Humic acid and soil microorganisms
Soil is alive, and that life is soil microorganisms. As we all know, soil is the home base of microorganisms and a natural medium for their growth and reproduction. Humic acid runs through the life of the soil and is the "nucleus of life" of the soil. Without humic acid, the soil will lose its activity. Accordingly, clarifying the relationship between "soil - humic acid - microorganisms" is of great practical significance for the protection of national resources and the promotion of sustainable soil production.
1 Soil humic acid
(1) The essence of soil life.
Humic acid is a profound "dark matter" in soil, and every cycle of its life is related to the living organisms. (1) according to the living organisms: mainly to animal and plant residues (mainly plant residues) as a source of material; (2) through the transformation of the living organisms: mainly through the participation of microorganisms and the role of continuous decomposition, transformation, synthesis; (3) the return to the living organisms: mainly through the soil humic acid feeds the living organisms to promote the growth of green plants (producers) to enhance the livestock, poultry, aquatic animals and people (consumers), etc. *********, as the microorganisms (decomposers) to provide nutrients and energy sources. Accordingly, humic acid accompanies the rhythm of life, realizing the cycle of "survival → transformation → extinction → rebirth", and becomes the original source of soil vitality according to its existence.
(2) The nucleus of soil structure.
Soil structure characteristics include three meanings: ① in the process of soil formation, organic matter and minerals to form organic - inorganic complex, micro-aggregates, macro-aggregates, etc.; ② micro-aggregates is the core of the soil structure, is the soil to play its function **** small, independently existing structural units (equivalent to the cells in the soil); ③ soil structure in the process of soil utilization of soil function has a great impact on the soil. Throughout the above three items, of ② microaggregates is the "soil house" the key to the stability of the structure, and humic acid is the construction of soil "micro-house" key components. In the process of soil formation, humic acid and a variety of microbial secretion of polysaccharide aldehyde acid glycosides and other organic macromolecules, viscous minerals and iron, aluminum hydroxide, etc., through different forms and a variety of forces combined to form a variety of organic and inorganic complexes. At the same time, under various surface charges and forces, microagglomerates of different particle sizes are formed through agglomeration. Accordingly, the formation process of microaggregates of humic acid gives the soil organic and inorganic complexes vivid vitality, and is the core and key to stabilize the soil structure.
(3) The importance of soil function.
Soil ecosystem function mainly includes: the ability and level of material transformation and energy circulation in soil, the activity of soil organisms, the balance of nutrients and water in soil and its impact on the environment. Humic acid is the *** active part of soil organic matter, and plays a vital role in the material circulation and energy conversion of soil ecosystem: ① active participant and promoter of soil formation and soil fertility; ② promotes and restricts the migration, fixation and leaching of soil metal ions and trace elements; ③ is the stabilizer of soil structure; ④ influences the soil's capacity of saline exchange; ⑤ influences the water-holding capacity of soil; ⑥ is the storehouse of plant materials. ⑥ is a storehouse of plant materials. Accordingly, humic acid can regulate the material cycle, energy conversion and information transfer between biological system, soil system and environmental system, and is an important substance to maintain the stability of soil function.
2 Soil microorganisms
(1) Soil microbial composition.
Soil is the base camp of microorganisms, is the natural "medium" for microbial growth and reproduction. Soil microorganisms are the general name of ******, ******, actinomycetes, algae, etc. living in the soil, which is an important component of the soil. Their individuals are tiny, generally calculated in microns or millimeters, and their types and numbers vary with the soil-forming environment and the depth of the soil. Among them, there are more *********, followed by actinomycetes and ******, and fewer algae. It is estimated that there are thousands or even tens of thousands of species, about hundreds of millions to billions of individual microorganisms per gram of soil, and their species and numbers vary with the soil-forming environment and the depth of its soil layers. Generally speaking, in each gram of soil in the tillage layer, the number of ****** is about 10^8 to 10^9, the number of actinomycetes is about 10^7 to 10^8, the number of ****** is about 10^5 to 10^6, and the number of algae is about 10^4 to 10^5, and they all reside in the soil.
(2) Soil microbial action.
Soil microorganisms have a significant impact on soil formation and development, material cycling, fertility evolution, and plant growth. (1) ******: Suitable for neutral and slightly alkaline living conditions. Among them, autotrophic ****** have the ability to assimilate carbon dioxide, directly affecting the physical and chemical properties of the soil, balancing the pH level of the soil; heterotrophic ****** exist in a symbiotic state with the crop, and have a direct role in promoting the growth of crops, such as legume rhizobacteria, and so on, with a strong nitrogen fixation, in the case of less nitrogen fertilizer to produce a significant increase in yield. ② Actinomycetes: suitable for neutral and slightly alkaline living conditions. Actinomycetes in the soil are living in aerobic heterotrophic state, their main activity is the decomposition of cellulose, lignin and pectin-like substances in the soil, etc., and through these roles to improve the nutrient status of the soil, to facilitate the direct absorption of crops to utilize soil nutrients. ③******: Suitable for slightly acidic living conditions. It participates in the decomposition of animal and plant residues, and becomes an indispensable driving force for nitrogen and carbon cycles in the soil. Especially in the early stages of decomposition of plant organisms, ****** is more active than ****** and actinomycetes. ④ Algae: a class of unicellular organisms, mainly found in aquatic environments. The blue ****** in algae also has the role of fixing nitrogen in the air. It is more suited to function in alkaline environments.
(3) Soil microbial vitality.
Soil microorganisms are not only an important part of the soil, but also the vitality of the soil ecosystem. ① all kinds of microbial metabolism of gas and organic acids, etc., to help the formation of soil granular structure; ② decomposition of organic matter, synthesis of soil humus - humic acid, fertilization of the soil; ③ decomposition of minerals, to promote the dissolution of insoluble substances in the soil (eg, phosphorus ******, potassium ******, etc.); ④ fixation of atmospheric nitrogen, increase the nitrogen nutrients in the soil; ⑤ regulation of plant growth, such as symbiosis with plant rhizobium, mycorrhiza, ******, etc.; ⑥ secretion of ********* (such as actinomycetes), to prevent soil-borne diseases; ⑦ secretion of a large number of enzymes, to promote the transformation of soil nutrients; ⑧ degradation of residual organic pesticides, urban pollutants in the soil and factory waste, etc.. The above eight items, reflecting the important relationship between soil microorganisms and soil fertility, soil health, plant growth, is the soil ecosystem material cycle and energy flow of the main force.
3 Soil humic acid and microorganisms
(1) Microbiological mechanism of soil humic acid formation.
There are mainly seven hypotheses about the microbiological mechanism of humic acid formation: ① Waxman's theory that, in the process of plant to humus formation, nitrogenous organic matter and nitrogen-free organic matter through aerobic microbial decomposition to produce microbial bodies (soil proteins) and lignin, and the two combined with alkalis to form humus. ② Williams theory that humic acid is the secretion of soil microorganisms; ③ microbial synthesis hypothesis that microorganisms use plants as a carbon source and energy source, and can synthesize macromolecular humic substances within the cells, which are released into the soil after the death of microorganisms, and then degraded outside the cells to humic acid and xanthic acid; ④ cellular autolysis hypothesis that humus is a cellular autolysis product of the plants and microorganisms after their deaths; ⑤ the coal chemistry theory that According to the coal chemistry theory, there are two main conditions affecting the accumulation of plant residues and the formation of peat in swamps, one is the physical condition of isolating plant residues from the air, and the other is the chemical condition of maintaining the good activities of microorganisms; (6) According to the Kononova theory, the formation of humus consists of two stages of decomposition and condensation, both of which involve soil microorganisms; and (7) The cell autolysis hypothesis holds that humus is a product of cell autolysis after the death of plants and microorganisms. All have the participation of soil microorganisms; (7) anaerobic fermentation theory that humic acid formation includes "hydrolysis-acid production-synthesis" three stages, with varying degrees of microbial role. Regardless of which hypothesis, all fully affirmed the important role of microorganisms in the process of humic acid formation.
(2) Effectiveness of humic acid in soil microbial reproduction.
The formation of humic acid is inseparable from soil microorganisms, and the reproduction of soil microorganisms is also inseparable from humic acid. Humic acid provides material and energy sources for soil microorganisms. Soil microbial nutrition mainly includes carbon, hydrogen, oxygen, nitrogen and some mineral elements. Humic acid contains carbon, oxygen, hydrogen, nitrogen and other elements, can provide soil microorganisms with carbon and nitrogen sources for their survival and reproduction. ② Humic acid creates a suitable living environment for soil microorganisms. Soil microorganisms need to survive the appropriate temperature, humidity, pH and so on. Humic acid can directly or indirectly improve the soil temperature, moisture and air permeability, regulate soil pH, promote the growth and reproduction of soil microorganisms, and increase their number and variety. ③ Humic acid provides a home for soil microorganisms to survive. The total number of microorganisms is also higher in soils with deep soil layers, loose soil texture, better physical properties and richer effective nutrients. Humic acid is the core of soil fertility, humic acid Xing soil fertilizer Xing; soil fertilizer Xing, the microbial Xing.
(3) Humic acid and microorganisms are the same as the soil life community.
Humic acid is the bearer of soil life, providing carbon and nitrogen sources for microorganisms and accompanying them for life, and promoting the number, variety and diversity of microorganisms; microorganisms are the embodiment of soil life, playing the role of decomposer, and are indispensable to the formation and decomposition of humic acid. The formation of humic acid is inseparable from soil microorganisms, the survival and reproduction of soil microorganisms are inseparable from humic acid, and the two are interdependent, jointly promoting the formation and development of the soil, the evolution of fertility, material cycle and energy transformation. It can be seen that "soil - humic acid - microorganisms" are inseparable, belonging to the life community.
4 Conclusion
At present, the global soil life tolerance is close to the limit, 70% of our soil has obstacles. Redeeming soil life and restoring soil vitality has become an important task for human beings. We hope that all "humic acid people" will consciously take up the task of "soil maintenance revolution", vigorously carry out the action of "saving a gram of soil for the sake of millions of people", and make a great effort to maintain soil health and vitality through humic acid fertilizer and its derivatives. Through the return of humic acid fertilizer and its derivatives, we will make significant contributions to the maintenance of soil health and sustainable agricultural production.