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Abstract
Evaluation of nutrient status in soil is important for nutritional, environmental, and economical aspects. The objective of this work was to find out the most suitable universal extractant for determination of available phosphorus (P) and nitrate (NO3-) and exchangeable potassium (K), calcium (Ca), and magnesium (Mg) from soils using 0.01 M calcium chloride (CaCl2), 0.01 M barium chloride (BaCl2), 0.1 M BaCl2, 0.02 M strontium chloride (SrCl2), Mehlich 3, and ammonium bicarbonate diethylene triamine penta acetic acid (AB-DTPA) extractants. Composite surface soil samples (0–20 cm) were collected from the Eastern Harage 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 experiment was carried out in a completely randomized design (CRD) with three replications. Results indicated that the greatest correlations were found between Mehlich 3 and Olsen method and also between 0.02 M SrCl2 and Olsen method for available P. The amount of NO3– extracted by 0.02 M SrCl2 was significantly correlated to the amount determined by 0.5 M potassium sulfate (K2SO4). The amounts of exchangeable K, Ca, and Mg determined by ammonium acetate (NH4OAc) method were significantly correlated to the amount determined by universal extractants tested. In general, both 0.02 M SrCl2 and Mehlich 3 can serve as universal extractants for the macronutrients considered in this study with the former being more economical when NO3– is included.
Acknowledgments
We acknowledge the staff members of Soil Chemistry Laboratory, Haramaya University, and staff members of Ethiopian Geological Survey, Addis Ababa, for providing us with the necessary support to conduct this study.