CIRCULAR No. 509 MAY 1939 \ 



UNITED STATES DEPARTMENT OF AGRICULTURE 

 WASHINGTON, D. C. 



MUSHROOM CASING SOIL IN RELATION TO YIELD 



By Edmund B. Lambert, pathologist, Division of Mycology and Disease Survey 

 and Harry Humfeld, associate bacteriologist. Division of Soil Microbiology, 

 Bureau of Plant Industry 



Page 



Introduction 1 



E xperimental methods 2 



Thickness of casing soil 2 



Time of casing 3 



Reaction of the soil. 4 



CONTENTS 



Page 



Texture of soil 7 



Heat sterilization of soil . ]0 



Summary 10 



Literature cited li 



INTRODUCTION 



Since the beginning of mushroom culture, growers have found it 

 necessary to spread a shallow layer of soil over the beds in order to 

 induce the mycelium in the beds to produce mushrooms. This layer 

 is usually referred to as the casing soil. De Tournefort ill) 1 as early 

 as 1707 described the use of casing soil in mushroom culture in France. 

 In 1882 Lachaume (4) gave an account of casing procedure used in 

 the underground quarries of France. This procedure was essentially 

 that practiced in France today ; powdered rock was screened from the 

 debris that accumulated near the face of the stone quarries in which 

 mushrooms were grown and was mixed with soil in the proportion of 

 three parts of rock powder to one part of soil. The beds were covered 

 with this mixture to a depth of about three-fourths of an inch as soon 

 as the mycelium showed signs of running through the compost. 



According to Robinson (9) and Falconer (2), the market gardeners 

 who raised mushrooms in England and the United States prior to 1890 

 preferred a rich garden loam, which they placed on the beds, from 4 

 to 10 days after spawning, in a layer 2 to 3 inches deep. Most growers 

 pounded down the soil to a hard surface. By 1915 Duggar (1) and 

 Jackson (3) pointed out that the customary deep casing soil was giving 

 way to the thinner casing adopted by the French 30 years earlier. 

 The need for a very rich loam and firming the soil was also doubted by 

 many growers. 



At the present time growers prefer a depth of casing of from three- 

 fourths to 1% inches. They also agree rather generally that the proper 

 time to case is from 1 to 3 weeks after the mycelium has begun to 

 run in the beds. With regard to the texture of the soil, however, 

 different customs have gained favor in France, England, and the 

 United States. The French still prefer the quarry debris, le bousin, 

 which for them is probably more accessible and free from Mycogone 

 disease than the soil. Ware (12) points out that the English in order to 

 avoid Mycogone have come to use soil from at least 6 inches depth 



1 Italic numbers in parentheses refer to Literature Cited, p. 11. 

 98600°— 39 



