Decomposition of Blue-Green Algae as Effected by the Action of Soil Bacteria

Abstract

Several years ago, one of the present authors (Watanabe) presented a method for improving the fertility of paddy fields by the use of nitrogenfixing blue-green algae as “green manure” (i). The effectiveness of this method has been proved by large-scale tests carried out on the crop yield of rice plants during the period from 1951 to 1956 at eleven experimental farms in various parts of this country; in fact, the increase in the crop attained by applying this method was, on an average, as much as 20 per cent in the final steady state (2-4). However, in these experiments, it was also found that the effect of the algae on crop yield was variable from one field to another, even when an equally active growth of the inoculated algae was observed in the test fields. Since it is reasonably inferred that algal nitrogen is utilized by the plant as N-source after its conversion by the activity of soil bacteria into an inorganic form such as ammonia or nitrate, the fact mentioned above indicates that the nature of the bacterial flora already present in the field is an important factor in applying this method successfully in agricultural practice. © 1959, Applied Microbiology, Molecular and Cellular Biosciences Research Foundation. All rights reserved.