MICROBIOLOGY OF PEAT

Speaking hereabout the microbiology of peat I want to state at the beginning that the term peat means two completely different kinds of material: the undisturbed peat on the original site and the harvested and piled peat on the other hand. These two materials are so different in their physical and biological properties and consequently to a certain extent in their chemical behaviour that, when talking about them, they should be clearly separated and not be mixed up.

At this conference I shall restrict myself to some comments on the microflora of milled peat as this is mainly used for horticultural purpose.

The natural peat contains a considerable number of microorganisms; owing to the high acidity of peat fungi are in the majority, but also actinomycetes and bacteria (e.g. Pseudomonas) have been found which are adapted to this extreme habitat (Waksman/Purvis, 1932; Beck/Poschenrieder, 1961). All these figures presented cannot be generalized because each individual peat varies in its chemical and consequently also in its microbiological composition. With regard to the Irish peat and boglands I want to remind you of the studies of Walsh/Barry (1958), Moore (1954), Küster (1963a, 1969), Dickinson/Dooley (1967, 1969, 1970),

The microflora of peat consists of a small number of genera and species only. Most of the organisms present are in a dormant or resting state. The microbial activity in bogland is very small and slow. The entire situation is completely changed when the peat is harvested by milling and piled. By these procedures the aeration and other physical factors are improved. The number and activity of microorganisms increase. The quantitative and qualitative composition of the microflora of milled peat depends largely on its quality, i. e. the content of available nutrients and energy sources. The more decomposed, humified and carbonised the carbon material in peat, the smaller the content of utilisable compounds and less available they become for microbes. The poorer the quality of peat with regard to its use as fuel, the higher are the figures for microorganisms as obtained by the plate count method (Küster, 1963b) (table 1).

Poor quality is equivalent to low decomposition. Poor peat still contains organic matter which can be used by microorganisms. It has been demonstrated that the less-decomposed layers of high moor contain more hemicelluloses and celluloses than the well-decomposed ones (Waksman/Stevens, 1928; Theander, 1954).

We can conclude from this that a microbial activity is quite well evolved in less-decomposed peat, this is particularly obvious when remains of the surface layer with root residues are mixed into the peat