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CIRCULAR 2 51, U. S. DEPARTMENT OF AGRICULTURE 



A few commercial growers have experimented along this line for 

 several years, and the problem was undertaken by the United States 

 Department of Agriculture and the Pennsylvania Agricultural 

 Experiment Station in 1928. The experiments made in the depart- 

 ment have shown that the English process must be modified in order 

 to obtain a fermentation similar to that in mushroom compost. The 

 physical condition of the heap must be made similar to that of 

 composted stable manure, the heap must be wetted and aerated in 

 the same manner as mushroom compost, and the nitrogenous ferti- 

 lizers must be supplemented with other nutrients. The cost of artifi- 

 cial compost made with straw depends largely upon the cost of straw, 

 but since enough artificial compost can be made from a ton of dry 

 straw to fill as much bed space as 3 to 5 tons of stable-manure 



Figure 9. — Floor beds in a cave, St. Paul, Minn. 



compost will fill, the cost of the finished artificial compost, in most 

 localities, should be about the same as that of stable-manure compost, 

 or less. A straw compost, properly handled, will yield a crop of 

 more than 1 pound of mushrooms per square foot when used alone 

 or mixed with stable-manure compost. (Fig. 10.) However, the 

 average yields from artificial manure in the experiments of the 

 department at the Arlington Experiment Farm in Virginia have 

 been lower and more inconsistent than yields from composted horse 

 manure. The reasons for these inconsistencies are not thoroughly 

 understood. Therefore, although the experiments appear promising, 

 the department does not advise the use of artificial manure for com- 

 mercial mushroom growing until more experiments have been made. 

 In experimenting with artificial manure on a small scale the fol- 

 lowing recommendations should be observed: 



