Zinc sulfate [ZnSO4]

Zinc salt (ZnSO4), a colourless or white solid, commonly sold as the heptahydrate or monohydrate.

Characteristics

Fertilizer grades contain up to about 35–36 % zinc.
Highly soluble in water, unlike zinc oxide.
Zinc is an essential micronutrient and a component of many enzymes.
Used as a zinc source in fertilizers and animal feed.

Role in the preparation: It supplies soluble zinc as a micronutrient in mineral preparations.

Caution: Causes serious eye damage, is harmful if swallowed and very toxic to aquatic life: wear goggles and gloves, keep it closed, and test the soil before adding zinc.

Sources: Zinc sulfate - Wikipedia · Zinc for crop production - University of Minnesota Extension

Documentary information: this is neither a recommendation for use nor a plant-protection or veterinary claim. Check your country's regulations before any use.