Answer: Applying uncomposted organic fertilizer (such as raw manure) directly to the soil poses a serious threat to crop growth through a chain reaction of “heat generation damaging roots – pathogen spread – nutrient fixation.”

The core mechanism is as follows:

1. “Root and seedling burn” and toxic gas hazards caused by secondary fermentation: When uncomposted organic fertilizer is applied to the soil, it will initiate “secondary fermentation” under suitable temperature and humidity conditions. During fermentation, microorganisms multiply rapidly and decompose organic matter, releasing a large amount of heat. When the fermentation site is close to the crop roots or the plant is small, the heat generated will scorch the roots and inhibit growth, i.e., “root and seedling burn,” which can directly lead to plant death in severe cases. At the same time, the decomposition process also produces harmful gases such as methane and ammonia, which can cause soil and crop acidification, further damaging the root system.
2. Risk of Pathogen, Insect Egg, and Weed Seed Spread: Livestock and poultry manure often carries a large number of pathogens and pests, such as coliform bacteria and nematodes. Applying it to farmland without high-temperature composting to kill these pathogens can lead to the spread of pests and diseases and crop outbreaks. Furthermore, if weed seeds mixed in with raw manure are not killed during the composting process, they can cause weed infestations in the soil, increasing subsequent weeding costs. Full fermentation at 60℃ is necessary to effectively kill insect eggs and weed seeds.
3. Contradiction Between Nutrient Form and Crop Absorption: In uncomposted organic fertilizer, nutrients are mostly in organic or slow-release forms, which crop roots cannot directly absorb and utilize. Only after thorough microbial decomposition and transformation, mineralizing organic nutrients into readily available ammonium nitrogen, nitrate nitrogen, and soluble phosphorus and potassium, can they be effectively absorbed by crops. Direct application of raw manure not only results in slow fertilizer effects but may also compete with seedlings for soil moisture and nutrients during the early stages of decomposition.
4. [Production Recommendations] How to Ensure Fully Decomposed Organic Fermentation Through Processing?

We recommend the following decomposition assurance measures in organic fertilizer production lines:

Aerobic Fermentation Process:Utilize trough-type or disc-type compost turners for regular turning to achieve uniform aeration, promote thorough material decomposition, and ensure harmless treatment. Using trough fermentation combined with a turner effectively regulates moisture and ensures uniform mixing, achieving full decomposition.

High-Temperature Sterilization and Decomposition Standards:Through trough turning or sealed high-temperature fermentation in tanks, achieve thorough decomposition, sterilization, and egg removal, preventing root burn and bacterial contamination. Only after fermentation and decomposition can the material proceed to subsequent deep processing stages such as crushing and granulation.

Scientific Evaluation of Decomposition:We recommend using the seed germination index (GI) as a quantitative evaluation indicator of decomposition—GI > 50% indicates basic decomposition, and GI ≥ 80% indicates complete decomposition and no toxicity to plants. Industry standard NY/T 525-2021 stipulates that the GI value of commercial organic fertilizers should be ≥70%.

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