1.Maturity of fermentation:

Appearance change: the visual qualitative judgment standard is that the fermentation will not undergo fierce decomposition, the product temperature is lower, the appearance is tea brown or black, and the structure is loose without odor;

Temperature change: after the high temperature stage, the temperature of the compost will gradually decrease. When the fermentation reaches maturity, the temperature of the fertilizer is basically consistent with the normal temperature.

2.Chemical index:

Changes of organic matter and volatile solid content: with the progress of fermentation, the content of organic matter and volatile solid showed a continuous downward trend, and finally reached the basic stability. When it reaches maturity, it can decrease by 15-30%. However, this trend is greatly affected by the source of raw materials. It is not enough to judge whether the fermentation is rotten or not.

The change of C / N ratio and inorganic nitrogen forms: during the fermentation process, part of organic carbon will be oxidized to carbon dioxide, volatilization loss, and the mass of compost pile will be reduced. Some studies have shown that when the C / N ratio of compost decreases from 25-35:1 to below 20:1, the compost will be stable.

Ratio of water-soluble organic carbon to organic nitrogen: the ratio of water-soluble organic carbon to water-soluble organic nitrogen is a good chemical indicator of fermentation maturity. When the value is about 5-6, it indicates that the fermentation has been decomposed, and this value has nothing to do with the fermentation raw materials.