Abi M. Taddesse

Evaluation of Universal Extractants for Determination of Some Macronutrients from Soil

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.

Determination of the levels of selected metals in seeds, flowers and fruits of medicinal plants used for tapeworm treatment in Ethiopia

The level of accumulation of selected essential and non-essential metals, namely; Ca, Cu, Fe, Zn, Mn, Cd, Pb, and Cr have been investigated in the seeds, fruits, and flowers of some medicinal plants utilized for tapeworm treatment in Ethiopia and their respective soil samples. These include seed of Cucurbita maxima (Duba), fruit of Embelia abyssinica (Ankoko), flowers of Hagenia abyssinica (Kosso), and fruits of Rosa abyssinica (Kega) and their respective soil samples. A wet digestion procedure with a mixture of conc. HNO3 and HClO4 for the plant samples and a mixture of conc. HNO3, HCl, and H2O2 for soil samples were used to solubilize the metals. Ca (1280–12,670 mg kg−1) was the predominant metal followed by Fe (104–420 mg kg−1), and Zn (18–185 mg kg−1) in all the plant materials except for Hagenia abyssinica flower from Hirna in which Mn (16–42 mg kg−1) followed by Fe. Among the non-essential toxic metals, Pb was not detected in Cucurbita maxima of Boji, Gedo and Hirna origins and in Rosa abyssinica of Hirna site. Similarly, Cr was not detected in Rosa abyssinica fruits of Boji and Gedo sites. The sampled soils were found to be between strongly acidic to weakly basic (pH: 4.7–7.1). In the soil samples, Ca (8528–18,900 mg kg−1) was the most abundant metal followed by Fe (417–912 mg kg−1), Zn (155–588 mg kg−1), Mn (54–220 mg kg−1), Cr (21–105. mg kg−1), Cu (11–58 mg kg−1), Pb (13–32 mg kg−1) and Cd (2.8–4.8 mg kg−1). The levels of most of the metals determined in the medicinal plants and the respective soil samples are in good agreement with those reported in the literature and the standards set for the soil by various legislative authorities.

Levels of essential and non-essential metals in edible mushrooms cultivated in Haramaya, Ethiopia

BackgroundFruiting bodies of two oyster mushroom (Pleurotus ostreatus and Pleurotus florida) species and their respective substrate samples cultivated and collected from the Mushroom Research, Production and Training Laboratory of the Haramaya University, Ethiopia, were analyzed for essential and non-essential metals, viz., Cu, Fe, Zn, Mn, Cd and Pb contents by flame atomic absorption spectrometry after digestion employing dry, wet and microwave digestion techniques. Concentrations of the analyzed metals were expressed on a dry weight basis (mg/kg).ResultsThe mean metal concentration (mg/kg in dry weight) in the mushroom and respective substrate samples, respectively; for Pleurotus ostreatus were: Cu (51.19, 48.97), Fe (220.87, 299.51), Zn (89.68, 62.55) and Mn (47.55, 58.32). The mean metal concentration (mg/kg in dry weight) in mushroom and the respective substrate samples, respectively, for Pleurotus florida were: Cu (53.56, 51.87), Fe (243.92, 265.23), Zn (95.26, 64.25) and Mn (41.29, 62.55). However, Cd and Pb was not detected in both mushroom and substrate samples. The bio-accumulation factor of the heavy metals was calculated and a highest accumulation of Cu and Zn from substrate was observed for all the analyzed mushrooms samples. The observed results were also compared with the reported results.ConclusionsIn this study, the highest concentrations of Cu, Fe, Zn and Mn were confirmed. These elements generally are essential for humans, and may not possibly cause health problems even if mushrooms are consumed regularly. Furthermore, the quantities of the metals found in the samples were within the limits recommended by international organizations like the WHO/FAO Expert Committee on Food Additives. On the other hand, the amounts of Cd and Pb were found to be very low. These elements are toxic to humans, especially at higher doses; however, the concentrations of these non-essential metals were below detectable limit.

Effect of Citrate Concentration on the Extraction Efficiency of Selected Micronutrients from Soil

ABSTRACT This study was carried out with the objective of evaluating the effect of citrate concentration on the extraction efficiency of some micronutrients from soil. Composite surface soil samples (0–20 cm) were collected from Eastern Harage Zone (Babile and Haramaya Districts), Wolaita Zone (Damot Sore, Boloso Bombe, Damot Pulasa and Humbo Districts) and Dire Dawa Administrative Council in purposive sampling. The treatments were arranged in completely randomized design (CRD) with three replications. A greenhouse pot experiment with soybean plant was conducted to determine the correlation between soil test methods and the selected micronutrients, such as iron (Fe), copper (Cu), manganese (Mn) and zinc (Zn) in the leaves of the plant. The results showed that, among the different citrate concentrations with strontium chloride (SrCl2) tested for the determination of available Fe, Mn and Zn, the highest correlation coefficients (r = 0.82, p < 0.05), (r = 0.96, p < 0.001) and (r = 0.98, p < 0.001) were found between the diethylenetriamine pentaacetic acid (DTPA) method and 0.02 M strontium chloride (SrCl2)-0.025 M citric acid extractant, respectively. Therefore, 0.02 M SrCl2-0.025 M citric acid extractant is considered to be the most effective for the determination of Fe, Mn and Zn in soils of the studied areas. Similarly, high correlation coefficients (r = 0.97, p < 0.001) were found between DTPA and 0.02 M SrCl2-0.05 M citric acid and (r = 0.88, p < 0.01) between DTPA and 0.02 M SrCl2-0.025 M citric acid extractants for the determination of available Cu from soils. Hence, the 0.02 M SrCl2-0.05 M citric acid extractant was shown to be the best for the determination of Cu in soils of the studied areas. However, considering the use of universal extractant, the 0.02 M SrCl2-0.025 M citric acid extractant could easily be adopted as a procedure for the determination of Fe, Cu, Mn and Zn for both agricultural and environmental purposes. The greenhouse experiment confirmed the result.