Multiplication and Viability of some Rhizobium Strains to be used as Inoculants for Agricultural Biomass Production

Abstract

Rhizobia are well known for their capacity to establish a symbiosis with legumes. They inhabit root nodules, where they reduce atmospheric nitrogen and make it available to the plant. Biological nitrogen fixation is an important component of sustainable agriculture, and rhizobial inoculants have been applied frequently as biofertilizers. In this review we approach the subject of legumes inoculation in order to improve the nitrogen fixing capacity. In the first part of the experiment, the Rhizobium strains were cultivated on media indicated in the literature as optimal for bacterial growing and development in laboratory conditions. Afterwards, the Rhizobium strains that have grown and accumulate biomass were tested in different conditions of pH and salinity. The biomass accumulation was determinate by spectrophotometer. The obtained values shown that the Rhizobium strains tested can be used to inoculate the legumes cultivated on acid, basic and alkaline soils. Finally, the stability in real time of two strains of Rhizobium (Rhizobium meliloti and Rhizobium japonicum) mixed with different supports was evaluated during a 6-months period. The supports studied were: peat, peat and calcium carbonate, zeolite, and ceramic.  The highest number of viable cells at the end of the experiment was obtained in ceramic with Rhizobium japonicum (8x10⁵ cells/gram), and the lowest number of viable cells was obtained in zeolite with Rhizobium meliloti (1,1x10³ cells/gram).