Global Landscape of Organic Carbon and Total Nitrogen in the Soils of Oasis Ecosystems in Southern Tunisia

Abstract

The oasis soils of Tunisia face several climatic and soil constraints. Trying to have cultures that are profitable and beneficial in terms of soil C and N sequestration in such environments is already a challenge. To conduct this, we tested under identical conditions four types of occupation in sub-plots adjacent to the crops; barley alone, alfalfa alone, intercropping barley/alfalfa, and a control fallow in a saline gypseous desert soil poor in organic matter. Field experimentation was carried out in the oasis of Degache, which is very representative of other Tunisian oases. The stocks of C and N of the plot were calculated from the start in September 2019 before the installation of the different crops. After 21 months, the control plot shows a decrease of −41% in its stock of C and −25% in its stock N. However, the best result is that of the barley/alfalfa intercropping with an increase of +126.46% in the C stock and +178.67% in the N stock. After almost two years of experience, the beneficial effect of the intercropping system in the oasis is clear. These results are very motivating and seem to be a solution to the rapid decline in soil organic stocks.