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Humic acid and fulvic acid are the two main components of soil humus. They have some significant differences in chemical properties, sources, structures and functions. Here are their main differences:

1. Source and composition

Humic Acid:

Source: Humic acid mainly comes from the decomposition and decay process of soil organic matter (such as animal and plant residues).

Composition: Humic acid is a complex macromolecule composed of a variety of organic compounds, including aromatic and fatty structures, as well as a large number of functional groups such as carboxyl, hydroxyl, phenol groups, etc.

Fulvic Acid:

Source: Similar to humic acid, fulvic acid is also a product of the decomposition of soil organic matter, but compared to humic acid, fulvic acid is a product with a higher degree of decomposition.

Composition: Fulvic acid has a smaller molecular weight, simpler structure, contains more functional groups such as carboxyl and hydroxyl groups, and has stronger solubility and mobility than humic acid.

2. Solubility

Humic acid: Limitedly soluble in water, but soluble under alkaline conditions (such as sodium hydroxide solution).

Fulvic acid: has good solubility in water, weak acid and alkaline solutions.

3. Molecular weight and structure

Humic acid: higher molecular weight, complex structure, more aromatic structures and cross-linked polymer chains.

Fulvic acid: has a lower molecular weight, a relatively simple structure, and is richer in low molecular weight organic compounds and a large number of functional groups.

4. Color and appearance

Humic acid: usually appears dark brown to black because it contains a large amount of aromatic compounds and macromolecular structures.

Fulvic acid: usually appears yellow to brown, lighter in color because it has a smaller molecule and contains more small-molecule water-soluble compounds.

5. Soil action

Humic acid: Promotes the formation of soil aggregate structure, improves soil water and fertilizer retention capacity, improves soil structure, increases soil organic matter content, has strong chelating properties, and can help fix and release nutrients.

Fulvic acid: It is more easily absorbed by plants, directly affects plant growth, promotes the development of plant root systems, enhances plant absorption of nutrients, and improves plant disease resistance and stress resistance.

6. Application areas

Humic acid: widely used in agriculture as a soil conditioner, fertilizer additive, and in industrial fields such as water treatment, forging, and ceramic manufacturing.

Fulvic acid: Due to its high solubility and biological activity, it is mainly used in agricultural fields such as liquid fertilizers, plant growth promoters, and plant nutrients, as well as in medicine, cosmetics, and environmental protection.

In short, although humic acid and fulvic acid are both important components of soil humus, they have significant differences in chemical properties, structure and function. Humic acid is mainly used to improve soil structure and fertility, while fulvic acid is more focused on directly promoting plant growth and improving plant health.