Fermentation Maturity Judgment Index

1, Ripening Degree: the Degree of Fermentation Ripening
1) Appearance change: the intuitive qualitative judgment standard is that the fermentation is no longer intense decomposition, the finished product temperature is low; the appearance is tea-brown or black; the structure is loose; there is no bad odor.
2) Temperature change: usually the temperature of the fertilizer pile will gradually drop after the high temperature stage. When the fermentation reaches maturity, the pile temperature will be lower than 40℃.

2, Chemical Indicators
1) Changes in organic matter and volatile solids content: As fermentation proceeds, the fermented organic matter and volatile solids content show a continuous downward trend and finally reach basic stability. When it reaches maturity, it can drop 15-30%. However, this trend is greatly influenced by the source of the raw material. It is not sufficient to use it only to measure whether the fermentation is rotten or not.
2) Changes in nitrogen, C/N ratio and inorganic nitrogen form: During the fermentation process part of the organic carbon will be oxidized to CO2 and volatilized and lost, and the mass of the fertilizer pile will be reduced. Since the loss of nitrogen (mainly in the ammonification stage of organic nitrogen, a small amount of ammonia nitrogen will be volatilized and lost) is much lower than the loss of organic carbon, therefore, after fermentation and decay, the whole nitrogen content in fermentation has a tendency to rise, while the C/N ratio continues to decline until it is stable. Some studies point out that the fertilizer pile will reach stability when the C/N ratio of the pile decreases from 25 to 35:1 to less than 20:1.

Water-soluble organic carbon (C) and the 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 decay, the value of about 5-6 indicates that the fermentation has been decayed, and the value is independent of the fermentation raw materials.