Notes on the distribution and effectiveness of cowpea Rhizobium in Nigerian soils

Summary and conclusion

Preliminary investigations were conducted to assess the distribution and effectiveness of cowpea Rhizobium in the soils of Nigeria. Pure cultures of Rhizobium isolated from 13 representative farming districts were used to inoculate cowpea seedlings in sterile, nitrogen-free sand culture. Inoculation resulted in nodulation and nitrogen accretion in the plants while uninoculated plants died shortly after emergence. Although variable, the results indicated that effective strains of cowpea Rhizobium were present in the soils from the 13 locations. This observation might have some significance to cowpea production in Nigeria particularly in respect of the nitrogen nutrition of the crop. Further investigations will however be necessary in order to evaluate more fully the variability in effectiveness of cowpea Rhizobium under the environments of Nigerian agro-ecological zones.