ABSTRACT
This study was conducted in the University of Benin, Benin City, to determine the status of heavy metal and some plant nutrients at two depth (0-15 cm and 15-30 cm) under four different land use types (Arable, lawn forest and sport land) in the University of Benin, Benin City. The experiment was laid out in a randomized complete block design (RCBD) with two variables (land use and depth). Soil samples were collected at depth 0-15 cm and 15-30 cm from twelve spots, three each from four land use type namely; Arable, lawn, sport and forest land. Soil samples were collected with soil auger, then air-dried for laboratory analysis. Laboratory analysis were done using standard procedures. Some parameters analyzed for were particle size distribution, pH, total organic carbon (TOC), concentration of Iron (Fe), Manganese (MN), Zinc (Zn), Copper (Cu), Cadmium (Cd), Chromium (Cr) and Lead (Pb). Data obtained were subjected to analysis of variance (ANOVA), while Duncan's New multiple range test was used to seperate means at 5% level of significance. Results shows that the textural class of the soil were generally sand at depth 0-15 cm and loamy sand at depth 15-30 cm. While the pH were generally acidic ranging from 5.33 in Arable to 5.79 in forest at depth 0-15 cm, and 5.16 in sport to 5.31 in forest land at depth 15-30 cm , TOC decreased with depths, ranging from 11.77 g/kg in sport to 26.57 g/kg in forest at depth 0-15cm and 6.420 g/kg in sport land to 13.433 g/kg in forest land at depth 15-30 cm. For the essential heavy metals (Zn, Mn, Cu, Fe), all recorded their significantly (P<0.05) highest values in the lawn (31.27 mg/kg, 20.70 mg/kg, 34.37 mg/kg and 67.43 mg/kg respectively). The least Zn xii (19.20 mg/kg) and Cu (25.40 mg/kg) were recorded in the sport land while the least Mn (13.90 mg/kg) and Fe (58.33 mg/kg) were recorded in the forest. In the 15- 30 cm depth, the highest significant (P<0.05) Zn, Mn, Cu and Fe (25.43 mg/kg, 17.40 mg/kg, 26.07 mg/kg and 58.17 mg/kg respectively) were recorded in the lawn. For non-essential heavy metals , Pb was detected in top 15cm of the lawn, forest and arable land but was not detected in the sport land use with it's highest (0.077 mg/kg) and least (0.00 mg/kg) recorded in the lawn and sports land uses respectively. In the 15-30 cm depth , Pb was only detected in the lawn. Cd was only present 0.007 mg/kg and 0.010 mg/kg in the top soil of lawn and forest respectively. While Cr was only detectable in the top 15cm of the lawn. The heavy metals content were below the permissible limits in the soil under.
