The aim of this invention is the development of an essentially new method for production of a casing layer (casing) intended for cultivation of mushrooms/plants and the use of appropriate equipment for this purpose. The invention allows the abandonment of raw materials with desired structure and enables making of preferred structure by using locally available low-quality raw materials, which is particularly relevant for countries having no raw materials suitable for the production of mushroom casing. The essence of this method is that a raw paste of ingredients is subjected to mechanical action and in the course of this action extra fibres are gradually added to the paste, fibres which quickly enter the inside of the paste and carry out the function of binding of the material being mixed (primary conglutination). Under continued mechanical action and by adding the rest of the said fibres, agglomeration of formed crumbles occurs (secondary conglutination). Thus agglomerates are formed that are later used to build the casing characterized by desired structure and resistance to mechanical action and virtually independent of the structure of raw materials used. Furthermore, this method offers the possibility to shape the casing surface to give it the desired relief (e.g. wavy surface).