A short communication: Response of Soybean to concomitant inoculation with Arbuscular Mycorrhizal fungi and Rhizobium

Low soil fertility especially N and P limits soybean production among the resource poor farmers in Kenya. A combination of effective rhizobia and arbuscular mycorrhiza fungi (AMF) inoculants can be used to alleviate these deficiencies. In this study, the response of soybean variety, Gazelle to 2 AMF species (Acaulospora sp. and a Glomus sp.) and a rhizobium inoculant (Bradyrhizobium japonicum) was evaluated. Soybeans seeds dressed with rhizobium were planted in sterilized soil infested with 20g of AMF inoculum. Plant growth parameters (dry shoot and root weights, total dry weights and number of pods), number of nodules and percent root colonization by AMF were assessed 10 weeks after inoculation. Growth responses and mycorrhizal dependency of soybean were also computed. Both AMF and rhizobium when applied singly, had no significant effects on the growth of soybean. A combination of both the rhizobium and Glomus sp. significantly reduced soybean growth while a combination of Acaulospora sp. and rhizobium had no significant effects on the growth of soybeans. Bradyrhizobium japonicum significantly reduced root colonization by Acaulospora sp but had no effect on root colonization by the Glomus sp. Key Words: Arbuscular mycorrhiza fungi, rhizobium, soybean J. Trop. Microbiol Vol.2 2003: 35-39