PEDO-AGRONOMIC AND ENVIRONMENTAL ANALYSIS OF SOME AGRICULTURAL SOILS OF KEUR-MACENE SOUTH OF MAURITANIA

Mauritania is a country with a rather agricultural vocation. Apart from irrigated areas and agribusiness, agricultural activity is dominated by traditional agriculture and nevertheless remains confronted with several challenges: poverty affecting the rural world, dependence of the sector on climatic hazards with irregular rainfall and, finally, insufficient yield and agricultural production. Faced with this situation, improving the agricultural sector comes first through improving the state of fertility of agricultural soils and setting up agriculture adapted to climatic conditions and local market requirements. The purpose of this study is to assess the physicochemical fertility of seven ricegrowing soils in the city of Keur-Macène, Mauritania, and to identify the various physico-chemical constraints likely to paralyze or limit their productivity. The physicochemical analyzes of these soils and the evaluation of their fertility indices show that the superficial horizons 40 cm deep have a sandy-silty to silty texture with a slightly acidic to slightly alkaline pH (pH close to neutrality, and an electrical conductivity evoking a high salinity. The soils showed overall organic matter contents above the average threshold value proposed by the literature. However, there is a total nitrogen deficiency and a C/N ratio greater than 15 with the exception of soil 5, which highlights a low biological activity and a poor mineralization process and therefore a low liberalization of the quantity of nitrogen in the soil. The concentrations obtained for the available phosphorus in all the studied soils are higher than the threshold value recommended in the literature. The results recorded for our soils also showed that the rate of cation exchange capacity (CEC) is low to medium for all the soils studied. Among the exchangeable bases, sodium Na + is the most abundant cation followed by Ca2 +, K + and Mg2 +. For minor nutrients or trace elements, Cu, Mn and Zn showed levels lower than indicative toxicity values but strong anomalies were identified for Fe, However, the contents of toxic metals Cd, Pb and Hg are all below the tolerated threshold values.