Improvement of the chemical properties of waste rock deposits at the Agbaou gold mine by the legume Pueraria phasoeloïdes (Center-west Côte d'Ivoire)

Objective: To assess the effects of the legume (Pueraria phasoeloïdes) on the chemical parameters of the waste rock soils (saprolites) at the Agbaou gold mine, in the center-west of Côte d’Ivoire.

Methodology and results: Soil samples were taken using the systematic sampling method at regular intervals of 20 m on the ramps and at 20 cm soil depth, using an auger during two consecutive sampling campaigns (2016-2017 and 2017-2018). The geometric coordinates of the sampling points were obtained using a GPS Garming CSX60 type. A total of 20 composite samples were made from 80 collected soil samples. Chemical analyzes were carried out on soil samples obtained. The results show that the contents of total organic carbon (TOC), total organic nitrogen (Nt), the C: N ratio and the pH values of the soils, under Pueraria phaseoloïdes legume were significantly improved between the ramps and between the two campaigns (p <0.05). Conversely, (CEC, exchangeable bases, (Ca2+, Mg2+ and K+) and phosphorus contents decreased significantly (p <0.001) between the ramps and the two campaigns. This reflects the improving effect of the legume on the chemical parameters of the soils. However, variations in trace element content between ramps and across campaigns did not show any significant improvement (p> 0.05).