Controlling Zinc Deficiency in Wheat Crop

Recognising Zinc Deficiency

• Symptoms usually appear on younger leaves first.
• Leaves show yellowing (chlorosis) between the veins, especially near the base.
• Stunted growth and reduced plant height.
• In severe cases, leaves may develop brownish or purplish spots, and plants might die.
• Overall, the crop looks unhealthy and lacks vigour.

Preventive Measures

Soil Application: This is the most effective long-term solution. Apply zinc sulfate heptahydrate (ZnSO4.7H2O) before sowing or at the time of sowing.

Mix the zinc sulfate thoroughly with the soil or broadcast it evenly. It is best applied with other basal fertilizers.

Seed Treatment: Treating wheat seeds with zinc can provide initial zinc nutrition to young seedlings.

• Mix 5-10 grams of zinc sulfate heptahydrate per kg of seed.
• Alternatively, use commercial zinc-coated seeds or formulations designed for seed treatment.

Curative Measures: Foliar Spray

When deficiency symptoms appear in standing crops, foliar application is the quickest way to correct it.

• Preparation: Dissolve 0.5% zinc sulfate solution. This means 5 grams of zinc sulfate heptahydrate per litre of water. Add 2.5 grams of unslaked lime (calcium oxide) per litre to neutralise acidity and prevent leaf burn.
• Application:
  • Spray 2-3 times at 10-15 day intervals, starting when symptoms are first observed (usually 30-45 days after sowing).
  • Ensure complete coverage of the foliage.
  • Spray early in the morning or late in the afternoon to avoid scorching and improve absorption.

Factors Influencing Zinc Availability

• Soil pH: Zinc availability decreases significantly in alkaline soils (pH > 7.0). Many Indian soils are alkaline.
• Organic Matter: Soils low in organic matter often have less available zinc. Adding farmyard manure (FYM) or compost can improve zinc availability.
• Phosphorus Levels: High phosphorus application can sometimes induce zinc deficiency, as phosphorus and zinc can interact negatively. Maintain a balanced NPK application.
• Soil Texture: Sandy soils tend to leach zinc more easily, while heavy clay soils can fix zinc, making it less available.
• Crop Type: Wheat is moderately sensitive to zinc deficiency compared to some other crops.

Best Practices for Zinc Management

• Soil Testing: Regularly test your soil to determine its zinc status before sowing. This helps in deciding the correct dose.
• Integrated Nutrient Management: Combine organic manures (FYM, compost) with chemical fertilizers. Organic matter improves soil structure and nutrient availability.
• Balanced Fertilization: Avoid excessive application of phosphorus, which can worsen zinc deficiency.
• Timely Application: Apply zinc at critical growth stages for wheat, especially during tillering and early growth.

Effective control of zinc deficiency in wheat involves a combination of preventive measures like soil application of zinc sulfate before sowing and curative foliar sprays if symptoms appear. Understanding your soil type and pH, along with regular soil testing, is key to successful zinc management for healthy wheat yields.