Levels of Selected Essential and Non-Essential Metals in the Soil and Ginger (<i>Zingiber officinale</i>) Cultivated in Wolaita Zone, Ethiopia

Ginger (Zingiber officinale) is an important spice and medicinal plant used in different parts of the world. The objective of current study was to determine the level of essential and non-essential metals in ginger and its correlation with concentration of metals in the supporting soil. The level of K, Na, Ca, Mg, Mn, Fe, Zn, Cu, Co, Cd and Pb in soil and ginger cultivated in the selected districts of Wolaita zone, Southern Ethiopia were determined using flame atomic absorption spectrometry. A 0.5 g ginger sample was digested using a mixture of 4 ml HNO3 and 1.5 ml HClO4 at 210°C for 150 minutes, and a 0.5 g soil sample was digested employing a mixture of 6 ml aqua-regia and 1 ml H2O2 at 280°C for 150 minutes. The metal concentrations range in dry weight basis for ginger samples is decreasing in the order: K (1691 - 3487 mg/kg) > Mg (701 - 1583 mg/kg) > Ca (862 - 1476 mg/kg) > Na (398 - 776 mg/kg) > Mn (325 - 672 mg/kg) > Fe (6.14 - 11.92 mg/kg) > Zn (5.30 - 10.09 mg/kg) > (0.12 - 0.23 mg/kg) for Pb. The concentration of Cd, Cu and Co in ginger samples were below the limit of detection. The results revealed that ginger has the ability to accumulate relatively higher amounts of K and Mg among the determined essential metals. The soil samples have been found to be acidic pH, sandy clay loam in texture, a very low electrical conductivity and moderate level of (CEC, organic carbon, available phosphorus and total nitrogen). Although, a positive correlation between the levels of K, Mg, Zn, Mn in ginger and soil samples were observed. All the non-essential metals analyzed in this study were below the permissible ranges set by FAO/WHO.

Determination of Selected Essential and Non-Essential Metals in Three Types of Teff (<i>Eragrostis tef</i>) Cultivated in Southern Ethiopia

Teff (Eragrostis tef) is used to supply staple food “injera” for many Ethiopians. The present study was aimed toward determining the extent of selected metals that can exist in three types of teff cultivated in selected districts of southern Ethiopia. The level of those metals was determined by flame atomic absorption spectrometry. The optimized wet digestion procedure was evaluated employing a spiking method and an acceptable percentage recovery of (91.1% - 108.9%) has been obtained for metals in the teff. Oven dried 1 g of teff samples were digested using 5 mL of HNO3 and 1 mL of HClO4 at 300°C for 3 hours. The result indicated that the mean concentration of metals (in mg/kg dry weight basis) in teff samples were found to be from 1206.9 to 1768.9 of Ca, 2463.9 to 2554.7 of Mg, 82.6 to 109.9 of Na, 2879 to 3075 of K, 207.4 to 239.5 of Fe, 55.9 to 100.4 of Mn, 27.1 to 87.1 of Zn, 5.4 to 45.5 of Cu and 0.118 to 0.130 of Pb respectively. However, Cd is below the method detection limit. A statistical analysis of variance revealed that there was a significant difference (p ≤ 0.05) between the mineral content in three teff types and teff from the three districts. Red teff had higher essential metal contents except Cu followed by brown teff. Strong positive correlation was recognized between Mg with Ca and K, the rest have moderate or weak correlation. Further study has been done on the mineral contents of similar variety or three types of teff with the soil analysis from different locations.

Determination of Selected Metals and Nutritional Compositions of Pigeon Pea (<i>Cajanus cajan</i>) Cultivated in Wolaita Zone, Ethiopia

This study was aimed to determine the level of selected metals and nutritional composition of pigeon pea seed collected from seven districts of Wolaita zone. A wet digestion procedure involving the use of mixtures of (69% - 72%) HNO3 and (70%) HClO4 at an optimum temperature and time duration was used to determine metals by using flame atomic absorption spectrometry. Kjeldahl digestion method, Soxhlet extraction and furnace were used to determine nutritional values of pigeon pea, and physicochemical properties of soils were assessed using standard methods. The results showed that the levels of concentration of metals in mg/kg dry weight were ranged 105.17 to 144.07 for K, 8.95 to 12.67 for Mg, 7.74 to 12.27 for Ca, 0.247 to 0.543 for Fe, 0.122 to 0.313 for Zn, 0.061 to 0.432 for Mn, 0.087 to 0.134 for Cu and 0.0011 to 0.00196 for Cr. The proximate composition of pigeon pea was in the range of 19.28% to 25.79% for crude protein, 0.993% to 1.75% for crude fat, 3.75% to 5.31% for ash, 10.65% to 13.73% for moisture, 2.28% to 3.06% for fiber, 54.36% to 60.1% for carbohydrate and 326.8 to 345.23 Kcal for energy. The pH of the soil was in the range from pH 5.09 (strongly acidic) to 6.77 (slightly acidic), EC of the soil ranged from 0.047 to 0.14 dS/m (low), the soil OC level was from 1.6% to 2.42% (moderate), total Nitrogen was from 0.12% to 0.23% (low to moderate), the available Phosphorus content of the soil was from 6.82 to 13.52 mg/kg (low to moderate), CEC value of the soil was from 14.8 to 23.53 meq/100g (moderate). The textural classes of soil were sandy clay loam for all sites except Abela abaya. The study confirmed that pigeon pea was a good source of proteins, carbohydrates, and selected metals such as Mg, K, Ca, Fe, Zn, Mn, Cu, and Cr. The concentration of metals and nutritional compositions of pigeon pea seed were found at a permissible level.

Integrated soil, water and agronomic management effects on crop productivity and selected soil properties in Western Ethiopia

Land degradation is a major challenge limiting crop production in Ethiopia. Integrated soil and water conservation is widely applied as a means to reverse the trend and increase productivity. This study investigated the effects of such integrated approaches at two sites, Jeldu and Diga, inWestern Ethiopia. A split plot design with physical soil and water conservation in the main plots and agronomic practices in the sub plots was employed. Maize (Zea mays L.) followed by groundnut (Arachis hypogaea L.) at Diga, and wheat (Triticum aestivum) followed by faba bean (Vicia faba L.) were the test crops. Surface soils were sampled before sowing and after the crop harvest, and analyzed for selected parameters. Soil moisture content during the growing period was also monitored. The use of soil bund increased soil moisture content, and significantly (P < 0.05) increased days to flowering and maturity, kernel weight and harvest index, grain yield of the test crops, with the exception of maize. The improved agronomic practices (intercropping, fertilization and row planting) significantly (P < 0.05) increased grain yield of all the test crops. The effect of the treatments on soil parameters may require longer time to be evident. Although the increase in crop yield due to soil bund and the improved agronomic practices is eminent, economic analysis is necessary before recommending the widespread use of the improved options.