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Mushrooms are a popular edible fungus, and their growth depends on high-quality compost. Mushroom compost not only provides nutrients for mushroom mycelium, but also creates a suitable physical and chemical environment for its growth. Making high-quality mushroom compost is one of the key steps for successful mushroom cultivation. This article will give a detailed introduction to the process, principles and related points of mushroom compost making.
what is spent mushroom compost？
Mushroom compost is an organic fertilizer specially made for growing mushrooms. It is formed by piling and fermenting various organic raw materials. Mushroom compost provides comprehensive nutrition for mushroom growth. It is rich in carbon and nitrogen sources, minerals and other nutrients,
Mushroom compost
Principle of mushroom composting
Mushroom composting is a complex microbial fermentation process. In this process, various microorganisms (bacteria, actinomycetes, fungi, etc.) decompose the organic matter in the raw materials under suitable conditions. These microorganisms use nutrients such as carbon and nitrogen sources in the raw materials for growth and reproduction, while releasing heat, carbon dioxide and metabolic products.
The role of microorganisms in mushroom composting
Bacteria
Bacteria are the main decomposers in the early stages of composting. They are numerous and reproduce quickly. For example, some mesophilic bacteria can quickly decompose easily degradable organic matter in the raw materials, such as simple sugars and proteins, at the beginning of composting, creating conditions for the compost to heat up. As the temperature of the compost increases, thermophilic bacteria become active. They can decompose more complex organic matter, further promoting the composting process.
Actinomycetes
Actinomycetes play an important role in the high-temperature stage of composting. They can decompose complex macromolecular organic matter such as lignin and cellulose, and help improve the physical structure of the compost, making it more loose and porous. At the same time, the metabolites of actinomycetes also have a certain effect on inhibiting pathogenic bacteria.
Fungi
Fungi are positive for the formation of stable humus in the later stages of composting. They can decompose some organic matter that is difficult to be decomposed by bacteria and actinomycetes, and the mycelium can wrap around the compost material, enhance the agglomeration of the compost, and improve the water and fertilizer retention capacity of the compost.
Physical and chemical changes during mushroom composting
Temperature change
Once composting has started, the activity of the microorganisms gradually raises the temperature. Generally, within 2-3 days after the composting process begins, the temperature can rise from the ambient temperature to 40-50°C, which is the mesophilic stage. With the proliferation of
Carbon-nitrogen ratio change
The initial carbon-to-nitrogen ratio of raw materials is usually high. During the composting process, microorganisms decompose organic matter to consume carbon sources, while fixing some of the nitrogen in the microorganisms, resulting in a gradual decrease in the carbon-to-nitrogen ratio. A suitable carbon-to-nitrogen ratio is essential for the growth of mushroom mycelium. The carbon-to-nitrogen ratio of mature compost is generally around 17–20:1.
PH change
During the initial stage of composting, the pH value may decrease due to the production of organic acids by microorganisms decomposing organic matter. As composting progresses, the pH value will increase due to the release of alkaline substances (such as ammonia) and the addition of regulating substances (such as lime). The pH value needs to be adjusted appropriately during the composting process, as the pH value range suitable for mushroom growth is generally around 7–7.5.
Physical and chemical changes during mushroom composting
Mushroom compost material
Main source of materials
Wheat straw
Wheat straw is one of the high-quality main ingredients for mushroom compost. Its advantage is that it is relatively soft and can be easily broken down by microorganisms. Before use, the wheat straw needs to be chopped, usually into 3–5 cm pieces. This length increases the contact area between the straw and air and microorganisms, which is beneficial for speeding up the decomposition process. At the same time, wheat straw contains the right amount of cellulose, hemicellulose and lignin, providing a rich carbon source for microbial growth.
Corn stalks
Corn stalks are also a commonly used ingredient. They have a high cellulose content but are relatively hard. They should also be chopped up before use, and because they are relatively difficult to decompose, they may require more careful management during the composting process, such as increasing the number of compost turns or extending the composting time. However, the rich nutrients in corn stalks can provide long-lasting nutrient support for mushroom growth.
Rice straw
Rice straw is widely available and is characterized by its fine fibers, which decompose quickly. When selecting rice straw, try to choose fresh, mold-free straw. The decomposition of rice straw in the compost can provide a rapid release of heat at the beginning of the composting process, promoting the reproduction of microorganisms.
Horse manure
Horse manure is a manure with good air permeability and rapid heat production. It is loose in texture and contains a large amount of microorganisms and incompletely digested organic matter. Horse manure has a moderate fiber content, which is conducive to the formation of a good aerated structure in composting. During composting, horse manure can quickly start the fermentation process, causing the temperature of the compost to rise rapidly. However, horse manure releases nutrients relatively quickly and needs to be used in conjunction with other long-lasting fertilizer sources.
Cow dung
Cow dung is relatively fine in texture, rich in nutrients and has a long-lasting effect. It contains a large amount of organic matter, nitrogen, phosphorus, potassium and other nutrients, and is a high-quality nitrogen source and source of organic matter in mushroom compost. Fresh cow dung contains a high amount of water, so it can be dried in the sun or mixed with other drier ingredients before use to adjust the moisture content of the compost.
Chicken manure
Chicken manure is a highly effective fertilizer, as it is high in nitrogen, phosphorus and potassium. However, it also contains relatively high levels of salt, so care must be taken when using it to avoid any adverse effects on mushroom growth. In general, the amount of chicken manure used in mushroom compost should not exceed 10% – 15% of the total amount of raw materials. Chicken manure should also be fully composted before use to reduce the production of harmful gases such as ammonia and the spread of pathogenic bacteria.
Source of auxiliary materials
Urea
Urea is a common nitrogen fertilizer with a high nitrogen content (about 46%). Adding urea to the compost can adjust the carbon-nitrogen ratio, provide microorganisms with an adequate nitrogen source, and promote their growth and reproduction. The amount added is generally determined based on the carbon-nitrogen ratio of the raw materials and the size of the compost, usually 0.5% – 1% of the dry weight of the raw materials. Urea will gradually decompose during the composting process, releasing ammonia gas. Therefore, it is important to mix it thoroughly with other raw materials to avoid high local concentrations of ammonia.
Ammonium sulphate
Ammonium sulphate is also an effective nitrogen fertilizer. In addition to providing nitrogen, it also adds a certain amount of sulphur to the compost. The acidity of ammonium sulphate can be used to a certain extent to adjust the pH of the compost, which is especially suitable for some raw material combinations with high alkalinity. The amount used is generally similar to that of urea, accounting for 0.5% – 1% of the dry weight of the raw materials.
Gypsum
Gypsum has multiple functions in mushroom compost. It improves the physical structure of the compost, making it more porous and preventing it from becoming compacted later on, which is beneficial for air circulation and water penetration. Gypsum also regulates the pH of the compost, buffering against changes in pH during the composting process. In addition, gypsum binds some harmful substances in the compost (such as excess ammonium ions), reducing the negative impact on mushroom growth. The usual amount of gypsum added is 1% – 2% of the dry weight of the raw materials.
Superphosphate
Superphosphate is an important source of phosphorus for mushroom growth. Phosphorus is essential for the growth of mushroom mycelium and the formation of fruiting bodies, for example, by participating in cell division and energy metabolism. Adding superphosphate to the compost promotes the spread of mushroom mycelium in the compost and improves the yield and quality of the mushrooms. The amount of superphosphate added is about 0.5% – 1% of the dry weight of the raw materials.
Mushroom composting process
Mixing of ingredients
Mix the main ingredients and auxiliary ingredients thoroughly according to the predetermined recipe. For example, for composting double-spawn mushrooms, a common recipe is a ratio of 6:4 or 7:3 straw (such as wheat straw or corn stalks) to manure (such as horse manure or cow dung), with the addition of appropriate amounts of auxiliary ingredients such as urea, gypsum and superphosphate. The ingredients can be mixed using a loader, mixer or manually with a shovel to ensure that they are evenly mixed and to avoid localised areas with too much or too little nutrients.
Raw materials stacked in a trapezoid pile
Pile the mixed raw materials into a trapezoidal heap. The base of the heap is about 2–3 meters wide, the top is about 1–1.5 meters wide, the height is about 1.5–2 meters, and the length depends on the amount of raw materials, generally not exceeding 10–15 meters. The trapezoidal shape of the heap is conducive to the stability of the compost and prevents it from collapsing. During the composting process, some ventilation holes can be placed in the middle of the bottom of the pile, such as those made of thick branches, bamboo tubes and other materials, to enhance the ventilation effect at the bottom of the compost pile.
Timing and frequency of turning the compost
During the composting process, microorganisms decompose organic matter and produce heat. When the internal temperature of the compost reaches 65–75°C, the first turning should be carried out. This temperature range is the optimal temperature range for thermophilic microorganisms to be active. Turning the pile can turn the outer material to the inside, so that the material is evenly heated, while at the same time providing more oxygen for the microorganisms to promote further decomposition of organic matter. After the first turning, depending on the temperature changes, the pile should be turned every 4-7 days. The entire composting process generally requires 3-5 turns.
Turn over compost
The compost can be turned using a loader, a turning machine or manually. During the turning process, the compost should be thoroughly turned so that the materials originally inside the compost are fully exposed to the air, while the original outer materials are turned inside. At the same time, pay attention to the moisture of the compost. If the compost is too dry, you can spray it with water in moderation. Generally, the water should be sprayed evenly to avoid local over-moistening. If the compost is too wet, you can add some dry straw or other dry materials to adjust it. In addition, the quality of the compost can be checked during the turning process, such as whether there are undecomposed large pieces of material, whether there is an unusual smell, etc., and adjustments can be made accordingly.
Mushroom composting process
Compost quality testing and adjustment
Physical index testing
Color and texture:The mature mushroom compost should be dark brown to blackish brown in color and have a loose, granular or fibrous structure. If the compost is light in color, it may indicate incomplete decomposition of the organic matter; if the texture is too compact, it may affect the growth of the mushroom mycelium and air circulation.
Humidity: If you squeeze the compost with your hands, and water drips out but does not form a stream, the humidity is suitable. If hardly any water drips out, the compost is too dry. If there is a lot of water dripping out, the compost is too wet. Suitable humidity is crucial for the growth and spread of mushroom mycelium in the compost. Generally, the moisture content of the compost should be maintained at around 60% – 65%.
Chemical index testing
Carbon-nitrogen ratio determination: The carbon-nitrogen ratio of the compost can be tested by laboratory analysis or using some simple carbon-nitrogen ratio determination tools. The carbon-nitrogen ratio of mature compost is generally around 17-20:1. If the carbon-nitrogen ratio is too high, it indicates that the organic matter in the compost has not completely decomposed, and the composting process may need to continue or the formula may need to be adjusted. If the carbon-nitrogen ratio is too low, it may lead to the release of harmful gases such as ammonia during the use of the compost, which will affect the growth of mushrooms.
pH measurement: Use pH test strips or a pH meter to measure the pH of the compost. The pH range suitable for mushroom growth is generally around 7–7.5. If the pH is not within this range, it can be adjusted by adding substances such as lime (to increase the pH) or sulphur powder (to lower the pH).
Storage and use of mushroom compost
Storage of mushroom compost
If the prepared mushroom compost is not used immediately, it can be stored for a short period of time. The storage site should be dry and well ventilated to prevent the compost from being soaked by rain and direct sunlight. The compost can be piled into smaller piles and covered with plastic film (but be careful to maintain a certain degree of air permeability) to prevent excessive loss of moisture and mixing in of foreign matter.
Mushroom compost use
When using compost to grow mushrooms, the compost should be evenly spread on the mushroom bed. The thickness depends on the species of mushroom and the cultivation method. Generally, the thickness of the compost bed for Agaricus bisporus is about 20-30 cm. After spreading the compost, it can be disinfected by methods such as high-temperature steam disinfection or chemical disinfection to kill any remaining pathogens and pests. Then inoculate the mushroom spawn and start the mushroom cultivation process.
mushroom composting use
In short, the production of mushroom compost is a process that requires careful operation and management. From raw material selection and site preparation to compost production, quality testing and use, each link has an important impact on mushroom growth and yield. Through scientific and reasonable methods, high-quality mushroom compost can be produced to provide good substrate conditions for mushroom cultivation.
