Abstract:
An attempt was made to find an economic alternative for peat moss which is currently used as casing material in the commercial production of Agaricus brunnescens Peck. Substrates such as spent compost which is obtainable from various farms, and paper pulp, as well as additives like vermiculite and activated charcoal, were evaluated. Certain chemical, physical and microbiological aspects as well as the production of mushrooms and the average number of fruit bodies per unit area obtained on the various substrates, were compared with peat moss. The percentage water-holding capacity, percentage pore space, pH, conductivity, number of fungi and number of bacteria per gram dry mass of the materials were determined. Fungi were isolated from these materials and identified with the aim of tracing possible competitive and parasitising fungi. In addition fresh spent compost was allowed to mature for a period of one year in the veld and was artificially leached by regular watering. Any changes in the above mentioned aspects as well as changes in the production of mushrooms by using compost as casing material were noted. The production on spent compost that was spread out in the veld under South African weather conditions and artificially leached, compared favourably with that of peat moss. The conductivity and number of bacteria in the matured spent compost showed a drastic reduction during this period, while the production increased. Spent compost left in the veld for two years to leach but without spreading it, did not give such a high yield. An increase in production was achieved by adding 2,6% activated charcoal to the spent compost. The physical properties of the casing material do not necessarily improve by adding 15% and 30% of vermiculite. Production when paper pulp was used as casing material was quite significant initially but the paper pulp probably cannot maintain this level of production over a long time span of five breaks. Only three fungi which probably parasitise mushroom miselium were isolated from the evaluated material, namely Mycogone perniciosa from fresh used compost and Chrysosporiumcf. pannorum and Verticillium fungicola from the peat. Futhermore a number of green moulds (possibly could be in competition with the mushrooms) were isolated, namely species of Aspergillus, ciadosporium, PeniciZZium and Trichoderma. None of these fungi affected the mushroom growth adversely.
