Optimal Timing for Adding Microbial Inoculants in Bio-organic Fertilizer Production Lines

In bio-organic fertilizer production, microbial inoculants are the core driving force for the decomposition and transformation of organic matter. The timing of their addition directly determines the fertilizer's maturity, nutrient conversion rate, and final fertilizer efficacy. In conjunction with the core processes of the bio-organic fertilizer production line, the optimal timing for adding microbial inoculants must be precisely matched to the material state and process nodes to avoid loss of inoculant activity or inefficient use due to improper timing. Simultaneously, the bio-organic fertilizer equipment should be used to ensure the inoculants achieve maximum effectiveness.

The raw material pretreatment stage is the "preparation period" for adding microbial inoculants, but it is not the optimal time. During this stage, raw materials such as straw and livestock manure need to be crushed, and the carbon-to-nitrogen ratio (C/N 25-30:1) and moisture content (55%-60%) need to be adjusted. If microbial inoculants are added at this time, the material has not yet reached the suitable environmental conditions for microbial survival, and subsequent mechanical operations such as stirring and crushing will damage the inoculant cells, leading to a significant reduction in the number of viable bacteria.

The initial fermentation stage is the golden period for adding microbial inoculants, specifically within 12-24 hours after the raw materials are evenly mixed and placed in the fermentation tank (or fermentation pile). At this stage, the material temperature is within the mesophilic range of 25-35℃, and indicators such as the carbon-to-nitrogen ratio and moisture content have met the standards. The material also contains sufficient oxygen, perfectly meeting the germination requirements of aerobic functional microorganisms (such as Bacillus and Actinomycetes). Evenly spraying or mixing the microorganisms into the material allows them to quickly adapt to the environment and multiply rapidly, seizing ecological niches and inhibiting the growth of harmful microorganisms such as putrefactive bacteria, laying the foundation for subsequent high-temperature fermentation.

If additional microorganisms are needed during fermentation, it should be added during the "secondary fermentation period" when the temperature has dropped below 40℃. The high-temperature fermentation stage (55-65℃) will kill some of the initial microorganisms. When the temperature naturally drops to the mesophilic range, adding heat-resistant or functionally complementary microorganisms can further improve the material's maturity and enhance the fertilizer's disease resistance and growth-promoting functions. It is important to avoid adding microorganisms at the peak of the high-temperature period, as the high temperature will cause the microorganisms to become inactive.

The addition of microbial inoculum is not recommended during the post-processing stages (drying, granulation, and packaging). The high-temperature drying (typically exceeding 60℃) and mechanical extrusion processes at this stage will completely destroy the inoculum's activity, rendering the product unsuitable as "live bacteria fertilizer." For producing organic fertilizer with high live bacteria content, inoculum can be added via spray inoculation after granulation and cooling to below 30℃, followed by immediate sealing and packaging.

In summary, the key timing for adding microbial inoculum to a bio-organic fertilizer production line is at the initial fermentation stage. Supplementary additions are recommended during the secondary fermentation period or after cooling. It is crucial to strictly avoid high-temperature pre-treatment and post-treatment stages, and to ensure suitable environmental conditions are met to maximize the decomposition and transformation effects of the inoculum, producing high-quality and efficient bio-organic fertilizer.