A MICROBIOLOGICAL STUDY OF PODSOL SOIL PROFILES: II. LAURENTIAN SOILS

Abstract

Microbiological studies of samples from the separate horizons of two soils from the Laurentian uplands showed that, as in the case of the soils previously studied from the Appalachian uplands, biological activity was dependent upon the organic-matter relations of the horizons. A1 (organic-matter) horizons were the most active, as shown by the evolution of carbon dioxide, nitrification of the soil's own nitrogen, by numbers of micro-organisms (bacteria, actinomyces, and fungi) and by the production of ammonia from urea. Bacterial numbers in the illuvial horizons were, however, higher than in the eluvial (leached) horizons above, a condition that did not obtain with the Appalachian soils. The organic matter of a soil bearing a coniferous (spruce) flora was deficient in nitrifying power. The biological activity at different levels of a virgin clay soil was found to be in sharp contrast with that of the podsol soils.