Differences between humic and fulvic acids
- Humic acid: Larger molecular weight fraction, dark brown to black in color, soluble in alkaline pH; primarily improves soil physical aggregation, water-holding capacity, and soil microbial activity.
- Fulvic acid: Smaller molecular weight fraction, light golden-yellow in color, completely soluble across all pH levels; highly bio-active, penetrating plant leaf cuticles easily for rapid foliar mineral chelation.
- Natural chelation: Both fractions bond with iron, zinc, copper, and manganese, preventing them from becoming fixed in alkaline or calcareous soils.
Agronomic benefits on root architecture and stress tolerance
Applying humic substances stimulates the production of lateral root hairs and root biomass by up to 25% to 40%. This expanded root architecture enhances water and phosphorus uptake, helping crops withstand drought stress, transplanting shock, and soil salinity.
Application methods and dosage guidelines
Humic substances can be applied as seed treatment (5 to 10 ml/kg seed), soil drenching or basal broadcast (potassium humate granules at 2 to 5 kg per acre), or drip fertigation and foliar spray (liquid formulations at 2 to 3 ml per litre of water). Always maintain adequate soil moisture.
Official source
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ICAR - Indian Institute of Soil Science (IISS) ↗Related on KisanPe
Common questions
What is the primary difference between humic acid and fulvic acid?
Humic acid has a larger molecular size and works primarily in soil, while fulvic acid has a smaller molecular size and works effectively as a foliar spray.
How does humic acid improve soil fertility?
It increases soil cation exchange capacity (CEC), enhances water retention, and chelates micronutrients to make them absorbable by roots.
Can humic acid be applied through drip irrigation?
Yes, water-soluble potassium humate and liquid humic formulations are widely applied through drip irrigation systems.
General guidance, not personal advice. For your farm, ask your local Krishi Vigyan Kendra or agriculture officer.
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