Essential plant micronutrients and their physiological functions
While required in small amounts compared to primary macronutrients, micronutrients are equally vital for completing a crop's reproductive lifecycle.
Intensive cropping with high-yielding varieties and unbalanced NPK fertilization has exhausted native micronutrient reserves across major Indian agro-climatic zones.
- Zinc (Zn): Crucial for tryptophan synthesis (precursor to growth hormone auxin), internode elongation, and enzyme activation; prevents khaira disease in rice.
- Boron (B): Essential for pollen tube germination, cell wall development, sugar transport, and fruit setting; prevents fruit cracking and hollow heart.
- Iron (Fe): Indispensable for chlorophyll synthesis and electron transport; corrects interveinal chlorosis in calcareous soils.
- Manganese (Mn) & Copper (Cu): Act as cofactors in photosynthesis, respiration, and lignin synthesis for stalk strength.
Approved straight and multi-micronutrient formulations
Under Schedule I of the Fertilizer Control Order (FCO), state-specific micronutrient grades and straight chemical salts are regulated for quality and purity.
Formulations are available as soil-applied inorganic salts, chelates (such as Zn-EDTA and Fe-EDTA), and water-soluble foliar mixtures.
- Zinc Sulphate: Available as Heptahydrate (21% Zn) and Monohydrate (33% Zn) for soil application and foliar spraying.
- Borax & Disodium Octaborate Tetrahydrate (DOT): Soluble boron sources for soil broadcast and rapid foliar absorption.
- Chelated micronutrients (EDTA): Protect metal cations from soil fixation, ensuring high nutrient-use efficiency at lower dosage rates.
- State-specific multi-micronutrient grades: Customized mineral mixtures formulated according to district-level soil deficiency mappings.
Soil testing, application methods, and deficiency correction
Micronutrient application must always be guided by laboratory soil testing or foliar tissue analysis to avoid toxic over-fertilization.
Soil application provides long-term residual correction, while foliar spraying provides rapid therapeutic remediation of visible crop deficiencies.
- Soil Health Card: Consult your Soil Health Card to determine specific micro-element deficiency levels before purchasing fertilizers.
- Soil application timing: Broadcast basal micronutrients mixed with compost or sand; avoid direct contact with concentrated soluble phosphorus.
- Foliar spray timing: Apply chelated or neutralized micronutrient solutions during early vegetative growth or prior to flowering.
Official source
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Soil Health Card Portal, Ministry of Agriculture ↗Related on KisanPe
Common questions
What are the primary micronutrients required by agricultural crops?
The essential micronutrients are Zinc, Boron, Iron, Manganese, Copper, Molybdenum, and Chlorine.
Why is Zinc critical for paddy and maize crops?
Zinc prevents khaira disease in paddy and white bud in maize, driving growth hormone (auxin) synthesis and vigorous tillering.
What is the difference between chelated and inorganic micronutrients?
Chelated micronutrients (like Zn-EDTA) are organically bound, preventing them from reacting with soil minerals and ensuring higher plant uptake.
General guidance, not personal advice. For your farm, ask your local Krishi Vigyan Kendra or agriculture officer.
More Fertilizers & Crop Nutrition guides
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