The fermentation process of organic fertilizers mainly includes the following steps:
Raw Material Selection and Pretreatment:
Raw Material Selection: Common raw materials for organic fertilizers include livestock and poultry manure (such as chicken manure, cow manure, pig manure, etc.), crop straws, fallen leaves, weeds, food processing waste, etc. These raw materials need to be ensured to be free from harmful substances and heavy metal pollution and have a reliable source.
Raw Material Crushing: Crush the raw materials with large volume and hard texture. For example, straws and branches can be crushed into small sections or powder form using a crusher. This can increase the surface area of the raw materials, which is beneficial for the decomposition and fermentation by microorganisms and also convenient for subsequent mixing operations.
Moisture Adjustment: Test the moisture content of the raw materials and generally adjust it to about 55% – 65%. If the moisture is too high, some dry materials such as straw powder or rice husk powder can be added for absorption; if the moisture is too low, an appropriate amount of water needs to be added.
Carbon-Nitrogen Ratio Adjustment: An appropriate carbon-nitrogen ratio (C/N) is very important for the fermentation of organic fertilizers. Generally, a suitable carbon-nitrogen ratio is between 25:1 and 30:1. If the carbon-nitrogen ratio of the raw materials is not appropriate, for example, the nitrogen content of livestock and poultry manure is relatively high, some substances with high carbon content such as straws and sawdust can be added for adjustment.
Inoculum Addition and Mixing:
Inoculum Selection: According to different raw materials and fermentation requirements, select appropriate microbial fermentation inocula. Common ones include Bacillus subtilis, lactic acid bacteria, yeast, etc. These inocula can accelerate the decomposition and transformation of organic substances, improving the fermentation efficiency and the quality of organic fertilizers.
Inoculum Addition: According to the instructions of the inoculum, evenly add the fermentation inoculum to the pretreated raw materials. You can first premix the inoculum with a small amount of raw materials and then thoroughly stir and mix it with a large amount of raw materials to ensure that the inoculum can be evenly distributed.
Composting Fermentation:
Pile Building: Stack the mixed raw materials into piles of a certain shape and size. Generally, the pile height is 1.5 – 2 meters, the width is 2 – 3 meters, and the length depends on the actual situation. The shape of the pile can be trapezoidal, triangular or rectangular, etc., so as to maintain the stability and good ventilation of the pile body.
Turning the Pile: During the fermentation process, regular pile turning operations are required. Usually, the pile is turned once every 2 – 3 days. The purpose of turning the pile is to provide oxygen, so that the materials inside the pile can fully contact the air, promoting the aerobic fermentation of microorganisms; at the same time, it can also adjust the temperature and humidity of the pile body, avoiding local overheating or overwetting.
Temperature and Humidity Control: During the fermentation process, the temperature of the pile body will gradually increase. Generally, in the initial stage of fermentation, it will go through a mesothermal stage (from room temperature to about 50°C), then enter a high-temperature stage (above 50°C, up to about 70°C), and finally the temperature will gradually decrease and enter the decomposition stage. It is necessary to closely monitor the temperature changes of the pile body. When the temperature is too high, the number of pile turnings can be appropriately increased or the pile height can be reduced to prevent the high temperature from inhibiting the activity of microorganisms; when the temperature is too low, measures such as covering with thermal insulation materials can be taken to raise the temperature of the pile body. In addition, it is also necessary to keep the appropriate humidity of the pile body, avoiding being too dry or too wet.
Fermentation and Decomposition:
Fermentation Time: The whole fermentation process needs to last for a certain period of time, generally about 15 – 30 days. The specific time depends on factors such as the type of raw materials, fermentation conditions and fermentation inocula. When the temperature of the pile body gradually decreases and stabilizes below 40°C, and the color of the materials turns black, the texture is loose and there is no bad smell, it indicates that the fermentation has basically decomposed.
Post-ripening Treatment: The materials after fermentation and decomposition still need to undergo a period of post-ripening treatment to further improve the quality and stability of the organic fertilizers. The post-ripening treatment time is generally about 7 – 10 days. During this period, pile turning or natural ventilat