Analysis of the Mineral Content of Wood Ashes of Selected Plants Used for Soil Amendments in Eritrea

Abstract

Wood ash  contains  all  the  components  of  wood  in  a  concentrated  form,  except  for  carbon, hydrogen and nitrogen which evaporate during the burning of wood. The mineral concentration of the ashes from seven selected trees namely Acacia seyal, Acacia etbaica, Acacia albida, Acacia tortilis, Leucaena leucocephala, Olea europea, Musa sapientum found in Eritrea was studied. Most of the trees are commonly used for household fire in the rural and urban communities of Eritrea. The purpose of this study was to assess the levels of minerals and thus determine the application of the ashes of the selected trees for soil amendment. Moderately sized tree branches were ashed in a furnace at 600ºC for 6 hours and the resulting ash was homogenized, filtered and digested. Aqua-regia was used to digest the ash samples and ICP-OES was employed to analyse the levels of the elements. Based on the analysis, the digestion method was found to be effective in recovery of minerals from the wood ashes. The percentage of ashes produced from the trees, except Musa sapientum, ranged from 0.88 up to 4.66. The results of the study revealed that the ashes of the selected plants contained various concentrations of the minerals vital for soil enrichments. The major elements found in the wood ashes include Ca, K, Mg, P, S, Fe and Na. The level of the major elements in this report was consistent with previously published reports. Moreover, the concentration of heavy metals in the studied plant ashes was below the permissible limits and therefore the ashes can be employed as liming agents and sources of important nutrients in soil enrichment. This is a very first report related to the levels of minerals in wood ashes in the country and thus can be used as reference for further detailed studies.