CHEMICAL COMPOSITION OF THE GREEN BIOMASS OF INDIGENOUS TREES AND SHRUBS IN THE HIGHLANDS OF CENTRAL ETHIOPIA: IMPLICATIONS FOR SOIL FERTILITY MANAGEMENT

The use of green biomass of indigenous trees and shrubs to supply nutrients to agricultural crops is a traditional practice in the highlands of Central Ethiopia. A study was carried out from 2004 till 2006 to characterize the quality of the green biomass of indigenous trees and shrubs based on the content of water, macronutrients, lignin and soluble phenolics. The tree and shrub species studied were Senecio gigas, Hagenia abyssinica, Dombeya torrida, Buddleja polystachya and Chamaecytisus palmensis. The first four are indigenous species, while the last is an exotic species. The water content of the foliage in S. gigas was the highest. The N content of the foliage of the indigenous species was comparable with C. palmensis. The highest K content was found in the foliage, flower bud and stem of S. gigas. The lignin content in the foliage and flower bud of H. abyssinica was the lowest. Based on the N content, lignin and soluble phenolics, indigenous species had intermediate to high quality, whereas exotic species had high quality green biomass for managing soil fertility.