Physico-chemical properties, initial microbial population and survival of rhizobia in peat, vermi¬culite and filtermud

Abstract

Carrier materials are an important compo¬nent of legume inoculants, both in protect¬ing and applying the rhizobia. We have measured selected physico-chemical prop¬erties, initial microbial populations (bacte¬ria, actinomycetes and fungi) and survival of rhizobia introduced to peat, vermiculite and Muhoroni filtermud. Peat and vermi¬culite were collected from Ondiri and Kajiado respectively. Both sources are readily accessible from Nairobi, the loca¬tion of the MIRCEN legume inoculant pro¬duction facility. Peat was acidic while filtermud and vermi¬culite were close to pH 7.0. Filtermud and peat recorded high carbon while vermi¬culite contained low level of nitrogen as compared to the other two carriers. The original microbial populations in peat and filtermud were approximately lOa-fold greater than in vermiculite. Peat and filter¬mud supported the rhizobial densities of upto 108g-1 for six months which was the duration of the experiment. The results indicate that Ondiri peat would be a suit¬able substitute for rhizobia inoculant pro¬duction, having properties which compare favourably to the filtermud.