TREE SPECIES SCREENED ON NITOSOLS OF CENTRAL ETHIOPIA: BIOMASS PRODUCTION, NUTRIENT CONTENTS AND EFFECT ON SOIL NITROGEN

Abstract

KINDU, M., GLATZEL, G., TADESSE, Y. & YOSEF, A. 2006. Tree species screened on Nitosols of Central
Ethiopia: biomass production, nutrient contents and effect on soil nitrogen. Shortage of tree biomass is a
severe problem in the highlands of Ethiopia. A screening trial was conducted from 1997 till 2002 to select
fast growing and high biomass producing tree species, evaluate foliage and wood macronutrient contents
of different tree species, and assess effect of tree species on soil nitrogen beneath their canopies. Seven tree
species: (i) Acacia decurrens, (ii) Chamaecytisus palmensis, (iii) C. proliferus, (iv) Eucalyptus globulus, (v) E.
camaldulensis, (vi) Grevillea robusta and (vii) Hagenia abyssinica were evaluated in a randomized complete
block design with three replications. All species were exotic except H. abyssinica. Grevillea robusta exhibited
slow height growth and wood production as compared with the five exotic species. Acacia decurrens provided
the highest mean dry biomass at 64 months. Foliar N levels in A. decurrens, C. palmensis and C. ploriferus were
significantly higher than those in the other four tree species. Acacia decurrens, C. palmensis and C. ploriferus
are N-fixing tree species. Hagenia abyssinica had higher K levels in the foliage and wood. Eucalyptus species
tended to deplete soil fertility whereas C. palmensis and C. ploriferus improved soil fertility. Chamaecytisus
species and A. decurrens can be short-term options for soil fertility improvement and a source of fuelwood
respectively.