Humic acid

Humic acid (CAS 1415-93-6), also referred to as HA, is a naturally derived organic acid extracted from leonardite, lignite, or peat.

Where is Humic acid used?

• Agriculture: chelating agent, pH buffer, and soil conditioner
• Crop nutrition: chelates micronutrients such as iron, zinc, and manganese, improving uptake efficiency and reducing fertilizer lock-up in alkaline soils
• Soil drenches or foliar sprays stimulate root development and enhance nutrient retention in the rhizosphere
• Water treatment: coagulation and flocculation aid that aggregates suspended solids and organic matter for easier removal
• pH regulation: buffering capacity stabilizes process water or irrigation inputs
• Improves soil structure by binding soil particles into aggregates.
• Used as a sorbent in water treatment.
• Limits leaching of cations such as Ca2+, Mg2+, K+ and NH4+.
• Used for filtrate control and deflocculation in water-based drilling muds.

Good to know: Solubility and active content vary by source material and extraction method, so buyers typically specify minimum humic acid percentage, often alongside potassium humate or sodium humate salt form where applicable.

Formulation notes

• In tank mixes below pH 6, it will clump and clog sprayers.
• Granular humic acid is applied at 30 to 60 kg per hectare, split over the annual cycle, incorporated into the soil before vegetative activity or before sowing/transplanting.
• Liquid humic and fulvic acid blend is applied by fertigation in horticultural and herbaceous crops at 5 to 8 liters per hectare per irrigation from transplanting to end of cycle.
• Raw lignite-derived humic acid is soluble only in alkaline solutions, while reaction with potassium yields 93–98% water-soluble granules and flakes.

Typical specification

• Sold in granular form with a 2–4 mm particle size.
• The standard lignite humic acid granule grade has 93% water solubility.
• Liquid humic acid typically has a humic acid concentration of 8–20% and is highly bioactive.
• Humic acid from leonardite is reported to have a cation exchange capacity of about 350 to 450 meq/100 g.

Regulatory status

• For EU shipments, cadmium results must comply with the limits of Regulation (EU) 2019/1009.
• Heavy metals (arsenic, cadmium, lead) must be analyzed because leonardite is a coal-derived material.

Frequently asked questions about Humic acid

How does the test method affect the reported humic acid percentage?

Humic acid percentage depends on the test method, so the same lot can read 70% by one method and 45% by another.

What are the solubility characteristics of humic acid?

Humic acid is soluble in alkali and precipitates in acid.

What should be done before mixing humic acid with other products?

A jar test should be conducted before mixing with other products, and combining humic acid with other inputs may require prior validation to avoid flocculation, precipitation or loss of efficacy.

Technical content is compiled and updated by the SoleChem product team from public technical sources; the certificate of analysis (COA) governs product-specific specifications.