Volume 12 Part 1 Article 44: Recycled Casing Soil in the Culture of Agaricus bisporus

Volume 12 Part 1 Article 44
Year 1989
Title: Recycled Casing Soil in the Culture of Agaricus bisporus
Authors: I. Jablonsky and A. Srb

Abstract:

For several decades now mushroom growers have mainly been using neutralised peat moss for the casing of mushroom cultures (Edwards and Flegg 1953). This material fulfills all the requirements of mushroom culture. Peat moss absorbs water well, in combination with a suitable source of Ca it maintains the set pH value, it has a loose structure, it ensures the exchange of gases between the compost and the surrounding atmosphere and it does not form a surface crust. Recently, however, there has begun to be a shortage of peat moss in some countries and at the same time its quality has also dropped. At the present time, for instance, there has been a drop of 30 % in the production of peat moss in Czechoslovakia for reasons concerning the protection of the environment.

In this situation there are two possible ways which spring to mind for ensuring casing soil. The first is the replacement of peat moss with another alternative raw material, the second is the suitable repeated use of peat moss for casing without the yield being reduced. There have been tried as alternative materials shredded pine bark (Allen 1976), sawdust, bagasse (Nair 1985), spent mushroom compost (Wuest 1976, Jablonsky and Srb 1980), a paper mill by-product called PMBP (Yeo and Hayes 1979), Cabutz waste substrate (Levanon et al. 1986). Some of these materials, such as PMBP, proved to be of use. On the whole, however, the alternative materials tested did not have the appropriate qualities, or their quality was variable, or they were not available in sufficient quantity, or their price was exorbitant, as in the case of Hygromull (Visscher 1982).

The advantage of the repeated use casing soil is its uniform quality and savings on the cost of purchase and transport. Separated casing soil is used repeatedly in practice in Hauser Champignonkulturen AG in Gossau in Switzerland. There they let the separated casing layer lie for two years and then they mix it with peat in the ratio 7:1 (Tschierpe 1982). Nair (1983, 1985) successfully used regenerated casing soil which he washed in hot water, thus relieving it of accumulated salts and pathogenic micro-organisms. He then mixed the washed soil with fresh peat moss in the ratio 1:1. Flegg (1975), however, draws attention to a drop in yield of 11 % which occurred in his experiments with the repeated use of casing soil.

Several factors have not yet been considered in the study of the repeated use of casing soil. Firstly there has been no investigation of using soil several times over until the moment when the accumulation of materials toxic to the culture causes permanent yield depression. There has been no study of the influence of the natural accumulation of various mineral substances on the average weight of the fruit bodies, earliness and the growth of the mushroom mycelium. The separation of the casing soil from the culture during emptying in the tray system has been dealt with by the use of the Claron line, but so far the separation of the soil has not been tried for the shelf system. We therefore ascertained the influence of technical net placed between the layer of substrate and soil on the growth of the mycelium and the yield of mushroom culture.

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