This research showed positive effect of A. senegal on soils total microbial activity on different sites in Niger. Soils were sampled under and outside A. senegal crown. The depth of soil sampling is 0-25 cm. sites that samples take out are: Azzai, Bader, Malam Maimari, N’Guel kolo, Kokoye and Kiki. Activity was greater on soils under A. senegal crown, than outside crown. Results showed strong correlation between total microbial activity and soils physico-chemical parameters. Correlation was positive on soils with higher clay content, and negative on those with higher sand content. Thus, under A. senegal crown, soils total microbial activity was significantly different between studied sites. Activity on Kiki’s site with value of 5,9 µg/g/h, was twice that obtained at N’Guel kolo. On all sites, total microbial activities on soils outside of A. senegal crown, was either a third lower (Kokoye and N’Guel kolo), or half lower (Kiki, Malam Maimari, Bader and Azzai), than under the crown. A. senegal is legume plant, that can contribute to fertilize and stabilize poor soils. A better valorisation of A. senegal would allow development of agroforestry system in nitrogen deficient soils of the Sahelian zone. Agroforestry practices could increase plant diversity, control soil erosion and sequester organic carbon.