Volume 10 Part 2 Article 18: A New Medium for Casing Mushroom Beds

Volume 10 Part 2 Article 18
Year 1979
Title: A New Medium for Casing Mushroom Beds
Authors: S.G. Yeo and W.A. Hayes

Abstract:

The casing layer is an essential part of the total substrate in the artificial culture of Agaricus bisporus. Although many different materials may adequately function as a casing layer, it is widely accepted that a sphagnum peat, when neutralised with chalk or limestone, is the most suitable medium. Its unique water-holding and structural properties are widely accepted as ideal for the purposes of casing. In Great Britain, peat has completely replaced soil as a casing medium for almost three decades but in the intervening years comparatively little attention has been given to understanding its function and the reasons for its superiority. Even less attention has been given to obviate the disadvantages, which are increasingly becoming apparent as more emphasis is given to mushroom quality and to the economics of production methods. This applies especially to aspects related to harvesting the mushroom crop and its subsequent handling, storage and transport to the point of sale.

In addition of these inherent disadvantages, supplies of peat are not infinite; for example it is estimated that supplies of peat in Eire, the main source of peat for the British mushroom industry, may be depleted in less than three decades. An alternative casing medium, which is at least as productive as peat, is a desirable objective for the longterm stability of commercial mushroom culture.

Although water-holding capacity and structure are primary requirements of a good casing (Bels-Koning, 1950; Edwards and Flegg, 1953; Flegg, 1959; Reeve et al.; 1959), investigations on the properties of a productive casing (Hayes, 1972, 1974; Hume and Hayes, 1976) have led to the firm conclusion that an appropriate bacterial flora and chemical composition are important secondary requirements. This is particularly so, if a greater degree of standardisation is required in the control over such factors as number per unit area, size and pattern of cropping. Quality characteristics of the harvested crop are related to all requirements, physical, chemical and biological.

Considerable difficulty has been experienced in past investigations in defining the chemical characteristics of soils based on peat. This is largely due to the complex organic nature of peat and to the difficulty of extracting and monitoring components which may influence processes concerned with the physiology of growth and development of A. bisporus. This is likely to prove crucial in achieving standardisation and control over cropping.

In this report, the characteristics of a by-product of a large paper and pulp mill in England (Kemsley Paper Mill, Sittingbourne, Kent) are described and discussed as an alternative material to peat as a main ingredient of a casing soil for commercial cultivation in Great Britain. Some features are emphasised as being advantageous and its value in the study of some factors associated with crop development are illustrated.

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