Characterization and Integrated Assessment of the Chemical Fertility of Oasis Soils in Southeastern Niger

This study, conducted in the oasis basins of the Gouré, Goudoumaria, and Mainé Soroa departments (southeastern Niger), aims to characterize the soils in terms of morphological and physicochemical properties in order to assess their fertility. Nine (9) soil profiles were opened, and nine (9) soil samples were analyzed at the INRAN LASEVE laboratory using standardized methods. The results show a texture varying from sandy silt to silty clay depending on the depth for the Toumourwa, Balla, and Bassori basins, with a basic pH between 8.1 and 8.9 and moderate electrical conductivity indicating low salinity. The organic matter content (0.47 to 2.62%), available phosphorus (< 5 cmol+/kg), and cation exchange capacity (1.75 to 13.25 cmol+/kg) generally indicate low to medium fertility. The study reveals three groups of basins: High fertility basins: Tissouwa, Balla, and Toumourwa with organic matter (OM) > 1.5%, cation exchange capacity (CEC) > 8, and balanced pH; Medium fertility basins: Adébour, Bassori, Tchéballam, and Gotanga with average cation balance, low organic matter content, and good chemical reserve; Low fertility basins: Goudoumaria North and Kiria Mandaram with low CEC and OM, and degraded soil structure. Fertility can be improved through the application of compost, mulching, crop rotation, and sustainable water management. These practices are essential for restoring the productivity of oasis soils and strengthening local food security.