Iron Nutrition for Crops: Application Strategies, Benefits, and Global Trends

Iron, as an essential micronutrient for plant growth, participates in chlorophyll synthesis, respiration, and redox reactions—processes that are vital for maintaining normal crop development. Although iron is abundant in soils, the proportion available for direct plant uptake is very low, typically less than 10%. Regions such as the Mediterranean, the arid belt of Central Asia, the western Great Plains of North America, and the calcareous soils of northern China are particularly prone to iron deficiency stress. Therefore, the scientific use of iron fertilizers has become a core strategy to correct iron deficiency in global intensive agriculture and specialty crop cultivation, with application modes varying significantly across countries according to their agricultural characteristics.

I. Agricultural Application Scenarios and Core Value

The use of iron in agriculture spans the entire crop growth cycle, with applications and value dynamically adjusted based on crop type, soil conditions, and growth stage. Its roles are mainly reflected in three dimensions:

1. Soil Improvement and Basic Nutrient Supply

   On calcareous soils with high pH or in fields suffering iron fixation due to continuous cropping, applying iron fertilizers as base dressing can gradually improve the rhizosphere environment and increase soil-available iron. In intercropping of cereals with legumes, iron application significantly increases active iron content in young leaves of legumes. When combined with NPK fertilizers, it further enhances iron accumulation in grains. In orchards, mixing iron fertilizers with organic manure for pit application effectively alleviates root vitality decline caused by soil iron deficiency.

   
   

2. Foliar Nutrition Supplementation and Stress Correction

   When crops show typical iron deficiency symptoms, foliar spraying is the preferred rapid intervention. Early deficiency appears as interveinal chlorosis of new leaves; in severe cases, leaves develop brown spots and gradually necrotize. Foliar application bypasses soil absorption barriers, allowing direct uptake by leaves. Spraying before bud break or during chlorosis in fruit trees, combined with urea or other nitrogen fertilizers, greatly enhances greening effects and avoids the issue of spotted recovery or persistent chlorosis when iron is applied alone.

   
   

3. Quality Enhancement and Physiological Function Reinforcement

   Iron is involved in chloroplast structure formation. Adequate supply improves photosynthetic efficiency and nutrient accumulation. In specialty crops, proper iron application enhances fruit color, flavor, and vitamin C content. In cereals, iron fertilization improves stress resistance and reduces yield losses from drought, pests, and diseases.

II. Core Advantages and Major Limitations

Core Advantages

1. Precise and efficient physiological regulation: Iron fertilizers directly participate in enzymatic reactions, quickly activating chlorophyll synthesis. Foliar sprays typically relieve chlorosis within 7–10 days, with especially strong effects in fruit trees and vegetables.

2. Compatibility with multiple fertilization systems: Can be applied as basal, seed, or topdressing fertilizer, adaptable to traditional broadcasting and modern fertigation (drip/sprinkler).

3. Synergistic improvement of fertilizer efficiency: Organic iron fertilizers enhance soil microbial activity and structure, indirectly improving nitrogen and phosphorus uptake, forming a “nutrient synergy effect.”

4. Ensures food safety and quality: Proper iron fertilization raises iron content in edible parts, improving nutritional value. Compliant iron fertilizers leave no harmful residues, aligning with green agriculture standards.

   Major Limitations

5. Poor adaptability to alkaline soils: Soluble inorganic iron fertilizers easily form insoluble hydroxides in calcareous soils, drastically reducing efficiency even with higher application rates.

6. Product stability varies: EDTA-chelated iron is unstable and may degrade into persistent pollutants; inorganic iron fertilizers absorb moisture and cake, affecting uniform application.

7. High technical requirements: Incompatible with certain fertilizers/pesticides (risk of leaf burn or fixation).

8. Cost–benefit challenges: Highly effective chelated irons are costly, while low-cost inorganics require frequent applications, increasing labor and secondary salinization risks.

III. Main Product Types and Technical Features

Product Type	Core Components	Key Advantages	Suitable Scenarios	Main Application Regions	Compliance Features
Inorganic Iron	Ferrous sulfate heptahydrate, blue iron ore	Low cost, widely available; base or foliar use	Acidic soils, quick foliar correction	Asia, Africa (smallholders)	No global restrictions; moisture-sensitive
Chelated Iron	EDDHA, EDDS, IDHA	Stable, high mobility/utilization	Alkaline soils, cash crops	Europe, North America, Israel	EDDS/IDHA are biodegradable, EU-compliant
Organic Iron	Humic acid iron, lignosulfonate iron	Long-lasting, soil improvement, safe	Continuous cropping, orchards, vegetables	South America, Australia, China	Suitable for organic farming, EU certified
Functional Iron	Sugar alcohol iron, amino acid iron	Stable at low temp (−30 °C), bidirectional transport	Winter greenhouse crops, foliar feeding	North America, Europe (protected crops)	High foliar absorption, for high-value crops

Key Highlights:

Inorganic iron fertilizers: Represented by ferrous sulfate, applied at 3–5 kg/acre to soil or 0.2–1% foliar spray. Low cost, but soil effect is highly influenced by pH; better suited to acidic soils or mixed with organic manure.

Link: Ferrous sulfate tetrahydrate information

Link: Ferrous sulfate heptahydrate information

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Chelated iron fertilizers: EDDHA contains higher iron content; foliar spray at 1000× dilution achieves ideal results. In alkaline soils, utilization is 3–5× that of inorganic iron. Biodegradable EDDS and IDHA avoid environmental residue risks.

Link: EDDHA Fe 6% information

Organic iron fertilizers: Humic acid iron improves soil micro-ecology and prolongs iron release. Used with drip irrigation, it achieves “nutrient slow release + soil improvement,” especially suitable for perennial crops like fruit trees.

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Functional iron fertilizers: Sugar alcohol iron contains natural polyol carriers that can move freely in xylem and phloem, delivering iron precisely to new leaves and young fruits, solving the “transport barrier” of traditional iron fertilizers.

IV. Scientific Application and Key Techniques

Dosage Guidelines

• Soil application: Field crops: 3–5 kg ferrous sulfate/acre or 0.5–1 kg chelated iron/acre. Orchards: 0.2–0.5 kg ferrous sulfate/tree mixed with organic manure.

• Foliar sprays: 0.3–0.5% ferrous sulfate or 1000× dilution of chelated iron; repeat every 7–10 days, 2–3 times per cycle. Add 0.05% citric acid or 0.1% urea to improve stability and absorption.

• Special methods: Trunk injection (0.3–0.5% ferrous sulfate, 500–1000 mL/tree); fertigation with chelates at 50–100 mg/L for 2–3 hours.

  
  

  Technical Essentials

• Match product to soil: EDDHA/organic iron for alkaline soils; inorganics for acidic soils.

• Timing: Cereals at tillering and flowering; fruit trees before bud break, after fruit set, and post-harvest; vegetables at seedling and rapid growth stages.

• Compatibility: Avoid mixing ferrous sulfate with alkaline pesticides or phosphorus fertilizers; test chelated irons before large-scale mixing.

V. Global Market Structure and Trends

• Market Scale and Growth Drivers

  By 2025, the global ferrous sulfate market is valued at USD 2.52 billion and projected to reach USD 3.46 billion by 2035 at a CAGR of 3.2%. Growth is driven by:

• Prevalence of calcareous soils in Latin America/Asia-Pacific.

• Expansion of greenhouse/high-value crop cultivation demanding chelates.

• Cross-sector demand (wastewater treatment, pharmaceuticals) boosting production scale.

  
  

  Regional Characteristics

• North America & Europe: High-end chelates dominate (>60% share). Foliar use accounts for >55%, focused on fruits, vegetables, flowers.

• Asia-Pacific & Latin America: Inorganics dominate (>70% ferrous sulfate), but chelates grow fastest (5.1% CAGR). Fertilization mainly soil-based.

• Africa: Early-stage, with organic iron favored in cash crop zones.

  
  

  Technology & Market Trends

• Faster product upgrade: EDTA declining, biodegradable chelates (EDDS/IDHA) emerging.

• Precision application: Slow-release iron and functional foliar products increasing efficiency (40% vs. 15–20% traditional).

• Supply diversification: New by-product recovery technologies expanding ferrous sulfate supply; high-end chelate production shifting to Asia-Pacific.

VI. Risks and Optimization Directions

Misuse can cause iron toxicity (blackened roots, stunted growth), soil acidification/salinization, or ecological risks from chelate residues. Optimization strategies:

1. Establish “soil testing–crop diagnosis–precise formulation” systems.

2. Promote chelate + organic fertilizer co-application to stabilize iron.

3. Advance biodegradable iron fertilizer R&D to reduce environmental impact.

Conclusion

The role of iron in agriculture has evolved from basic nutrient supplementation to a comprehensive solution encompassing soil improvement, nutrient regulation, and quality enhancement. With ongoing product innovation and precision application technologies, iron fertilizers will play an increasingly critical role in supporting intensive and green agricultural development worldwide.