Lignosulfonate and humic acid are both dark, lignin-related organic materials, but they come from different sources and behave differently. Lignosulfonate is a water-soluble sulfonated lignin from wood pulping, used mainly as a dispersant, binder and micronutrient carrier. Humic acid comes from decomposed organic matter such as leonardite or lignite; it is insoluble in acid, soluble as potassium or sodium humate, and used mainly as a soil amendment.
Comparison
| Property | Lignosulfonate | Humic acid / humates |
|---|---|---|
| Source | Sulfite pulping of wood or other biomass | Leonardite, lignite, peat, compost |
| Formation | Industrial sulfonation of lignin | Natural humification over long periods |
| Main functional groups | Sulfonate, phenolic hydroxyl, some carboxyl | Carboxyl and phenolic hydroxyl |
| Solubility | Soluble in water across the pH range, including acidic solutions | Humic acid insoluble below about pH 2; soluble as K or Na humate in alkaline solution. Fulvic acid is soluble at all pH |
| Behaviour with hard water / calcium | Stays in solution (sulfonate groups) | Humates can precipitate with calcium and magnesium |
| Main agricultural roles | Dispersant, binder, wetting aid, micronutrient complexing agent | Soil amendment, biostimulant ingredient, carrier |
| Typical products | Ca, Na, NH4, K and micronutrient lignosulfonates | Humic acid, potassium humate, fulvic acid |
Where Each Fits in a Fertiliser Programme
- Formulation work (suspensions, granules, liquid micronutrients): lignosulfonate, because it disperses, binds and stays soluble in acidic and hard-water conditions.
- Soil amendment programmes: humates and fulvic acid are the more common choice; claims on soil structure or nutrient uptake should be supported by local trials.
- Combined products: lignohumates combine lignin-derived material with humic-like fractions. See the lignohumate products in the agricultural range.
- Liquid blends with calcium: lignosulfonate is usually the safer carrier; humates may flocculate. Confirm with a jar test.
Common Misunderstandings
- Lignosulfonate is not a humic substance, even though both are dark brown and lignin-related.
- High “organic matter” on a data sheet does not mean the same function: a lignosulfonate and a humate with the same organic content behave differently.
- Fulvic acid is a different fraction from humic acid: smaller and soluble at all pH.
Frequently Asked Questions
Is lignosulfonate the same as humic acid?
No. Lignosulfonate is sulfonated lignin from wood pulping; humic acid is formed by natural decomposition of organic matter and is extracted from materials such as leonardite.
Can lignosulfonate and humic acid be mixed?
Often yes, but humates can precipitate in acidic or calcium-rich mixes. Check with a jar test before use.
Which is better for micronutrient fertilisers?
Lignosulfonate is the more common carrier for liquid micronutrient complexes because it stays soluble across a wide pH range and in hard water.
Related Pages
Questions about a specification, a test method or a trial: contact us or email info@greenagrochem.com.
