Chemical sterilisation

Abstract

By comparison with mineral soils, many of the materials used to make loam-less composts can be considered already sterile as far as plant pathogens are concerned. Some materials, such as foam plastics, perlite and vermiculite have been subjected to very high temperatures during their manufacture and have virtually been sterilised already. Whilst many peats are free of pathogens, some samples may contain Rhizoctonia, and some bark samples may be infected with Phytophthora cinnamomi. The incidence of fungi in composts made from peat is, however, normally low, and it is common practice in Britain not to treat peat with heat or chemicals except when growing certain crops which are particularly susceptible to soil-borne diseases. For example, peat used for cucumber propagation is often heat sterilised or treated chemically against Pythium attack; antirrhinum is another plant which is susceptible to Pythium. Tomato, chrysanthemum and French marigolds are examples of plants which are not particularly susceptible to soil-borne fungal attacks.