Detailed Explanation of the Biological Characteristics and High-Yield Cultivation Techniques of Agaricus bitorguis

Agaricus bitorguis (Quel.) Sacc., also known as the double-ringed mushroom or the large fleshy mushroom, is a high-temperature grass-inhabiting fungus that grows on grassland. In recent years it has been domesticated and introduced. Compared with the button mushroom (Agaricus bisporus), it has broader adaptability and stronger stress resistance, and is suitable for extensive cultivation. It is relatively tolerant of heat, drought, water and carbon dioxide, does not produce a mycelial mat, does not exude yellow liquid, and comes to market 1 month earlier than the button mushroom, giving it an advantage in production season. It has been reported that abroad each ton of compost can produce 410-650 kg of fresh mushrooms, while in China each ton of compost produces 310-350 kg of fresh mushrooms.

1 Morphological characteristics

The cap of Agaricus bitorguis is 6-20 cm in diameter, initially hemispherical, later flattened hemispherical, with a flat or slightly depressed top, white, later turning dull yellow, without scales; the flesh is white, thick and firm, turning slightly pale red where injured, with slower discoloration when young; the gills are white, later turning pink to dark brown, crowded, narrow, free, of unequal length; the stipe is short, solid, nearly cylindrical; the annulus is double-layered, white, membranous, located at the middle of the stipe. Spores are dark brown, broadly elliptical to nearly spherical, smooth.

2 Growing conditions

2.1 Nutrition. Agaricus bitorguis uses cellulose, hemicellulose and lignin in compost such as wheat straw, rice straw and sawdust as its main carbon sources, and uses proteins and amino acids in supplements such as wheat bran or rice bran as nitrogen sources; it also utilizes the mineral elements and vitamins contained in the compost.

2.2 Temperature. Agaricus bitorguis is a high-temperature fungus; the optimum temperature for mycelial growth is 25-30°C, and the fruiting bodies still have a relatively high fruiting rate at 23-25°C.

2.3 Moisture. The suitable water content of the compost is 65%. In bed cultivation water evaporates quickly, so the relative air humidity should be kept at 65%-75%. During primordium differentiation and fruiting body growth, it should be kept at 85%-95%.

2.4 Air. In the early stage of mycelial growth, the oxygen requirement is not high. As the mycelium grows, ventilation should be strengthened to keep the mushroom house air fresh. During primordium formation and fruiting body growth, metabolism is vigorous, so ventilation and air exchange should be strengthened to ensure an adequate oxygen supply and to remove the carbon dioxide produced during growth.

2.5 Light. The mycelial growth stage does not require light; shading should be used during cultivation. Primordium differentiation and fruiting body growth require 100-500 Lx of diffused light.

2.6 pH. A slightly acidic compost is favorable for the growth of Agaricus bitorguis, with an optimum pH of 5.5-6. The casing soil pH should also be on the acidic side, with 5.7-6 being most suitable.

3 Cultivation techniques

Agaricus bitorguis can be cultivated on shelves with unfermented compost or in beds with fermented compost. The specific methods are described below.

3.1 Production season. The mother culture is generally made from late January to late February, the stock culture is made in early March, and the spawn for cultivation is made from early May to early June. According to the climatic conditions of the North China region, composting is scheduled for early to mid-July, spawning in mid-July, and casing in mid-August. The first batch of mushrooms can be harvested on September 10, the second batch around September 20, and the third batch in early October. After October 10, because of falling temperatures, fruiting decreases markedly; under natural temperatures, generally 3 batches of mushrooms are harvested.

3.2 Unfermented compost bed cultivation. Use 95% sun-dried cottonseed hulls, add 2% gypsum powder, 0.1% chlorothalonil and 2% calcium carbonate, and mix thoroughly; dissolve 2% sugar and 0.1% potassium dihydrogen phosphate in water beforehand and mix into the compost. The compost water content is 65% and the pH is 7.5. Spread the compost onto the bed and spawn in layers: spread a first layer of compost 5-7 cm deep and broadcast the spawn; spread a second layer of compost 5-6 cm deep, broadcast a layer of spawn, then spread another thin layer of compost over the surface to cover the spawn. The total thickness of the compost is 15-20 cm. Level and firm it, cover with newspaper and plastic film, and maintain the moisture in the compost. After spawning, incubate the mycelium at 18-28°C. When the mycelium has colonized 2/3 of the compost or has completely run through it, cover with 2-3 cm of weathered coal the size of broad beans, and after 7-10 days cover with 2-3 cm of fine soil. Then carry out routine management: ventilation, watering and increasing the indoor air humidity.

3.3 Fermented compost bed cultivation. Using 40% fresh wheat straw, 57% cattle and sheep manure, 1% gypsum powder, 1% superphosphate and 1% urea, prepare fermented compost according to the composting method for the button mushroom, turning the pile 5 times, and load the compost while it is hot. Then remove lumps of manure and debris from the compost and spread it on the surface of the greenhouse ground bed, with a compost thickness of 20 cm. When the compost temperature drops below 30°C, spot-spawn pieces of spawn the size of walnuts in layers. After spawning, cover the compost surface with plastic film to incubate the mycelium, and apply casing soil when the mycelium has run through the compost.

In the above two cultivation methods, 2-3 days after inoculation the mycelium begins to resume growth, and the new mycelium spreads outward through the compost until it has run through the compost. During the incubation period some hyphae develop, thicken and form rhizomorphs; after covering with weathered coal granules, the mycelium climbs up along the soil and compost, interweaves and knots with one another, and gradually produces fruiting bodies.

3.4 Fruiting management. About 15 days after casing, mushroom buds begin to appear. Several days before fruiting, ventilation should be reduced, and watering should be sufficient and more frequent. When fruiting bodies appear, apply 1 heavy watering, and keep the indoor relative humidity at 75%-85%. The first flush of Agaricus bitorguis fruits relatively late; the first flush can be harvested only about 22 days after casing, and the interval between two flushes is 12-15 days. The autumn harvest period of the button mushroom is about 45 days, whereas that of Agaricus bitorguis is shorter, with an effective fruiting time of only about 30 days. The yield of the first 2 flushes is similar to that of the creeping-type strains of the button mushroom. The time from mushroom bud formation to veil opening in Agaricus bitorguis is quite short, so timely harvesting is very important. Agaricus bitorguis should be picked while young and tender, with a cap diameter of 2.5-3 cm at harvest. If picking is too late, the fresh mushrooms tend to open their veils after harvest, and after the veil opens the gills quickly turn black, the commercial quality declines, which is not conducive to @#@136@#@.