PERLITE AS A CARRIER FOR LEGUME INOCULANTS

Obtaining thin-powdered inoculants by using a new carrier material, na mely an aluminosilicate known as perlite, is discussed, Normally, perl ite is used as a co-filter in many industrial processes. A comparative study between perlite and pear as a carrier has been carried out, Mic robial suspensions of Bradyrhizobium japonicum and Rhizobium meliloti, grown in either a yeast extract medium or an amaranth meal medium, we re used to prepare inoculants. Two initial concentration levels, 10(10 ) and 10(7) viable cells x ml(-1), respectively, were used for impregn ating carriers. 200-mesh screened carriers were used, Suspensions were grown in Erlenmeyer flasks mounted on a rotary shaker, Survival rate was determined for prepared inoculants, After six months, the physiolo gical behavior of the strains in specific plant varieties was assessed . Results suggest that (a) perlite can substitute for peat in the prep aration of inoculants, and (b) amaranth meal-containing media allow hi gher concentrations be obtained on the carrier. Six months after inocu lants had been prepared, all samples showed microbial concentration hi gher than 7 x 10(8) viable cells x g(-1), a value in keeping with inte rnational standards requirements, with the strain maintaining its symb iotic properties. Results are all the more promising since perlite is a low-cost material and, as it is free from contaminating agents, ther e is no need for sterilization.