Microbial inoculants refer to viable bacterial preparations made by industrialized cultivation, propagation, and processing, with specific functional microorganisms as the core component. Their key ingredients are beneficial microorganisms with clear physiological functions (e.g., bacteria, fungi, actinomycetes), supplemented by carriers (such as peat, vermiculite, humic acid) to ensure the survival and activity of microorganisms.

The core characteristics and classifications of microbial inoculants are as follows:

1. Core Characteristics

    - Live Microorganism Dominance: The key quality indicator of the product is the number of effective viable bacteria, which must comply with relevant national standards (e.g., Agricultural Microbial Inoculants GB 20287-2006). It shall not contain pathogenic or harmful microorganisms.

    - Functional Specificity: Different strains correspond to different functions. For example, nitrogen-fixing bacterial inoculants are used to supplement nitrogen; phosphorus- and potassium-solubilizing bacterial inoculants are used to activate insoluble phosphorus and potassium in soil; and biocontrol bacterial inoculants are used to inhibit soil-borne diseases.

    - Environmental Friendliness: They contain no chemical nutrients per se and exert their effects through the life activities of microorganisms, causing no soil pollution or nutrient residues.

2. Common Classifications

    - By microbial species: They can be divided into bacterial inoculants (e.g., rhizobial inoculants, bacillus inoculants), fungal inoculants (e.g., trichoderma inoculants, mycorrhizal fungal inoculants), and actinomycete inoculants (e.g., streptomycete inoculants).

    - By function: They can be divided into nitrogen-fixing inoculants, phosphorus-solubilizing inoculants, potassium-solubilizing inoculants, disease-resistant and growth-promoting inoculants, and degrading inoculants (used for soil pollutant remediation).

    - By formulation: They can be divided into liquid inoculants, powder inoculants, and granular inoculants. Different formulations are suitable for application scenarios such as seed dressing, root irrigation, and broadcasting.

3. Differences from Bio-organic Fertilizers

    Microbial inoculants take functional microorganisms as the sole core, containing no or only a small amount of organic nutrients. In contrast, bio-organic fertilizers are composites of functional microorganisms + decomposed organic materials, which have both microbial activity and the nutrient supply capacity of organic fertilizers.