Evaluation of Universal Extractants for Determination of Selected Micronutrients on Soils Developed over Charnockite in Ekiti State

摘要

Twenty six pedogenic soils developed on charnockite were used to evaluate the suitability of extractants for bioavailability of manganese, copper, zinc and iron in the soils to plants. These micronutrients cation were extracted from the soils using five different extractants, namely, Neutral Normal NH 4 OAc, NH 4 OAc buffered with glacial acetic acid to pH 4.8, 0.1 M HCl, 0.05 M HCl + 0.025 M H 2 SO 4 , 0.05 M EDTA + 0.1 M (NH 4 ) 2 CO 3 . The contents of extractable Mn, Cu and Fe ranged were 0.04-1.50, 0.39-9.01 and 14.10-639.90 mg kg -1 respectively with Mehlich 1 having the highest mean values of 0.83, 5.45 and 341.46 mg kg -1 across the locations. EDTA was more efficient in the extraction of the available Zn having a mean value of 0.11 mg kg -1 and varied from 0.01-0.22 mg kg -1 in all the soils. The 0.1 M HCl was moderately efficient in the micronutrients cation assessment, but the NH 4 OAc extractants were generally less effective in assessing the micronutrients cation even though the buffered solution gave a better extractability over the neutral normal solution. All the extractants were significantly correlated (p 0.05 M EDTA + 0.1 M (NH 4 ) 2 CO 3 > 0.1M HCl > NH 4 OAc pH 4.8 > NH 4 OAc pH 7.0.