Humic substances comprise the major organic components of soil and are produced when organic matter biodegrades, providing nutrients for plant growth. Among humic substances, fulvic acids provide supplemental plant nutrition while helping maintain soil moisture. Humic substances are complex molecular groups, formed by aromatic fenolic compounds and cycled nitrogen and aliphatic compounds, then synthesized by microorganisms present in the biomass. In short, humic substances are decomposed plant and other organic matter that provide much of the nutrients in soil. These nutrients form when organic matter in the soil – carbon hydrates, lignin, aliphatic organic acids, alcohols, aldehydes, resins, nitrogen compounds, carbon hydrates (cellulose, hemicellulose), lignin and tannins – decompose through the process of humification, forming humus, which in turn mineralize into more stable humic extracts. These extracts make the soil more fertile. Humic substances are categorized in two groups: humic acids and fulvic acids. These compounds react chemically in the soil, enabling plant assimilation of nutrients.
Difference between fulvic acids and humic acids:
- Are brown-yellow in color.
- Have a low molecular weight: 500 – 5,000 Dalton.
- Are highly soluble in acid and alkaline substances.
- Demonstrate excellent capacity of cationic exchange.
- Leave no residues.
- Generate high assimilation of elements.
- Are typically recommended for foliar and soil applications.
Formulations at 100% of fulvic acids are possible from vegetable sources rich in polysaccharides.
- Are dark brown in color.
- Have a high molecular weight: 50,000 – 300,000 Dalton.
- Are soluble in alkaline substances.
- Have good capacity of cationic exchange.
- Leave high amount of residues.
- Demonstrate a physical-chemical action in the soil.
- Are typically recommended for soil applications.
Formulations of humic acids at 100% are not possible.
Benefits of fulvic acids
- Increases the microbiological activity in the soil.
- Improves the physical, chemical and biological characteristics in soil.
- Improves the availability and take up of soil nutrients.
- Reduces salt levels in the soil.
- Have a chelating effect in micronutrients.
- Are excellent in transporting nutrients from the root to the plant.
- Permeate cellular membranes helping assimilation.
- Promote seed germination.
- Increase systemic resistance in the plants.
- Enhance flowering and fructification.
- Improve overall crop quality.
- Have excellent capture power of soil cations, unblocking insoluble forms, improving availability for plants.
- Fix ammonia, reducing the de-nitrification process and increasing the fixing capacity and assimilation of nitrogen.
- Unblock phosphorous insoluble components, making them more available for the plant.
- Provide excellent transport of macro and micronutrient absorption by the plant, transporting to the aerial part of the plant, balancing nutrition equilibrium.
- Form organic complexes with herbicides, fungicides, and insecticides, which then strengthen and increase range and efficiency.
- Modify soil structure in salty soils, increasing the cationic exchange.
- The absorbent radicals of colloidal naturally gather minerals, avoiding dispersion which helps prevent compaction and increase air in the soil. While interacting with clay and other minerals, this helps nutrients assimilate.
- Stabilizes soil structure, improving the conditions for root development and nutrient uptake.
- Increases root formation.
- The lower molecular weight of fulvic acids enables them to penetrate easily in vegetal cells, while the humic acids stay on root surfaces. This allows higher absorption by the roots and better movement inside the plant of metallic fulvates from humates.
- Modifies the plasmatic structure of cells, influencing the enzymatic processes and forming metabolic complexes that facilitate plant translocation.
In summary, soil nutrients and fertilizer assimilate better, increasing mobilization and participation of metabolic processes.