Evaluation of universal extractants for determination of selected micronutrients from soil
A study was carried out with the objective of identifying the most suitable universal extractant for determination of selected micronutrients from soils. Composite surface soil samples (0-20 cm) were collected from Eastern Harargie Zone (Babile and Haramaya Districts), Wolaita Zone (Damot Sore, Boloso Bombe, Damot Pulasa and Humbo Districts) and Dire Dawa Administrative Council by purposive sampling. The treatments were arranged in completely randomized design (CRD) with three replications at Haramaya University Soil Laboratory. The results showed that among the universal extractants examined for the determination of available Fe, Cu and Zn, the highest correlation coefficients (r = 0.95), (r = 0.99) and (r = 0.97) at (p < 0.001) were found between DTPA and AB-DTPA for available Fe, Cu and Zn, respectively. Therefore, AB-DTPA universal extractant can easily be adopted as a soil testing method for the determination of available Fe, Cu and Zn in some selected soils of Ethiopia. Similarly, the concentration of available Mn determined by DTPA method was significantly correlated with the amount determined by tested universal extractants. The highest correlation coefficients were found between DTPA and 0.01 M CaCl2 (r = 0.90), DTPA and 0.01 M BaCl2 (r = 0.87), DTPA and 0.02 M SrCl2 (r = 0.86), DTPA and 0.1 M BaCl2 (r = 0.89) and DTPA and AB-DTPA (r = 0.85). However, considering the use of universal extractant, AB-DTPA could be the most suitable universal extractant for the determination of available Mn in soils of the studied areas as well. Therefore, AB-DTPA extractant is considered to be superior and the most suitable universal extractant for determination of available Fe, Cu, Mn and Zn in soil of the studied areas.
KEY WORDS: Micronutrients, Multinutrient extractant, Soil testing method, Unbuffered salts
Bull. Chem. Soc. Ethiop. 2015, 29(2), 199-213.