M. REVATHI AND K. VENKATESWARLU
Abstract
Viable population of autotrophic nitrifiers, enumerated by the most-probable number method, was more pronounced in rhizosphere soil obtained from groundnut than in non-rhizosphere soil. Among different growth media tested for autotrophic ammonia oxidizers and nitrite oxidizers, the modified Winogradsky's medium was found to be the best choice. The rate of either ammonium oxidation or nitrite oxidation by the native population of nitrifiers was significantly higher in the rhizosphere soil of groundnut than in non-rhizosphere soil. The metabolic activity of ammonia oxidizers or nitrite oxidizers was proportional to the concentration of soil inoculum included in the modified Winogradsky's medium.