History of Rhizobia Inoculants Use for Improving Performance of Grain Legumes Based on Experience from Nigeria

Abstract

The use of rhizobium inoculants for improvement in nitrogen-fixation and productivity of grain legumes has been well established in developed countries. However, the practice is still under-utilized in Nigeria. Nitrogen (N) is the most frequently deficient nutrient for crop production, while nitrogen fertilizers are costly, inadequate, and may not be timely in supply. These make rhizobia inoculants a cheaper, easier and safer option to improve the N2-fixation and productivity of grain legumes. Inoculant use in Nigeria was initiated in the 1970s, but still remains very limited. Studies conducted on inoculant use were initially on “US type” Soybean (Glycine max (L.) Merrill), which has been found to require specific inoculation with Bradyrhizobim japonicum for optimum productivity. Studies were also conducted on inoculation of cowpea (Vigna unguiculata (L.) Walp), but rarely on bambara groundnut (Vigna subterranea (L.) Verdc.) and groundnut or peanut (Arachis hypogaea L.). In the 1980s, the International Institute of Tropical Agriculture (IITA) Ibadan, Nigeria, introduced promiscuous soybean cultivars; Tropical Glycine Cross (TGx). These genotypes nodulate freely with the indigenous rhizobium population, fix large amount of atmospheric nitrogen and produce higher grain yields than the local genotypes. However, some experiments indicated up to 40–45% increases in yield by some of the genotypes on inoculation. Hence, the ultimate solution remains the development of inoculants using highly effective indigenous rhizobia strains for particular crops. The recent efforts of the project “Putting Nitrogen fixation to work for smallholder farmers in Africa (N2Africa)” towards the promotion of inoculants technology are highly welcomed in the country.