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Accueil du site → Doctorat → Suède → Tree species diversity, topsoil conditions and arbuscular mycorrhizal association in the Sidama traditional agroforestry land use, Southern Ethiopia

SVERIGES LANTBRUKS UNIVERSITET (2003)

Tree species diversity, topsoil conditions and arbuscular mycorrhizal association in the Sidama traditional agroforestry land use, Southern Ethiopia

Asfaw, Zebene

Titre : Tree species diversity, topsoil conditions and arbuscular mycorrhizal association in the Sidama traditional agroforestry land use, Southern Ethiopia

Auteur : Asfaw, Zebene

Université de Soutenance : SVERIGES LANTBRUKS UNIVERSITET (SWEDEN)

Grade : Fildr 2003

Résumé
Sidama farmers cultivate trees to meet their food, wood, fodder and other service needs. Tree cultivation intensity has increased during the past three decades. Significant positive correlation was found between farm size and number of species, and number of stems per farm. The number of tree species per farm averaged 16 and ranged from 4 to 28. Within farms, about ten different field types were identified of which enset fields contain the highest number of species. Wealthy households have more tree species than poor households. In general the largest number of tree species, the largest number of stems and the largest basal area ha⁻¹ were recorded on farms of wealthy households. Based on farmers´knowledge and laboratory studies, nutrient accumulation in the topsoil under Cordia africana, Millettia ferruginea and Eucalyptus camaldulensis managed under three agroforestry practices (AF) on different farms at three sites was evaluated. Significantly higher concentration of P was observed under Millettia and Cordia than under Eucalyptus. pH under Millettia and Cordia were significantly higher than under Eucalyptus at one site. Topsoil under Millettia and Cordia also had significantly higher levels of exchangeable Ca and Mg than Eucalyptus. For scattered AF soil and enset, plants were sampled at laterally increasing distances from the tree trunks and outside the canopy on enset and maize fields. Under canopies of both Cordia and Millettia trees, the diameter of enset was significantly greater than that of enset plants grown in open fields. Topsoil under canopies of scattered Cordia and Millettia trees, compared with open fields, generally had higher pH, CEC, increased total N, organic C and available P, but had no effect on some exchangeable bases. Six tree-crop combinations and two open-maize plots in enset and maize fields were selected to study the level of indigenous arbuscular mycorrhizal (AM), number of spores and levels of root colonization. At field level, tree-crop combinations induced a higher number of spores and level of colonization than in an open-maize field. The proportions of roots were in the following order : tree-enset-coffee > tree-enset > tree-maize for Cordia trees and tree-enset > tree-enset-coffee > tree-maize for Millettia trees. Beneath both Cordia and Millettia trees scattered on maize fields, the proportion of colonized root decreased with increasing distances laterally from the tree trunks. At nursery level, significantly higher levels of root colonization were observed for maize plants grown on soil from beneath tree enset-coffee and enset plots than those grown on soil from tree-maize and open-maize plots. The percentage of AM colonized roots of maize was significantly positively correlated with the number of spore counts for field soils.

Mots clés : cordia, eucalyptus camaldulensis, millettia, planting, socioeconomic environment, top soil, nutrients, mycorrhizae, colonizing ability, roots, spores, ensete, maize, agroforestry, ethiopia

Présentation

Page publiée le 12 février 2004, mise à jour le 17 juin 2017