How should the turning frequency be controlled during organic fertilizer fermentation?

Turning the compost pile is the core process of aerobic fermentation and a critical step in organic fertilizer production; it directly determines oxygen supply, temperature rise, and the uniformity of decomposition, making it a key operation for ensuring product quality and preventing fermentation failure. Excessive turning dissipates heat and slows the fermentation process, while insufficient turning leads to oxygen deprivation (anaerobic conditions), unpleasant odors, and uneven decomposition. Therefore, the frequency must be precisely regulated based on the fermentation stage, pile temperature, and material condition.

The complete fermentation process comprises three stages: the heating-up phase, the high-temperature phase, and the cooling/maturation phase. Turning frequencies differ significantly across these stages, requiring stage-specific, refined management. The heating-up phase covers the initial 1 to 4 days, during which microorganisms multiply rapidly and the pile temperature rises; frequent turning is unnecessary at this time. Disturbance should be minimized to allow stable microbial proliferation, with only light turning performed if the pile lacks oxygen or heats up too slowly, thereby ensuring basic oxygen supply and laying the groundwork for the subsequent high-temperature phase.
The high-temperature phase is the core of fermentation and the critical period for managing turning operations, typically lasting 5 to 15 days. During this stage, the pile temperature stabilizes between 55°C and 70°C, making it the crucial time for eliminating insect eggs, weed seeds, and harmful bacteria, and for rendering the material harmless. Specialized organic fertilizer compost turning machines are typically used, with turning performed every 2 to 5 days to ensure sufficient oxygen levels. Turning involves moving cold, wet material from the bottom to the middle and surface material to the interior; this ensures uniform heating and allows excess moisture to escape, preventing water accumulation and anaerobic rotting within the pile.
During the cooling and maturation phase, the pile temperature gradually drops, microbial activity subsides, and material decomposition stabilizes, allowing for a gradual reduction in turning frequency. Turning is performed every 7 to 10 days during the mid-to-late fermentation stages, and the interval can be extended to every 10 to 15 days once the process enters the final aging stage. Turning operations can cease once the pile temperature approaches ambient levels without rebounding, and the material appears loose, odorless, uniform in color, and fine in texture—indicating that the material has largely matured.
Parameters must be adjusted flexibly during actual organic fertilizer production: in overcast, rainy, or high-humidity weather, turning frequency should be increased to accelerate moisture evaporation and prevent mold growth; conversely, in hot, dry weather, turning frequency should be reduced to minimize the excessive loss of heat and moisture. Scientifically managing the turning frequency not only effectively shortens the fermentation cycle but also enhances the organic matter content and stability of the finished product, thereby ensuring higher quality and greater efficiency in production.