Composting is the core step in the organic fertilizer production line. Only when raw materials are fully composted can harmful substances be eliminated, root and seedling burn be prevented, and nutrient activity be stabilized. Insufficiently fermented raw manure will undergo secondary fermentation in the soil, breeding bacteria and releasing odors, while over-composting will deplete nutrients. Therefore, accurately judging the degree of composting is crucial to ensuring fertilizer quality. In production, this can be determined through a comprehensive assessment of appearance, temperature, odor, practical operation, and physicochemical indicators.
First, visual inspection is the simplest method in organic fertilizer production. Fully composted organic fertilizer has a loose and uniform texture, without hard stalks, manure lumps, or other clumps of raw materials. It is generally dark brown or blackish-brown with a uniform color. The material is loose and not compacted, easily grasped and breathable, with no obvious impurities. Compared to the initial fermentation stage, its volume will have significantly shrunk, and its overall texture is fine. These are the basic characteristics for initially determining composting maturity.
Second, temperature and odor are the most crucial indicators of successful composting. The high-temperature fermentation stage of organic fertilizer can reach temperatures of 55 to 70℃, used for sterilization and harmlessness. When the material temperature continuously drops and stabilizes close to room temperature, without repeated temperature increases, it indicates that the fermentation reaction is basically complete. At the same time, properly fermented organic fertilizer has no pungent ammonia or fishy smell, only a faint earthy, humus-like aroma. If there is still a foul odor or sour smell, it indicates that fermentation is incomplete.
Furthermore, simple practical tests can be used to verify this. Take an appropriate amount of material, pour water on it, and let it stand; there should be no heating or bubbling. Bury the material in the soil and let it stand for several days; there should be no heating or soil burning. In addition, properly fermented organic fertilizer has a moderate moisture content; it can be formed into a clump when squeezed in the hand but crumbles easily when dropped, with a balanced dryness and wetness, meeting the basic physical standards of commercial organic fertilizer.
Large-scale production also requires precise judgment based on physicochemical indicators. Qualified properly fermented organic fertilizer has a stable organic matter content, a carbon-to-nitrogen ratio below 20:1, complete inactivation of weed seeds, insect eggs, and harmful pathogens, and a pH close to neutral. If all indicators are within acceptable limits, and considering appearance, temperature, and odor characteristics, the organic fertilizer can be determined to be fully decomposed and ready for subsequent processing steps in organic fertilizer production.
In summary, this multi-dimensional method for determining decomposition is simple, efficient, accurate, and reliable. It effectively avoids quality problems associated with raw fertilizer, ensuring that the organic fertilizer is safe, high-quality, and nutrient-rich, suitable for use in various crop cultivation.
