How commercial rhizobial inoculants can contribute to improved livelihoods of resource poor African farmers

There is a proliferation of commercial bioinoculant products appearing on the market that claim major impact in increasing crop productivity without any scientific assessments about their effectiveness in the field. TSBF-CIAT has been mandated by Bill and Melinda Gate Foundation to scientifically evaluate and select effective commercial products for improving and sustaining crop yields in selected agro ecological zones in 3 African countries. Our results on about 120 products showed that many private companies commercialize a mix of non-defined microorganisms and thus do not ensure the quality of their inoculants. This may explain their lack of impact on the plant growth even under controlled greenhouse conditions. Generally, high level of contamination was observed as pure products represented only 33% of the products, 41% of the products contained all the expected strains and 52% of the products contain none or part of the expected contaminants. We assessed under greenhouse conditions the possible effect of the formulation of effective rhizobial inoculants on both soybean growth and nodulation. Our results showed that there was no effect and the association of the rhizobia with a Bacillus strain didn't induce any significant stimulation of soybean growth. However, through field demonstration trials combining rhizobia with mycorrhiza and P solubilizing bacteria, our results suggested some relevant positive interactions on soybean yield. In Kenya, we tested one rhizobial inoculant in 3 mandates areas (about 50 farms in each) and our results demonstrated a significant effect of the inoculation on soybean yield. The next step will consist of making such effective inoculants cheap and available on the local markets. Administrative issues shall be sorted out for each country as the national regulations are not similar and of course the quality control issue shall be taken into account to ensure the viability of the inoculants to farmers who purchase them. (Texte intégral