Fulvic acid has a small molecular weight, making it easily absorbed and utilized by plants. It also contains more functional groups, resulting in greater physiological activity than general humic acids and a stronger ability to complex metal ions. Humic acid is not directly soluble in water and needs to be converted into monovalent metal salts such as potassium or sodium, or ammonium salts, before it can dissolve in water. The aqueous solutions of these salts are alkaline, while fulvic acid is directly soluble in water, and its aqueous solution is acidic.
Fulvic acid is an essential component purified from plant straw and other similar materials.
The functions of fulvic acid are as follows:
Ⅰ. Water retention: As a colloidal organic substance, fulvic acid loosens the soil, absorbs a large amount of water, improves aeration and moisture retention, prevents drought, and provides favorable water, air, and heat conditions for seed germination and seedling growth.
Ⅱ. Improvement of saline-alkali soil: Due to its small molecular weight and high activity, fulvic acid can adsorb harmful cations in the soil, thereby reducing the salt concentration and minimizing the harm of salts to seeds and seedlings, thus improving saline-alkali soil.
III. Drought and Cold Resistance
1. When fulvic acid is sprayed onto plant leaves, it can close the plant’s stomata, reducing water transpiration.
2. The dark color of fulvic acid facilitates solar energy absorption; when fulvic acid is decomposed by microorganisms, it releases heat, raising the soil temperature and thus contributing to cold resistance.
IV. Pest and Disease Resistance
Fulvic acid can increase the activity of enzymes in plants, enhancing their resistance.
V. Prevention and Control of Heavy Metal Pollution
Fulvic acid participates in ion exchange reactions in the soil, adsorbing and fixing heavy metal ions, preventing them from entering the biological cycle.
VI. Improved Fertilizer Efficiency
1. Nitrogen Fixation: Nitrogen applied to the soil easily volatilizes into the atmosphere or is washed into rivers. Fulvic acid can adsorb nitrogen in the soil, reducing its volatilization and loss, thus improving its utilization rate.
2. Phosphorus Solubilization: Phosphorus applied to the soil is easily fixed by the soil. Fulvic acid can chelate phosphorus, releasing it from the soil for plant absorption, thus improving phosphorus utilization. 3. Potassium Activation: Most potassium applied to the soil exists in the form of potassium salts and cannot be directly absorbed by crops. Fulvic acid can convert insoluble potassium into soluble potassium through ion exchange, increasing the available potassium in the soil and improving potassium utilization.
4. Micronutrient: Fulvic acid can chelate with insoluble micronutrients to form humic acid-micronutrient chelates that are easily absorbed by crops, thus facilitating the absorption of micronutrients by roots and leaves.
VII. Promoting Crop Growth and Development
1. Fulvic acid stimulates root growth, ultimately leading to a significant increase in the crop’s ability to absorb water and nutrients.
2. The stimulating effect of fulvic acid promotes vigorous growth of the above-ground vegetative parts of the plant, manifested in plant height, stem thickness, and leaf thickness.
3. Fulvic acid has a good effect on tillering and reducing empty grain rate, increasing the thousand-grain weight of grain and thus increasing grain yield.
VIII. Regulating Soil pH: Fulvic acid has numerous functional groups, allowing it to bind with both acids and alkalis, thus regulating soil pH according to crop needs.
IX. Why Does Fulvic Acid Improve Agricultural Product Quality?
Fulvic acid enhances the synthesis and transport of sugars, starches, proteins, fats, and various vitamins by enzymes. It can stimulate the activity of polysaccharide enzymes, converting polysaccharides into soluble monosaccharides, thereby increasing fruit sweetness; it increases the ratio of total sugar to nicotine and potassium to chlorine in tobacco leaves, improving tobacco quality; and it increases the total sugar content and vitamin C content in melons such as watermelons and cantaloupes.
1. Regulating Enzymatic Reactions and Enhancing Plant Life Activities: Enzymes are biological catalysts for plant life activities, and the extent of their effect is expressed by their activity. Fulvic acid can stimulate the activity of polysaccharide enzymes, causing the hydrolysis of pectin in the cell walls of young cells, softening the cell walls, and making cells easier to elongate and divide, growing both longitudinally and laterally. Therefore, it has a significant effect on promoting the growth of new tissue and young cells, especially on the root meristem.
Fulvic acid contains a large number of carboxyl groups, which can inhibit the activity of auxin oxidase, reducing auxin degradation and increasing its content. This promotes root and stem growth, resulting in faster root development, more secondary roots, increased root mass, and longer root systems, thus enhancing the crop’s ability to absorb water and nutrients.
Fulvic acid can promote the activity of invertase, starch phosphorylase, and some enzymes related to protein and fat synthesis, increasing the synthesis and accumulation of sugars, starches, proteins, fats, nucleic acids, vitamins, and other substances. It also promotes the activity of transferases, accelerating the transport of various metabolites from stems, leaves, or roots to fruits and grains, directly impacting crop yield and quality.
2. Increases chlorophyll content and promotes photosynthesis. Fulvic acid promotes the absorption and transport of micronutrients in plants, significantly increasing chlorophyll content in leaves. It also inhibits the activity of proteolytic enzymes, slowing down chlorophyll decomposition.
Fulvic acid can increase the activity of protective enzymes, reducing the damage of chlorophyll caused by reactive oxygen species. These factors all contribute to maintaining and increasing chlorophyll content, promoting photosynthesis, and enhancing the accumulation of photosynthetic products.
3. Enhancing Respiration: Fulvic acid enhances the activity of respiratory enzymes, particularly terminal oxidases, thereby strengthening respiration. This leads to the continuous release of energy and the production of numerous intermediate products, providing the plant with the resources for its life activities. Increased respiration promotes root absorption and nutrient synthesis.
4. Promoting the Absorption and Transport of Mineral Elements: Many trace mineral elements, such as Fe, Cu, Zn, Mn, B, and Mo, are components of enzymes or coenzymes involved in plant metabolism, or significantly influence the activity of various enzymes and plant stress resistance. Some are even components of cellular structural substances.
Fulvic acid can form soluble complexes (chelates) with mineral elements in the soil. This effect of fulvic acid enhances the absorption of many trace elements by crops.
