A Review Paper on: The Role of Agroforestry for Rehabilitation of Degraded Soil

Abstract

The world population growth is steadily increasing and the situation is even more alarming in developing countries /third world continents.  For instances, Ethiopia is characterized by a great bio-physical diversity, dividing the country in several agro-ecological zones, each with a specific fauna and flora. It therefore is an important centre of biodiversity and endemism (Zewge and Healey 2001). Due to the out going population (76 million) growth of Ethiopia (CSA 2008) and overgrazing and deforestation for agricultural activities, fuel wood and construction material, overall natural forest cover had decreased to a level of 2.5 percent of which only one twelfth has a dense forest structure (Zewge and Healey 2001). The combination of high endemism and fast habitat degradation in Ethiopia leads to a great risk of species extinction (Zewge and Healey 2001).

Poverty and natural resources/environmental degradation tend to negatively reinforce each other; that is, as the land is degraded, agricultural productivity is lowered, resulting in decreasing incomes and food security and vise versa (Eyasu 2002, Selamyehun 2004; Wakeneand Heluf2000). This has resulted in migration of rural poor to urban centers; increased cultivation of marginal lands; encroachment into forest regions; and depletion of land resource base of small holders (Demelet al., 2000). Moreover, the country’s topographic nature has made it more liable to degradation (Girma 2000). To overcome this problem, agroorestry has been proposed as one of the options for its positive influences on soil fertility, mainly due to tree components (Kamara and Haque 1992; Campbell et al., 1994). The inclusion of compatible and desirable species of trees/woody perennials in agroforestry can result in marked improvement in soil fertility by: (i) increasing organic matter content of soil through addition of leaf and roots litter as well as other plant parts (Young 1997; Rao et al., 1998), improving organic matter status, which can in turn result in increased activity of micro-organisms in the root zone (Khanna 1998; Young 1997), (ii) enhancing efficient nutrient cycling within the systems (Khanna 1998), and (iii) controlling soil erosion (Young 1997; Rao et al., 1998).

The objective of this seminar is to review the role of AF towards cease soil degradation.