Abstract
Contrary to the increased alarm that nickel is a soil pollutant, nickel is an essential micronutrient for the growth and development of legume and cereal crops. This study was carried out to assess the status of nickel (Ni) in four different soils under cultivated, fallowed, forest and dumpsite land use and determine the best extractant to be used for Nickel extraction from soil solution. Twenty-four (24) bulk surface soil samples (0-20cm depth) were collected from the four different land use types within the University of Ibadan campus. Available nickel was determined using four different extractants (1N NH4 OAc, 0.5N CH3 COOH, 1N HCl and EDTA) and the concentrations were read using Atomic Absorption Spectrophotometer (AAS). The experimental design employed for the screen house experiment was Completely Randomized Design (CRD). EDTA extracted the highest nickel concentration (37.73 ±1.47 mg/kg), followed by 1N HCl (31.31 ± 1.50 mg/kg) and 1N NH4 OAc (24.26 ± 1.05 mg/kg), while 0.5N CH3 COOH had the least mean value (21.71 ± 1.21 mg/kg). The nickel content in the soils were in the order: dumpsite (35.93 ± 1.63 mg/kg) > cultivated soils (27.89 ± 1.69 mg/kg) > fallow soils (27.24 ± 0.93 mg/kg) > forest soils (23.79 ± 0.98 mg/kg). Although, dumpsite soils had the highest nickel content, it was below the maximum allowable concentration of 50 mg/kg Ni. The results indicated that available nickel ranged from 15.62 to 43.80 mg/kg in all the soil of the four land use types. EDTA is therefore recommended for Ni extraction in agricultural soils. While care should be taken when using old dumpsite soil for planting since the level of Ni could be high in such soil.
Keywords:
assessment
southwest
selected
nigeria
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