Zinc in Plant Health: From Leaf Expansion to Yield Optimization

Zinc (Zn) is one of the essential micronutrients for plants, absorbed primarily in the form of Zn²⁺ ions. It exhibits moderate mobility within plant tissues. In recent years, zinc deficiency has become increasingly prevalent across various crops. Since zinc is not easily translocated within plants, deficiency symptoms tend to appear first on the youngest leaves and tissues—manifesting as “white striping” in maize, “stunted seedlings” in rice, or “little leaf” disease in fruit trees. As a result, zinc fertilizers are commonly applied annually via base fertilization and foliar spraying. However, blind application often leads to waste and suboptimal results.

Physiological Functions of Zinc and the Consequences of Deficiency

1. Auxin Biosynthesis

   • Zinc promotes the synthesis of tryptophan, a precursor of the key plant hormone indole-3-acetic acid (IAA), which influences leaf size and thus photosynthetic capacity. Since 95% of crop yield comes from photosynthesis, zinc is often dubbed the “leaf enlarger.”

   • Deficiency drastically reduces auxin synthesis, especially in stems and buds, leading to small, deformed leaves, shortened internodes, and symptoms like "little leaf disease."

   
   

2. Essential for Chlorophyll Formation

   • Zinc is vital for carbonic anhydrase (CA) synthesis in chloroplasts, which catalyzes CO₂ hydration and promotes CO₂ fixation during photosynthesis.

   • Deficiency reduces CA activity, slows photosynthesis, and impairs chlorophyll synthesis, causing leaf chlorosis (e.g., white seedlings in maize).

   
   

3. Enzyme Activation

   • Zinc acts as an activator of numerous enzymes and is a structural component of RNA polymerase essential for protein synthesis.

   • Deficiency disrupts protein metabolism, leading to chlorosis, wrinkled leaves, increased empty grains, and poor pod setting in crops like soybeans.

   
   

4. Development of Reproductive Organs

   • Zinc is key to flower and fruit development.

   • In grapes, deficiency causes uneven berry sizing. In rice, it causes curled leaves, short roots, and chlorotic striping on young leaves.

   
   

5. Improved Stress Tolerance

   • Zinc enhances protein flexibility under heat stress and helps maintain photosynthesis under drought and high temperatures, thereby increasing grain weight and improving shoot-to-grain ratios.

   • Deficiency weakens stress resistance and increases disease susceptibility (e.g., tomato mosaic virus).

Causes of Zinc Deficiency in Soils and Crops

1. Organic Matter Binding

   • 50–60% of soil zinc binds with organic matter into insoluble forms.

     
     

2. Phosphate Antagonism

   • Excessive phosphate forms insoluble zinc phosphate in plant tissues, hindering zinc uptake. High nitrogen levels or certain hybrids also increase zinc demand.

     
     

3. High Soil pH

   • Soils with pH >7 are more prone to zinc deficiency.

     
     

4. Herbicide Accumulation

   • Long-term herbicide use can damage soil health and reduce zinc availability.

Zinc Deficiency Symptoms in Major Crops

• Maize: Interveinal chlorosis at leaf bases, white striping, stunted growth, barren cobs.

• Rice: Lower leaves show yellow-white streaks, upper leaves show reddish-brown spots, stunted tillering, delayed maturity, and poor seed set.

• Wheat: Grey-green young leaves, interveinal chlorosis, yellowing leaf tips and margins.

• Potato: Short internodes, small upright leaves with bronzed spots, curled edges, and poor tuber growth.

• Fruit Trees (e.g., citrus, grapes, apples): Rosetting, small clustered leaves, shortened internodes, poor fruit size and quality.

• Vegetables (e.g., tomato, cucumber, eggplant): Stunted growth, leaf yellowing, fruit deformation, and leaf curling.

Zinc Supplementation Strategies

• When to Apply: When soil zinc is below 0.5 mg/kg.

• Key Approaches:

  1. Soil improvement (e.g., straw mulching to retain moisture).

  2. Drainage improvement to avoid waterlogging in calcareous soils.

  3. Soil application: Zinc sulfate (e.g., 2 kg/acre for rice, maize).

  4. Foliar spraying: Preferred due to better absorption compared to soil-applied zinc.

Guidelines for Zinc Fertilizer Application

1. Target Sensitive Crops

   Maize, rice, peanuts, soybeans, tomatoes, beans, and fruit trees respond well.

   
   

2. Target Deficient Soils

   Apply only where deficiency is confirmed; avoid in zinc-rich soils.

   
   

3. Apply as Base Fertilizer Every Other Year

   Zinc has a long residual effect in soil. Use ~20–25 kg/ha of zinc sulfate.

   
   

4. Avoid Mixing with Pesticides During Seed Treatment

   Use 2g/kg of zinc sulfate solution; dry seeds before pesticide coating.

   
   

5. Avoid Mixing with Phosphates

   Phosphorus and zinc antagonize each other; apply zinc with acidic fertilizers or fine soil.

   
   

6. Incorporate into Soil

   Apply ~15 kg/ha zinc sulfate in furrows and cover with soil for best effect.

   
   

7. Short Dipping for Seedlings

   1% zinc sulfate solution for 30 seconds—avoid longer dips to prevent phytotoxicity.

   
   

8. Foliar Spraying for Immediate Results

   Use 0.1–0.2% zinc sulfate or chelated zinc solution; avoid spraying directly into the shoot apex.

   
   

Types of Zinc Fertilizers & Our Products

Zinc fertilizers fall into three major categories:

1. Inorganic Compounds:

   • Zinc sulfate, zinc oxide, zinc carbonate, zinc nitrate, zinc chloride.

   • Zinc sulfate (monohydrate or heptahydrate) is the most widely used globally.

     
     

2. Synthetic Chelates:

   • Chelated with agents like EDTA (e.g., EDTA-ZnNa₂), highly stable and suitable for foliar, fertigation, or hydroponic use.

     
     

3. Natural Organic Complexes:

   • Formed by reacting inorganic zinc salts with organic acids (e.g., citric acid, lignosulfonates, fulvic acids).

Our Products:

• Zinc Sulfate Monohydrate (Zn ≥ 35%): Powder or granule, highly soluble, low caking, ideal for feed use.

• Zinc Sulfate Heptahydrate (Zn ≥ 21%): White crystalline, highly water-soluble, ideal for foliar application.

• EDTA-ZnNa₂ (Zn ≥ 10%): Stable chelate that prevents precipitation with phosphates/carbonates, improving bioavailability.

🔗 Click here to learn more about chelated fertilizers:

 https://www.kelewell.de/en/post/chelated-fertilizers-a-smarter-safer-and-more-efficient-nutrition-for-modern-agriculture

Global Zinc Fertilizer Market Trends

• Market Size & Growth:

  • $3.59B (2020) → projected $6.87B (2028), CAGR: 8.4%.

  • Asia-Pacific dominates with 43% (China, India leading).

    
    

• Product Trends:

  • Zinc sulfate remains dominant (~56% market share).

  • Chelated zinc fertilizers (e.g., EDTA-Zn) growing rapidly—expected to exceed 45% by 2030.

    
    

• Regional Demand Highlights:

  • Asia: High demand in zinc-deficient rice zones (e.g., China—41% deficient soils).

  • Africa & Southeast Asia: Emerging markets, 15–20% annual growth.

  • Europe & North America: Favor chelated forms, high-tech and eco-friendly products (e.g., nano-coatings, smart blends).

    
    

• Future Outlook:

  • By 2030, global market may exceed $11B, with chelated forms accounting for >50% and Asia-Pacific contributing 60% of growth.

Conclusion

Zinc plays vital roles throughout the entire plant lifecycle, influencing yield and quality more than any other micronutrient—and in some cases even more than macronutrients. Effective supplementation requires tailored strategies based on soil testing and crop sensitivity, combining soil improvement with precision fertilization.

As the global zinc fertilizer market enters a dual-phase of technological innovation and demand expansion, chelated and slow-release products, along with precision application technologies, are becoming mainstream. Our company offers comprehensive zinc nutrition solutions adapted to diverse soil types and crop requirements, empowering high-quality, high-yield modern agriculture.