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Zinc Sulfate vs. Chelated Zinc EDTA for Apple Orchards

Orchardist asks if zinc sulfate and chelated zinc EDTA (12%) are interchangeable. Seller claims they're the same.

Key Differences

Property	Zinc Sulfate	Chelated Zinc EDTA
Chemical form	ZnSO₄·7H₂O (inorganic salt)	Zn-EDTA complex (organic chelate)
Solubility	High in water	High in water
Soil behavior	Quickly binds to soil particles, becomes unavailable	Remains soluble, mobile in soil
Foliar absorption	Moderate	Superior—chelate facilitates leaf penetration
pH stability	Precipitates at high pH	Stable across wider pH range
Cost	Lower	Higher

Recommendation for Apple Orchards

Use chelated zinc EDTA for:

Foliar sprays: Better absorption, less phytotoxicity risk
High pH soils: Remains available where zinc sulfate locks up
Dormant/delayed dormant: More reliable uptake

Zinc sulfate is adequate for soil application in acidic soils but less efficient. Seller's claim is incorrect—they are chemically and functionally different. For apples, chelated zinc is the professional standard.

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