MUSHROOM GROWING IN THE UNITED STATES 11 



PREPARATION OF A SUITABLE COMPOST 

 SELECTING AND STORING MANURE 



Commercial mushroom growers use horse manure with straw bed- 

 ding almost exclusively as the raw material for mushroom compost. 

 Practical experience has led them to prefer manure from grain-fed 

 horses bedded with a moderate amount of wheat straw. Manure 

 with too much straw has a tendency to dry out and cool off because of 

 excessive evaporation. Good mushroom crops have been obtained 

 from manure with rye straw, oat straw, or even pine shavings as 

 bedding, but these materials require special treatment. Rye straw 

 is usually longer and more difficult to break up than wheat straw; 

 oat straw breaks down very rapidly and has a tendency to overheat 

 and become moldy; shavings manure makes a compact heap and 

 requires more thorough aeration than straw manure. Certain grow- 

 ers have successfully handled strawy or " long " manure from racing 

 stables by heaping it twice as high as ordinary manure at the begin- 

 ning of the composting period. In large cities, such as New York, 

 Philadelphia, and Chicago, the manure is handled by brokers who 

 contract with the stable owners and resell by the carload to truck 

 gardeners and mushroom growers. 



The manure is usually composted as soon as a rick is assembled 

 sufficient to fill the mushroom house, but at times it must be stored. 

 When storage is necessary the method most generally practiced is 

 to pile the manure into large compact heaps from 8 to 10 feet high 

 and containing at least 90 tons. The heaps are then covered with 

 several inches of soil and allowed to stand undisturbed except for 

 an occasional watering of the outside layer. Manure handled in 

 this way can be successfully stored for :£hree or four months. Ap- 

 parently the manure remains in better condition if moist, anaerobic 

 conditions are maintained inside the rick to check fermentation and 

 keep the compost " green." 



COMPOSTING THE MANURE IN THE RICK 



Composting the manure is probably the most variable operation 

 in mushroom culture. Manure assembled for different ricks, or even 

 for different parts of the same rick, is seldom exactly alike. Suc- 

 cessful growers attempt to allow for these differences by accommodat- 

 ing their composting procedure to the kind of manure. They keep 

 in mind what they consider ideal composting conditions and ideal 

 texture and appearance of the finished compost rather than a set 

 procedure for handling the manure. 



The most important factors affecting the compost that may be 

 controlled by the grower are aeration, moisture content, and tem- 

 perature. These are largely dependent on the size and shape of the 

 rick, its height, compactness, the amount of water added during 

 turning, and the number of days between turnings. The lateral 

 dimensions of the heap are usually determined by the space available 

 for composting and the amount of bed space to be filled. Ricks for 

 commercial mushroom culture usually contain 60 to 100 tons of ma- 

 nure, and are about 20 feet wide by 40 to 60 feet long. The height of 

 the rick depends somewhat on the texture of the manure. The average 



