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Views: 0 Author: Site Editor Publish Time: 2025-12-11 Origin: Site
Micronutrients—including iron (Fe), zinc (Zn), manganese (Mn), copper (Cu), boron (B), molybdenum (Mo), chlorine (Cl), and nickel (Ni)—are required in small quantities, yet they have disproportionate effects on plant metabolism, crop health, and final yield quality. Although their total requirement is far lower than NPK and secondary nutrients, micronutrients regulate enzymatic reactions, hormone synthesis, energy conversion, reproductive development, and stress tolerance.
This article provides a detailed explanation of micronutrient functions across growth stages, deficiency and toxicity symptoms, and the advantages and disadvantages of common raw material sources.
At this phase, micronutrients support foundational processes such as chlorophyll formation, root establishment, and early metabolic activity.
Micronutrient | Key Functions at Early Stages |
Iron (Fe) | Drives chlorophyll synthesis; essential for electron transport; prevents early chlorosis. |
Zinc (Zn) | Supports auxin synthesis for root development; activates enzymes for early growth. |
Manganese (Mn) | Chloroplast formation; improves early photosynthetic efficiency. |
Boron (B) | Initiates cell wall formation; supports meristem development. |
Copper (Cu) | Promotes enzyme activation; strengthens early structural tissues. |
Molybdenum (Mo) | Required for nitrate reduction; supports early nitrogen metabolism. |
Micronutrient demand increases due to high metabolic activity and biomass expansion.
Micronutrient | Key Functions at Vegetative Stage |
Fe, Mn | Maintain chlorophyll and photosynthesis at high metabolic rates. |
Zn | Regulates leaf expansion, internode length, and protein synthesis. |
B | Enhances tissue elasticity and vascular transport. |
Cu | Supports lignification and disease resistance. |
Cl | Regulates stomatal function and osmoregulation. |
Micronutrients are critical for pollen viability, successful fertilization, and early fruit formation.
Micronutrient | Reproductive Functions |
B | Essential for pollen tube growth; prevents flower/fruit abortion. |
Zn | Supports hormone balance and carbohydrate transport. |
Cu | Enhances pollen formation and plant immunity. |
Mo | Required for nitrogen assimilation during reproductive transition. |
Micronutrients regulate sugar accumulation, color development, enzyme activity, and quality formation.
Micronutrient | Roles in Maturation |
K-related micronutrient synergy (especially Zn, B) | Improves sugar transport and fruit size. |
Fe, Mn | Maintain active photosynthesis for carbohydrate supply. |
B | Strengthens fruit cell walls; increases firmness and storage life. |
Cu | Influences color formation and disease resistance. |
Mo | Supports protein formation and seed development. |
Element | Deficiency Symptoms | Excess Hazards |
Fe | Interveinal chlorosis in young leaves; pale shoots. | Bronzing, root blackening, reduced phosphorus uptake. |
Zn | Small leaves, shortened internodes, rosetting, reduced root growth. | Stunted growth, leaf chlorosis, impaired Fe and Mn uptake. |
Mn | Mottled chlorosis; brown speckles on leaves. | Dark spots, leaf crinkling, toxicity-induced chlorosis. |
B | Brittle tissue, cracked fruit, hollow stems, flower abortion. | Leaf margin burn, leaf thickening, severe toxicity in sensitive crops. |
Cu | Leaf wilting, dieback, weak stems, poor pollen formation. | Root inhibition, leaf necrosis, reduced phosphorus availability. |
Mo | Pale leaves, nitrate accumulation, whiptail in Brassicas. | Rare toxicity; potential nutrient imbalance. |
Cl | Leaf bronzing; reduced turgor; wilting. | Leaf burn, premature leaf drop. |
Ni | Poor seed germination, leaf necrosis in legumes. | Toxicity at high levels; reduced root growth. |
Source Type | Examples | Advantages | Disadvantages |
Sulfates | ZnSO₄, MnSO₄, FeSO₄, CuSO₄ | Quick release; widely available; cost-effective. | Higher leaching; soil pH sensitivity; potential phytotoxicity. |
Chlorides | BCl₃, ZnCl₂ | Fast uptake; highly soluble. | Chloride-sensitive crops may suffer toxicity. |
Oxides | ZnO, MnO, Fe₂O₃ | Slow-release; stable in soil. | Low immediate availability; pH dependent. |
Chelate Type | Best For | Advantages | Disadvantages |
EDTA chelates | General-purpose foliar & fertigation | High solubility; stable; efficient uptake. | Moderate stability in alkaline soils. |
DTPA chelates | Slightly alkaline soils | Stronger stability than EDTA; ideal for Fe. | Higher cost. |
EDDHA chelates | Highly alkaline soils (pH > 7.5) | Most stable form for Fe; prevents chlorosis. | Expensive; limited availability for non-Fe elements. |
Source | Advantages | Disadvantages |
Borax, Colemanite (Boron) | Long-lasting, cost-effective. | Slow-release; not suitable for rapid correction. |
Pyrite-based Fe sources | Slow-release Fe for acidic soils. | Low immediate availability. |
Manganese ores | Long residual effect. | Requires microbial/chemical weathering for release. |
Source | Advantages | Disadvantages |
Seaweed extracts | Contain natural B, Fe, Zn, Mn; enhance bioavailability. | Low micronutrient concentration; not suitable for major correction. |
Humic/Fulvic complexes | Improve micronutrient mobility; enhance root absorption. | Micronutrient levels vary; variable quality. |
Amino acid chelates | High absorption efficiency; safe; ideal for foliar spray. | Higher cost; not always stable in extreme pH. |
1. Micronutrient requirements vary strongly by growth stage—especially B, Zn, Fe, and Mn.
2. Deficiencies arise mainly due to soil pH issues, leaching, and antagonism with other nutrients.
3. Chelated forms are recommended for immediate correction, particularly Fe, Zn, and Mn in alkaline soils.
4. Organic complexes are ideal for crop quality enhancement and stress resistance.
5. Toxicity risks exist, especially for B, Mn, Cu, and Cl—precise application is essential.
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