in the cultivation of mushrooms from an underlying bed containing mushroom spores , novel compositions and processes are provided for a casing layer which is placed over the compost layer containing spawning mycelium . a hydrophilic , thermosetting prepolymer resin is mixed in with a casing substrate , preferably canadian peat , other optional additives and sufficient amount of water to form a slurry and the mixture is allowed to cure to a spongy block . the cured material is then pulverized and deposited as a casing layer over the compost layer . because of the high water retention qualities of this material , watering the mushroom beds is reduced by a factor of three or more , thereby reducing operation and production costs , as also the incidence and severity of disease and displeasing blemishes .