Detailed Explanation of Agaricus bisporus Cultivation Technology in Rice Fields
Cultivating Agaricus bisporus in rice fields is a "rice-mushroom-rice" cropping model in which, after the rice harvest, compost is spread directly on the rice field for spawning and casing soil cultivation to produce mushrooms. After the rice is harvested, the rice straw is dried on site, composted and fermented on site to make the growing substrate, and cultivated on site, with management provided by grass curtains, small plastic tunnel shelters, or plastic greenhouses, eliminating the need to build mushroom houses and transport raw materials, thus greatly reducing production costs. In addition, rotating the cultivated field each year can effectively control pests and diseases, enabling the mushroom products to meet pollution-free quality requirements. Furthermore, cultivating Agaricus bisporus in rice fields is a good method for effectively and comprehensively utilizing crop straw; the straw residue left after mushroom cultivation is returned to the field on site, and when rice is planted again, less fertilizer can be applied, laying the foundation for producing high-quality pollution-free rice. According to practical experience in cultivating Agaricus bisporus, each mu can produce 4000-5000 jin of fresh mushrooms, with an annual output value of about 7000 yuan; after deducting production costs, the net income per mu can reach more than 3000 yuan.
I. Biological Characteristics of Agaricus bisporus
(I) Life History
The mycelium of Agaricus bisporus develops into fruiting bodies; after the fruiting bodies open, they produce spores, namely seeds, and the seeds then develop into mycelium. This is one growth cycle of the mushroom, but it can also reproduce by mycelium, which is the propagation method commonly used in cultivation.
(II) Nutritional and Physiological Characteristics
Agaricus bisporus is a straw-rotting fungus. Its best carbon sources are the decomposition products of cellulose and hemicellulose; suitable nitrogen sources are urea, ammonium salts, and various amino acids. During the composting and fermentation process, nitrogen in the compost is used by microorganisms and converted into microbial cell protein, and these microbial cell proteins are decomposed into high-quality nitrogen sources for the growth of Agaricus bisporus. Agaricus bisporus cannot directly utilize straw raw materials; they must first be composted, fermented, and decomposed, that is, degraded by microorganisms, before they can be used. Therefore, cultivating Agaricus bisporus cannot directly use straw, which differs from the production methods of edible fungi such as oyster mushrooms, shiitake mushrooms, and wood ear mushrooms.
In addition, mineral elements are also indispensable for the growth of Agaricus bisporus. The required mineral elements are mainly calcium, magnesium, potassium, phosphorus, sulfur, and so on. Therefore, in production, gypsum, calcium carbonate, superphosphate, and lime are often added to the compost to supplement mineral elements.
(III) Ecological Conditions
1. Temperature: The temperature range for the mycelial growth of Agaricus bisporus is 5°C-33°C, with the optimum growth temperature being 22°C-26°C. Below 5°C, mycelial growth is extremely slow; above 33°C, mycelial growth basically stops; above 40°C, it will die. The temperature range for the growth and development of fruiting bodies is 4°C-24°C, with the optimum growth temperature being 14°C-18°C. When the temperature is above 19°C, the fruiting bodies grow quickly, the stipes are long, the flesh is loose, the caps open easily, and the quality is poor. When the temperature is below 12°C, the fruiting bodies grow slowly and few mushrooms emerge, but the mushrooms are large, thick, and firm in texture. The spore germination temperature is about 24°C.
2. Water and Humidity: The water for the mycelial growth of Agaricus bisporus mainly comes from the compost, the casing soil layer, and water vapor in the air. During the mycelial growth stage, the suitable moisture content of the compost is about 60%. When the moisture content is above 70%, oxygen in the compost is insufficient, linear mycelium often appears, vitality declines, and the spread of mycelium in the compost layer is affected; if the moisture content is below 50%, the mycelium grows slowly, there is much fluffy mycelium and it is fine and weak, and fruiting bodies are not easily formed. During mycelial growth, the moisture content of the casing soil layer should preferably be 20%-22%, and the relative air humidity should be maintained at about 75%. If the moisture content of the casing soil layer is too high, it will affect the growth of mycelium into the lower layer of the compost, and instead a large amount will appear in the casing soil layer, which will affect yield and quality.
During the growth of fruiting bodies, the relative air humidity in the environment is required to reach about 90%. If the humidity is below 80%, scales will appear on the surface of the fruiting bodies, thereby reducing quality; if it remains in a high-humidity state above 95% for a long time, primordia and young mushrooms are likely to die. The water needed by the fruiting bodies is mainly satisfied through the moisture content of the casing soil layer.
3. Air: Agaricus bisporus is an aerobic fungus. During the growth of both mycelium and fruiting bodies, it continuously takes in oxygen and releases carbon dioxide. Therefore, the compost, casing soil layer, and environment are required to be ventilated and air-permeable. If the permeability of the compost and casing soil layer is poor, insufficient oxygen will inhibit the growth of mycelium into the compost layer. During the occurrence of fruiting bodies, if oxygen is insufficient and the carbon dioxide concentration is too high, it will affect the occurrence of fruiting bodies and promote elongation of the stipes of the fruiting bodies.
4. Light: Neither the mycelial growth nor the fruiting body development of Agaricus bisporus requires light. Strong light inhibits mycelial growth; during the growth of fruiting bodies, if they are in a lighted environment, the surface of the mushrooms will turn red, thereby reducing commercial quality. Therefore, the entire growth stage of Agaricus bisporus needs to be carried out in a dark environment.
5. pH: The pH range for the mycelial growth of Agaricus bisporus is 5.5-8.5, and the optimum pH is about 7, that is, a neutral environment. Because the mycelium of Agaricus bisporus produces organic acids during growth, thereby lowering the pH of the compost, before spawning the pH should be appropriately raised so that the pH reaches about 7.5, and the pH of the casing soil layer reaches 7.5-8.
6. Other Factors: The mycelium of Agaricus bisporus needs to contact soil before mushrooms can grow, that is, casing soil is needed during cultivation; metabolites of Pseudomonas putida in the soil induce the formation of fruiting bodies.