The Biological Decomposition of Plant Materials Part Viii. The Availability of the Nitrogen of Fungal Tissues

SUMMARY. Various aspects of the availability of the nitrogen, of fungal tissue to micro‐organisms have been investigated, with particular reference to the influence of the C/N ratio of the material. Fungal tissue was found to be as suitable a source of nitrogen as ammonium salts and nitrates for the decomposition of straw both by a mixed soil flora and by pure cultures of certain fungi. The liberation of ammonia in sand culture from fungal tissue by pure cultures of reputedly active ammonifiers was measured. The nitrification in soils of a number of samples of fungus tissue was compared with that of artificial mixtures of equal C/N ratio built up from glucose, cellulose and straw, each with added inorganic nitrogen. A very clear correlation was found between the C/N ratio of the fungal material and the nitrogen nitrified. In one series in hill‐side soil nitrification increased from 42 to 80 per cent, in 6 months as the ratio decreased from 15.8 to 5.5; in another, from 20 to 75 per cent, as the ratio decreased from 17 to 7. No evidence was found for the existence of a very resistant and unnitrifiable residue from fungal tissue as claimed by some workers, and incomplete nitrification is probably due to the attainment of biological equilibrium or of a state in which change is very slow.