Nitrogen Fixation by Blue-Green Algæ

Abstract

IN India, rice is grown on the same land for many years without the addition of manures to the soil. Preliminary experiments have shown that a considerable amount of nitrogen is fixed in the soils of the rice-fields under water-logged conditions, when there is an abundance of algal growth (especially Blue-green Algæ) present. With the object of investigating the role of the Blue-green Algæ, a number of species of Anabœna, as well as Phormidium foveolarum, were isolated in unialgal culture from the soil of an Indian rice-field. The last, as well as three species of Anabœna, were afterwards obtained in pure culture, altogether devoid of bacteria and other contaminating organisms, by a method analogous to that employed by Pringsheim (1913). These cultures have been tested by the Bacteriological Department at the Rothamsted Experimental Station and pronounced free from bacteria.