Zinc Sulfate Heptahydrate (fertilizer grade) is a chemical compound with the formula ZnSO4·7H2O. It is commonly used as a source of zinc in the agricultural industry, particularly as a micronutrient fertilizer. Zinc is an essential element required for a wide range of biological functions in plants, including enzyme activation, protein synthesis, and growth regulation.
Here are some key aspects of Zinc Sulfate Heptahydrate:
Characteristics of Zinc Sulfate Heptahydrate (Fertilizer Grade):
Zinc Content: Typically, the fertilizer grade of zinc sulfate heptahydrate contains about 21-22% zinc and 11-12% sulfur.
Solubility: This compound is highly soluble in water, which makes it easily absorbable by plants when applied to the soil or as a foliar spray.
Form: It usually comes in the form of white crystals or granules that dissolve in water to form a clear solution.
Application: It can be applied in solid granular form directly to the soil or dissolved in water and applied as a liquid.
Molecular Weight: 287.6 g/mol
CAS Number: 7446-20-0
Areas of Application：
Agriculture (As Fertilizer):
The primary use of zinc sulfate heptahydrate in agriculture is to correct zinc deficiency in crops, which is common in many types of soils, especially alkaline and sandy soils. Zinc deficiency in plants can lead to stunted growth, delayed maturity, and poor crop yields.
Recognizing Zinc Deficiency:
Before applying zinc sulfate heptahydrate, it's important to recognize the signs of zinc deficiency in plants, which can include:
1.Reduced growth and stunted plants
2.Smaller leaves, often with a yellowish color between veins (chlorosis)
3.Distorted leaf shapes or a shortening between leaf nodes
4.Reduced flowering and fruiting
Zinc is a critical micronutrient for many crops, but certain ones are more susceptible to zinc deficiency and may require zinc sulfate heptahydrate applications more than others. Here's a list of specific crops that often benefit from zinc supplementation:
1. Corn (Maize):
Corn is particularly sensitive to zinc deficiency, especially in cool, wet soils with high pH levels. Zinc is vital for optimal growth and development, affecting leaf size, stalk strength, and ear development.
2. Rice:
Rice can exhibit poor growth and reduced yield under zinc-deficient conditions, often manifested as bronzing of the leaves. Zinc is crucial for rice, especially when grown in alkaline or saline soils.
3. Wheat:
Zinc deficiency in wheat can lead to shorter plants with fewer tillers and smaller leaves. It's often necessary to apply zinc in regions with high pH soils or sandy soils low in organic matter.
4. Fruit Trees:
Certain fruit trees, such as apple, peach, and citrus, may show signs of zinc deficiency, including small leaves, rosetting, and poor fruit set. Zinc sulfate heptahydrate can be applied as a soil amendment or as a foliar spray to address these issues.
5. Vegetables:
A variety of vegetables, including beans, potatoes, and leafy greens like spinach and lettuce, can benefit from zinc applications if the soil is deficient. Symptoms of deficiency include reduced growth and chlorosis between the veins of the leaves.
Soil Application:
Pre-Planting Application: Zinc sulfate heptahydrate can be applied to soil before planting. It can be broadcast and tilled into the soil or applied in bands near the seed rows. The application rate typically varies from 5 to 10 pounds per acre (5.6 to 11.2 kg/ha), but this can vary based on soil type, crop being grown, and the extent of zinc deficiency as determined by a soil test.
Side-Dressing: For crops already established, zinc sulfate can be side-dressed around the base of the plants or along the rows. This method helps provide zinc directly where plants can absorb it through their roots.
Foliar Application:
Spray Solution: Zinc sulfate heptahydrate can be dissolved in water and sprayed directly onto the leaves of plants. This method allows for quick absorption by the plant and is particularly useful when soil conditions limit the uptake of zinc.
Application Rates: The concentration of the spray solution usually ranges from 0.5% to 2%, depending on the crop sensitivity and the severity of the deficiency. Foliar application is typically done during critical growth stages such as flowering or fruit set.
Soil Remediation:
In areas where soil is contaminated with heavy metals, zinc sulfate heptahydrate can be used to immobilize the contaminants, reducing their bioavailability and mitigating environmental risks.
Hydroponics and Aquaponics:
In hydroponic systems, zinc sulfate heptahydrate is added to the nutrient solution to ensure adequate zinc levels. The concentration needs to be carefully controlled to avoid toxicity.
Factors Influencing Application:
Soil pH: Zinc availability decreases in high pH soils. In such cases, higher rates of zinc sulfate may be required.
Soil Type: Sandy soils or soils high in phosphorus and iron may require more zinc.
Crop Requirement: Some crops are more susceptible to zinc deficiency and may require higher application rates.
Safety and Environmental Considerations:
When applying zinc sulfate heptahydrate, it’s important to follow label instructions and safety precautions to avoid over-application, which can lead to toxicity in plants and affect water quality.
Protective gear should be worn during application to prevent skin contact and inhalation.
It’s essential to avoid runoff into waterways, as excessive zinc can be harmful to aquatic life.
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