Department of Agricultural Chemistry and Soil Science, Bidhan Chandra Krishi Viswa Vidyalaya, Kalyani, West Bengal, 741235
*Present address: Department of Agricultural Chemistry, State Agricultural Research Institute, 230 A, Netaji Subhas Chandra Bose Road, Calcutta, West Bengal, 700040
Three strains of Azotobacter chroococcum in slants and broth culture were incubated at soil surface and at different depths in the same field from where the strains had been isolated. The growth characteristics (elevation, spreading and cell mass) and pigmentation of the strains in slants were better expressed in the 5 to 15 cm soil depth than at the surface, followed by a decline at still lower depths. The depth of the soil exerted a differential influence on the proliferation and efficacy towards nitrogen fixation of the strains in broth culture. In general, under favourable nutritional, moisture and pH conditions, nitrogen fixation way the highest at 10 cm depth followed by that at 20 cm and the lowest at 30 cm depth in the soil.
Azotobacter growth, nitrogen fixation, soil depth
