
• Protein synthesis – Zinc is a structural component of ribosomes and is essential for protein formation.
• Membrane integrity – Zinc stabilizes cell membranes, reducing leakage of sugars and amino acids.
• Pollen development and fertilization – Adequate zinc increases pollen viability, fruit set, and seed formation.
• Stress tolerance – Zinc supports antioxidant systems, improving resistance to drought, heat, and cold.

II. Recognizing Zinc Deficiency

Typical Symptoms by Crop Group

• Cereals (wheat, corn, rice): Interveinal chlorosis on young leaves, white or yellow bands near the leaf base, stunted growth, poor tillering, and “white bud” in corn. Heads may be small with shriveled grains.
• Soybeans and pulses: ”Little leaf” – very small, upright leaflets; interveinal chlorosis; delayed maturity; poor pod set.
• Fruit trees (citrus, apple, stone fruits): Irregular, small leaves clustered at shoot tips (rosette); shortened internodes; “bronzing” on older leaves; poor fruit set and quality.
• Potatoes and root crops: Stunted plants, leaf cupping, interveinal chlorosis on younger leaves, reduced tuber yield.
• Vegetables (tomato, onion, cucurbits): Stunted growth, leaf distortion, poor flowering, and fruit set.

Conditions Favoring Zinc Deficiency

• High soil pH (calcareous, alkaline soils, pH > 7.0) – zinc becomes insoluble.
• Sandy, low-organic-matter soils – low total zinc and high leaching.
• Soils with high phosphorus content – phosphorus suppresses zinc uptake.
• Cold, wet spring conditions – slow root growth limits zinc absorption.
• Over-liming – excessive lime raises pH and induces deficiency.

III. Application Methods and Recommendations

Soil Application (for long-term correction)

• Rate: 10–30 kg of ZnSO₄·H₂O (or 15–45 kg of heptahydrate) per hectare, based on soil test.
• Timing: Apply pre-plant, broadcast and incorporate into the root zone (top 10–15 cm).
• Frequency: One application typically supplies adequate zinc for 2–3 years.
• Note: On calcareous soils, banding is more effective than broadcasting.

Foliar Spray (for rapid deficiency correction)

• Concentration: 0.2–0.5% solution (200–500 g per 100 L water). Use 300–500 L of solution per hectare.
• Timing: Apply at early vegetative stages, before flowering, and again at pod or grain fill if deficiency persists.
• Frequency: 2–3 applications spaced 10–14 days apart.
• Additive: Use a non-ionic surfactant (0.1%) for better leaf coverage.
• Response: Visible greening and growth improvement within 5–7 days.

Fertigation (Drip and Sprinkler Systems)

• Rate: 2–5 kg per hectare per application (as ZnSO₄·H₂O) dissolved in irrigation water.
• Concentration: Maintain 1–5 ppm zinc in the final solution.
• Frequency: Weekly or bi-weekly during active growth.
• Advantage: Precise delivery, especially effective in sandy soils.

Seed Treatment

• Concentration: 0.2–0.5% solution; soak seeds for 8–12 hours before planting.
• Benefit: Provides early zinc for seedling establishment, improves germination, and enhances root growth.

Hydroponic Nutrient Solutions

• Target range: 0.5–2.0 ppm zinc.
• Adjustment: Use zinc sulfate as the standard zinc source; it is fully soluble and stable in nutrient solution pH 5.5–6.5.

IV. Technical Specifications

Zinc Sulfate Monohydrate (ZnSO₄·H₂O) – High Concentration Grade

• Zinc (Zn): 35% minimum
• Sulfur (S): 17% minimum
• Solubility: 960 g/L at 20°C (extremely high)
• Appearance: White free-flowing powder
• Bulk density: 1200–1400 kg/m³

Zinc Sulfate Heptahydrate (ZnSO₄·7H₂O) – Standard Agricultural Grade

• Zinc (Zn): 22.5% minimum
• Sulfur (S): 11% minimum
• Solubility: 660 g/L at 20°C
• Appearance: White to off-white crystalline powder
• Bulk density: 1000–1100 kg/m³

Quality Standards (Both Grades)

• Purity: ≥ 98%
• Heavy metals: Cd ≤ 2 ppm, Pb ≤ 10 ppm, As ≤ 2 ppm
• Chloride (Cl): ≤ 0.05%
• Insoluble matter: ≤ 0.05%
• Moisture: ≤ 0.5%

V. Crop-Specific Recommendations

Cereals (Wheat, Corn, Rice)

• Soil application: 10–20 kg/ha ZnSO₄·H₂O pre-plant increases grain yield by 15–30% in zinc-deficient soils.
• Foliar spray: 0.3–0.5% at tillering and boot stage improves grain protein and test weight.
• Response: Reduced “white bud” in corn, fewer empty heads in wheat, higher thousand-kernel weight.

Soybeans and Pulses

• Soil band or broadcast: 10–15 kg ZnSO₄·H₂O per hectare.
• Foliar: 0.3% at early flowering and pod set increases pods per plant and seed size.
• Response: 20–35% yield increase in severely deficient fields; improved protein content.

Potatoes

• Side-dress or broadcast: 10–15 kg ZnSO₄·H₂O per hectare at planting or hilling.
• Foliar supplement: 0.2% at tuber initiation reduces internal necrosis.
• Response: Higher tuber number, reduced hollow heart, better specific gravity.

Fruit Trees (Citrus, Apple, Mango)

• Soil drench: 100–200 g of ZnSO₄·H₂O per mature tree (depending on size) every 2–3 years.
• Foliar spray: 0.2% at petal fall and fruit set improves fruit size, color, and juice content.
• Response: Prevents “rosette” and leaf bronzing; increases marketable yield by 15–25%.

Vegetable Crops (Tomato, Onion, Peppers)

• Pre-plant soil incorporation: 10–15 kg ZnSO₄·H₂O per hectare.
• Foliar spray: 0.2–0.3% during early growth and fruit set.
• Response: Reduced “little leaf,” higher fruit set, improved bulb size and storage quality in onions.

VI. Economic and Environmental Advantages

Cost-Effectiveness
Zinc sulfate is the least expensive source of soluble zinc. For the same level of deficiency correction, chelated zinc products cost 3–5 times more. With a typical yield response of 15–30%, the return on investment often exceeds 5:1.

Rapid Correction
Because zinc sulfate is fully water-soluble, it becomes available to plants immediately after application. Foliar sprays can correct deficiency symptoms within one week.

Low Environmental Risk
Zinc is an essential nutrient, not a pollutant, when used at recommended rates. It binds tightly to soil organic matter and clay, so leaching is minimal. Over‑application can cause phytotoxicity but not long-term soil contamination.

VII. Compatibility and Mixing Guidelines

Compatible with

• Most nitrogen and potassium fertilizers
• Most micronutrient chelates
• Non-ionic surfactants
• Most pesticides (jar test recommended)

Incompatible with

• Highly alkaline materials (lime, wood ash, Bordeaux mixture)
• Concentrated phosphate solutions (may form zinc phosphate precipitate)
• In fertigation, do not mix with phosphates in the same stock tank; inject separately.

Mixing for Foliar Spray

1. Fill tank with water, adjust pH to 5.0–6.0 if necessary.
2. Add zinc sulfate and stir until dissolved.
3. Add other compatible products (if any) and non-ionic surfactant.
4. Use within 24 hours.

VIII. Safety and Handling

Worker Safety
Zinc sulfate is not classified as hazardous, but dust may irritate eyes and respiratory tract. Wear gloves, dust mask, and goggles when handling large quantities. In case of eye contact, rinse with water. If ingested, drink water and consult a physician.

Storage
Store in original sealed bags in a cool, dry, well-ventilated area, away from moisture and alkaline materials. Shelf life: 24 months.

Environmental Precautions
Avoid spills into waterways. If spilled, sweep up and dispose of according to local regulations.

IX. Quality Assurance and Certifications

Our zinc sulfate is produced in ISO 9001:2015 and ISO 14001:2015 certified facilities. Each batch is tested for Zn content, heavy metals, solubility, and particle size distribution. Certificates of Analysis accompany every shipment. OMRI‑listed grades (for organic farming) are available.

X. Why Choose Our Zinc Sulfate

• High purity – Low cadmium and lead, meeting international fertilizer standards.
• Consistent particle size – Uniform crystals for easy blending and accurate application.
• Rapid solubility – Dissolves completely in cold water; ideal for foliar and fertigation.
• Technical support – Our agronomists help you interpret soil tests, design zinc programs, and correct deficiency quickly.
• Flexible packaging – 25 kg bags, 1‑ton FIBCs, and bulk containers.