THE BEDS.—The most common type of beds is known as the "flat bed." It is made on the floor or on shelves as shown in the illustrations. It is usually about 10 inches deep. Another type, principally used in France, is known as the "ridge bed," and requires more labor than the flat bed. The mushroom house and shelves, if used, should be frequently disinfected and whitewashed in order to avoid danger from insects and bacteria. The preparation of the beds and subsequent operations will be shown in connection with the other subjects.
PREPARATION OF THE MANURE.—The best manure is obtained from horses fed with an abundance of dry and nitrogenous food. The manure of animals fed on greens is undesirable. Growers do not all follow the same method of fermenting or composting the manure. When first unloaded, the manure is left in its original state for a few days. It is then piled in heaps about three feet deep and well pressed down. In this operation the material should be carefully forked and well mixed, and wherever found too dry, it should be lightly sprinkled. It is allowed to remain in that condition for about six days when it is again well forked and turned. In the latter operation it receives an additional light sprinkling; the dry portions are turned inside in order that the whole mass may be homogenous and uniformly moist, and the heap is again raised to about three feet. About six days later the operation is repeated, and in about three days the manure should be ready for the beds. It is then of a dark brown color mixed with white, free from objectionable odor. It is unctuous, elastic and moist, though not wet, and should not leave any moisture in the hand.
Of course, the above rules are subject to modification according to the condition of the manure, its age and previous handling.
SPAWNING.—The manure, having been properly composted, is spread evenly on the floor or shelves and firmly compressed in beds about ten inches in depth. The temperature of the bed is then too high for spawning and will usually rise still higher. It should be carefully watched with the aid of a special or mushroom thermometer. When the temperature of the beds has fallen to about 75° or 80°, they may be spawned. The beds must be spawned when the temperature falls, never when it rises. The bricks of spawn are broken into eight or ten pieces, and these pieces are inserted from one to two inches below the surface, about nine to twelve inches apart. The bed is then firmly compressed. An advantage is found in breaking and distributing the spawn over the surface of the bed a few days before spawning; this allows the mycelium to absorb some moisture and swell to some extent. If the bed is in proper condition it should not require watering for several weeks.
Figure 501.—Brick Spawn, Pure Culture.
CASING THE BEDS.—As soon as the spawn is observed to "run," or from eight days to two weeks, the beds are "cased" or covered with a layer of about one inch of light garden loam, well screened. The loam should be slightly moist, and free from organic matter. The beds should now be watched and should not be allowed to evaporate or dry out.
PICKING.—Mushrooms should appear in from five to ten weeks after spawning, and the period of production of a good bed ranges from two to four months. In picking the mushrooms an intelligent hand will carefully twist it from the soil and fill the hole left in the bed with fresh soil. Pieces of roots or stems should never be allowed to remain in the beds, otherwise decay might set in and infect the surrounding plants. A good mushroom bed will yield a crop of from one-half to two pounds per square foot. Mushrooms should be picked every day or every other day; they should not be left after the veils begin to break.