Abstract
The following experimental data was compiled after investigation the microfloras of soil types located in the Tokachi district, Hokkaido, by means of the cultural plate count method. The soil types employed were Brown volcanogenous soil (BrVS), Black volcanogenous soil (BlVS), Brown forest soil (BFS), Pseudogley soil (PGS), Stagnogley soil (SGS), Alluvial soil (AlS) and Peat soil (PS). The soil micro-organisms investigated were Fungi (F), Bacteria (B), Actinomycetes (A), Gram-negative bacteria (GN) and Anaerobes (An). The results are summarized as follows: 1) Each microbial count of all soil types became low from the upper to the lower horizon, but degrees of decrease with depth varied among microorganisms and among soil types. 2) The degree of decrease with depth of microbial count in (BFS) was the most gradual. The next was in (BrVS). But (PGS) and (SGS), which had soil profiles with great variation in chemical and physical characteristics, were steeply. Although (AlS) had a soil profile with little variation in its chemical and physical characteristics, it too decreased steeply. 3) (A/B) of volcanogenous soils were higher than that of non-volcanogenous soils as a whole. Among the volcanogenous soils, the ratio was higher in (BrVS) than that in (BlVS), and among the non-volcanogenous soils, higher in (BFS) than (PGS). 4) The variation of (GN/B) among upper horizon of the soil types was comparatively small. In deeper horizon, the variation of (BrVS) was less, and those of (AlS) and (PS) higher. The conclusion to be reached from these results show that microbial phenomena have an intense correlation with the many types of soil characteristics. It also contends that the soil classification system is the most systematic approach available in investigating soil micro-organisms.
