Soil Health Evaluation of Some d-block Metals in Selected Agricultural Soils in Southeast Nigeria

Abstract

Abstract Synergizing soil fertility, soil health and environmental management through the careful use of soil amendments and controlled discharge of wastes to the environment is needed for environmental safety. The study investigated the concentration, fertility and potential health risks of Ti, V, Fe, Mn, and Mo in some agricultural soils, and evaluated the relationship between the metals and some soil properties. Digital elevation models (DEMs) at 30m × 30m spatial resolution of Ishibori, Agoi-Ibami and Mfamosing, Cross River State, Southeast-Nigeria, were obtained. Eight elevation ranges resulted from the DEMs and one soil profile pit was sunk along each of NG1, NG2, CG1, CG2, CG3, and SG1, SG2 and SG3. Thirty-five composite soil samples were collected at predetermined depths of 30 cm and processed for laboratory analysis. Among the five studied metals, the profile means of Mn (660.82 ± 612.89 mg/kg) and Mo (2.61 ± 0.73 mg/kg) exceeded permissible concentrations and would pose threats to the environment. Also, Ti, V, and Fe concentrations exceeded their permissible values in NG1 and NG2, making the soils most prone to toxicity. The metals were irregularly distributed with depth, however, Mn and Fe were either concentrated in the subsurface or values increased continuously with soil depth. Clay and sand contents correlated positively and negatively with all the studied metals, while organic carbon and exchangeable Ca were not correlated at p < 0.05. All the models were within the range of 33 – 67 % for R2. The best performing functions were V and Mo, while bulk density, organic C, total N, Na and K were the most influential variables in PC1.