Procure not less than a cartload of clean, fresh stable manure. Place it under cover, to protect it from rain and drain water, mix well and heap up the whole mass into a mound three feet high then beat the mound firmly down to prevent undue heating. Repeat this operation every other day until its rank smell is gone, taking care that on each turning the outside dry manure is placed in the centre of the mound. By this means the stable odor is dissipated while its heating properties are equally distributed. Add to this from one-fourth to one-fifth of clean, rich garden mould. Mix well. After this careful handling, the mass may be considered fit for bedding purposes. When placed in the beds the mass should be compacted again by beating with the back of a spade or trowel. The bed surface should appear moist but not wet, smooth and of firm consistence. From day to day it will be necessary to test its general temperature by means of a thermometer. To this end make at various places at different depths openings sufficiently large to admit the use of a thermometer. It will be found that the temperature is highest nearest the bottom. Test at various points. At first the temperature will run high; 105° to 120° Fahrenheit is probably as high as it will reach, but in a few days it will fall to 85° or 80° Fahrenheit. At this point spawn the bed. For this purpose make holes in the top of the bed about six inches apart and two inches deep with a blunt dibble or broom handle. Place in these holes or openings a piece of brick spawn about the size of a hen's egg, and cover the holes with manure; finish by packing the same, keeping the surface of the bed smooth and moist. The spawn should be slightly moistened before using. Should the surface of the bed become dry, use water from a fine sprinkling pan. The temperature of the cellar or house in which the bed may be placed should range between 55° and 75°, and should not be lower than 50°. If the spawn is good and all conditions attended to, the white filaments should appear spreading through the bed within eight or ten days after spawning. When the white spawn is observed on or near the surface, cover the whole surface with from one to two inches of garden loam well pulverized. A good general rule for spawning the bed is to wait until the heat of the bed is on the decline and has fallen to at least 90° Fahrenheit. If the heat in the middle of the bed runs too high the spawn is killed. The experience of a number of growers has shown that a bed spawned at 60° to 80° and kept at 55° after the mushrooms appear gives better results than one spawned at 90°.
The quality of the manure makes some difference in its temperature. That obtained from stables where horses are grass fed will be of lower normal temperature and will chill quicker than that obtained from corn or oat fed stock.
A solution of saltpeter in proportion of about fifteen grains to a quart of water, occasionally spread over the bed with a fine hose, helps to accelerate the growth of the mushrooms.
The proper condition of the manure as regards dryness or moistness can be readily ascertained by squeezing it in the hand; it should be unctuous enough to hold together in a lump, and so dry that you cannot squeeze a drop of water out of it. Excessive moisture in the manure has been often a cause of failure. It should be remembered also that when the heat of the manure is on the decline it falls rapidly, five, often ten degrees a day, till it reaches about 75°, and between that and 65° it may rest for weeks.
One of the principal causes of the failure of mushroom culture in this country is the use of old or poor spawn. Good spawn should have a fresh, mushroomy odor, and a bluish-white appearance on the surface. In buying spawn one should always go to reliable seedsmen.
Compost for Mushroom Beds.
Sawdust has been used in England for mushroom beds, after having been used for stable bedding, with very good results. It has also been used successfully in the District of Columbia. In fact, the very large models of cultivated mushrooms exhibited by the Division of Microscopy of the Department of Agriculture at the World's Fair in Chicago were moulded from mushrooms which were grown on the writer's premises, in a composition of sawdust stable bedding, combined with about one-fourth garden mould, but I am confident, at the same time, that much depends on the kind of timber the sawdust is made from. In this case the sawdust came from spruce.
Mushroom Culture in Canada.
A Canadian correspondent informs me that he, with others, has been very successful in growing mushrooms in the open air during the summer months in Canada, and gives the following directions for preparing the beds in the colder latitudes:
Place under a shed such amount of clean stable manure as may be required for the beds, turning it over and over until all free ammonia has escaped and the tendency of undue fermentation and evolution of high temperature has greatly modified. To effect this, it is necessary to heap up the manure each time in a mound, say three feet high after turning, and beat it firmly down (the exclusion of free air prevents overheating). To put the manure in proper condition for use in the beds, from two to four weeks' treatment may be required, but much depends on the quality of the manure and temperature of the atmosphere. Before making the beds, and several days after the last turning, test the internal temperature of the mound in the following manner: Make a hole with a broomstick through the mound from top to bottom, and suspend a thermometer half way down in the hole for, say, an hour. The temperature may be as high as 150° F. After the lapse of the time stated, beat the mound more firmly down to prevent rise of temperature. Test again two days after in the same manner. If the temperature has risen several degrees the mound must be again taken down, turned over, and remade. If, on the other hand, the temperature has fallen to 100° F., the permanent bed may be made. If indoor growth is desired, such as a cellar, outbuilding, or cave, the atmosphere must not fall below 50° F., nor be over 80° F. Air drafts cannot be permitted. The floor must be dry and the atmosphere moist. The cellar may be dark, or moderately light. Growers differ in opinion in this respect. Growers generally add to the manure about one-fourth or one-fifth garden soil, but success has been attained without the use of garden soil, except as surface dressing after spawning the bed; an excessive use of loam, in any case, tends to lower the temperature too rapidly. Having prepared a box or frame-work for the bed twelve inches deep, fill it up to within two inches of the top; beat gently down with a board, or a brick, until it is even and compact. On the following day make holes in the bed, with a dibble, ten inches deep, in which suspend a thermometer half way down for an hour. Should the temperature have fallen to 90° F., cover lightly with straw and test on the following day. Should the temperature prove to be going down, say to 80° F., or 85° F., it is safe to plant the spawn; but should the temperature be on the rise, wait until it is falling. One grower has stated that his greatest success has been when the spawn was planted at the temperature of 75° F. Should the temperature fall too quickly and the surface be too dry, sprinkle with water at blood heat, using a very fine hose, and cover the bed with straw.