Symbiosis and ecological adaptation of the commercial nitrogen fixing bacteria on underutilized Bambara groundnut crop.

Abstract

The efficiency of the natural symbiotic relationship between communally produced legumes and nitrogen fixing bacteria has been reported to be very poor, mainly due to poor soils in communal farming areas. With the use of synthetic fertilizers to increase soil fertility being both environment-unfriendly and unaffordable for majority of communal farmers, strategies that are cost-effective and climate smart need to be put in place to improve the productivity of communal legumes such as Bambara groundnuts. A 5 x 3 factorial arrangement experiment in a randomised complete block design with five replications was established under greenhouse conditions. Factors consisted of bacterial species: [Bradyrhizobium japonicum (Bj), Rhizobium loti (Rl), Rhizobium meliloti (Rm), Rhizobium leguminosarum biovar phaseoli (Rlt) and a negative control (untreated)], and local Bambara groundnut varieties: black, creamy white-eye, and red. Bambara groundnut seeds were inoculated with levels recommended for cowpea and soyabean. Nitrogen fixing bacteria application on Bambara groundnuts increased plant growth and nodulation variables, with the effects varying with Bambara groundnut variety and rhizobium type. Bj outperformed the other tested bacteria on nodulation variables, with the red cultivar performing better in all growth variables, making it suitable for pod and vegetative production.