Potential of Native Rhizobia Isolates to Improve Production of Legume Crops in Small Holder Farms

Abstract

In sub-Saharan Africa, crop production has continued to decline due to soil infertility, limited arable land, among other factors. This has necessitated the use of inorganic farm inputs, which are expensive and have detrimental environmental effects. Rhizobia technology can enhance legume crop production. The present study aimed at assessing the potential of native rhizobia isolates from different Kenyan agro-ecological zones to enhance legume production. Native rhizobia were isolated from root nodules of cowpea grown in soils from Embu and Tharaka Nithi counties. Based on morphological and biochemical characteristics, 53 bacterial isolates were identified and placed into 11 groups. The isolates were tested for symbiotic efficiency in the greenhouse using Glycine max, Vigna unguiculata, and Vigna radiata grown in sterilized and unsterilized soils. The treatments comprised native rhizobia isolates, commercial rhizobia inoculum and un-inoculated control. The experiments were laid out in a completely randomized design with four replicates. Remarkably, forty five rhizobia isolates induced nodulation and influenced the growth of the test crops. Symbiotic efficiencies differed among the isolates (p<0.05) in all the crops. There was a significant difference on growth parameters between sterilized and un-sterilized soils after inoculating the test crops with native rhizobia isolates (p < 0.05). Some native rhizobia isolates such as IsAS11, IsM and IsAS14 performed similarly to the commercial inoculum in soya bean, cowpea and green gram. These findings demonstrate the potential use of native rhizobia isolates in the development of low-cost bio-fertilizers for enhanced smallholder legume production.

Keywords: Rhizobia; Inoculation; Legume Crops; Biological Nitrogen Fixation; Smallholder Farms