EFFECT OF COMBINED NITROGEN ON FIXATION OF ATMOSPHERIC NITROGEN BY BEIJERINCKIA

Abstract

Peptone, urea, ammonium sulphate and sodium nitrate were added, in different amounts, to a nutrient medium which was inoculated with several strains of Beijerinckia indica from soils in different parts of India. The medium was incubated at 30° for fourteen days after which the nitrogen contents of the culture liquids were determined.
It was observed that addition of nitrogen through these substances had an inhibitory effect on nitrogen fixation.
The highest rate of depression of nitrogen fixation was observed in the case of sodium nitrate and the lowest in the case of urea.