| Abstract: |
| The ancient and widespread use of tree and bush fallows to recuperate soil productivity following several years of cropping, has resulted in research aimed at identifying, planting and managing trees for soil improvement. The goal is either to reduce the traditional fallow periods (normally between 4 and 25 years) or to eliminate the fallow priod by introducing systems in which "soil-improving" trees are managed together with crops or pasture species (agroforestry). Trees commonly used by farmers for soil improvement include Acioa barteri, Calliandra calothyrsus, Erythrina berteroana, Prosopis cineria, Samanea saman and Sesbania sesban. Although many of these species are largerly undomesticated, a number of them are currently the focus of genetic improvement programmes. The possibility exists that in such programmes selections could be made for tree characteristics to significantly improve soils. A synthesis of the research data from work on acid and high base status soils in the humid, sub-humid, and semi-arid regions of central and Latin America, Africa, and Asia is used to critically evaluate "tree soil improvement" hypotheses are discussed in the context of developing domestication strategy for multipurpose species, taking account pf the influence of the species on the environment. |
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