Six effects of humic acid on crops.Humic acid is an organic substance with amorphous reticular structure formed by the decomposition and transformation of animal and plant remains and a series of chemical processes. Mainly includes carbon, hydrogen, oxygen, nitrogen and sulfur, with molecular weights ranging from hundreds to tens of thousands or even millions. It is considered that humic acid is more likely to exist in supramolecular state in soil. Humic acid has high physicochemical activity, physiological activity and optical activity. Which further determines the multifunctional application of humic acid in the field of plant protection.

1. Stimulation of physiological metabolism

Humic acid contains a variety of active functional genes. Which can enhance the activity of catalase and polyphenol oxidase in crops. Stimulate physiological metabolism and promote growth and development. For example humic acid can promote early germination of seeds and high emergence rate especially at low temperature. It can stimulate the division and growth of root extreme meristem cells and make seedlings grow faster. Increase more roots and make root extension. Thus improve the ability of crops to absorb water and nutrients. Therefore, the supply of nutrients is sufficient.  The stems of crops grows fast and strong.  The branches and leaves are luxuriant. Photosynthesis is enhanced. The transfer of nutrients to fruiting bodies is accelerate. And fruits are colored and mature in advance.

2.Increasing plant resistance

Six effects of humic acid on crops.Humic acid can increase plant resistance to drought, cold, salt and alkali and diseases and insect pests. Which is closely related to plant protection work is closely related to the improvement of plant disease and insect pest resistance.  Which is mainly achieved by humic acid affecting plant growth. Good plant growth will improve its own immune resistance function.  Which is the internal basis of plant disease prevention and resistance.

Humic acid can reduce stomatal opening intensity of plant leaves.  Reduce leaf transpiration. Thus the water consumption is reduced.  Then improve the water status of plants. Ensure the normal growth and development of crops under drought conditions.  Enhance drought resistance. Humic acid is mostly amphoteric colloid, which has high surface activity and has inhibitory effect on fungi. It can enhance the cold resistance of crops. Easy to be adsorbed by cell membrane. Change the permeability of cell membrane. Promote the absorption of inorganic nutrients.  Prevent rot disease, root rot disease and reduce diseases and insect pests.

Humic acid itself has a similar hormone effect on plants. Directly absorbed by plant cells to affect plant growth. And humic acid can affect plant growth and improve plant resistance to diseases and insect pests by affecting cell membrane activity. Some studies have shown that humic acid (LMS < 3500Da) with small molecular weight can directly enter the protoplast through the cell membrane.  The humic acid (HMS > 3500Da) with large molecular weight can not pass through the cell membrane.  But it can affect the properties of the cell membrane, thus affect the absorption of nutrient elements.Humic acid may also have a negative effect on plants. Such as high concentration of current inhibition of plant growth.  Increase the sensitivity of plant roots to pathogens. So in the use process, do not casually increase the dose, according to the recommended normal use!

3. Change the characteristics of Chemical Fertilizer

Humic acid contains carboxy, phenolic hydroxyl and other functional groups, which has strong ion exchange and adsorption capacity, which can reduce the loss of ammonium carbonate nitrogen and improve the utilization rate of nitrogen fertilizer. Nitro humic acid degraded by oxidation can inhibit the activity of urinary enzyme and reduce the volatilization of urea. The degraded nitrohumic acid increased the distance of phosphorus movement in the soil, inhibited the fixation of water-soluble phosphorus in the soil, transformed available phosphorus into slow release  available phosphorus, and promoted the absorption of phosphorus by roots. Humic acid functional groups can absorb and store potassium ions, make potassium fertilizer decompose slowly, increase potassium release amount, and increase the content of available potassium. Humic acid and insoluble trace elements can react with each other to form humic acid trace elements chelate which can be absorbed by crops with good solubility, and is beneficial to root and leaf absorption of trace elements.

4. Improve soil texture

Humic acid can promote the formation of the crumb structure of the soil, adjust the PH of the soil, adjust the soil water, the fertilizer, the air and the heat condition, improve the soil exchange capacity, reach the acid-base balance, improve the water retention and fertilizer-keeping capacity of the soil, promote the activity of the soil microorganism, and enable the quantity of the aerobic bacteria, the actinomycetes, the cellulolytic bacteria is increased, the decomposition and transformation of the organic substances are accelerated, the release of the nutrient elements is promoted, and the nutrition of the crops is facilitated.

Six effects of humic acid on crops.5. Improve fruit quality

Humic acid can form complex or chelate with trace elements, increase the amount of trace elements moving from root to leaf or other parts, regulate the proportion and balance of constant elements and trace elements, and strengthen the synthesis and transportation of sugar, starch, protein, fat and various vitamins by enzymes. It can promote the activity of enzyme, transform polysaccharide into soluble monosaccharide, increase the synthesis and accumulation of starch, protein and fat substances, accelerate the primary products of various metabolism transformed from stem, leaf or root to fruit and seed, and make the fruit havrest and good quality.

6. Optimizing farmland ecosystem

Humic acid can affect farmland ecosystem in many ways. On the one hand, it can optimize the physical and chemical properties of soil and regulate soil acidity and alkalinity and ion environment. Humic acid promotes the formation of large particle size aggregates and microaggregates in soil through flocculation and sol, then improves the structure and properties of soil. Meanwhile, humic acid itself has weak acidity, which can regulate soil acidity and alkalinity and adsorb soil anions. On the other hand, humic acid positively affected soil microorganisms, and the results showed that humic acid could obviously improve the activity of soil microorganisms.
At present, the application forms of humic acid in agriculture are humic acid fertilizer, pesticide, plastic film, soil conditioner, drought resistance agent and humic acid seedling matrix, among which humic acid fertilizer is the most closely combined with plant protection. It has the function of preventing and controlling diseases and insect pests, and stimulating and regulating crop growth.