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

Abstract

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.