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Die Wirksamkeit von Boden

Die Wirksamkeit von Boden

Literature review

Literature review harvest (grain and residue), the traditional practices that used to maintain soil fertility have almost been completely abandoned (Omiti et al. 1999; Bingxin et al. 2010; Spielman et al. 2011). Traditionally, farmers practice fallowing and apply animal manure that allows fertility restoration. However, due to the population pressure and increasing demand for food and shortage of fuel wood that led to use of animal dung for household energy, and the fallowing practice has been nearly abandoned, which in turn has triggered soil fertility decline and crop productivity loss (Omiti et al. 1999; Haileslassie et al. 2005; Spielman et al. 2011). Land holdings are also reduced due to frequent redistribution. The per capita land area holding fell from 0.5 ha in the 1960s to 0.2 ha by 2008 (Spielman et al. 2011). Crop production depends on rainfall, but rainfall is erratic in the country. The late start and early stop of rain considerably impacts crop and livestock production and productivity (Tadesse 2001; Tilahun 2006; Descheemaeker et al. 2010). Similarly, livestock production and productivity are limited by poor management, storage systems, and animal health services, and by feed problems (Belay and Abebaw 2004; Descheemaeker et al. 2010). Livestock feed is a critical problem and substantially depends on crop residues (Haileslassie et al. 2005). Particularly the recurring droughts threaten the livestock sector, as animals face feed and water shortages during these dry periods (Belay and Abebaw 2004; Descheemaeker et al. 2010). Although in croplivestock farming systems, the two sectors complement each other and they also negatively influence each other (Haileslassie et al. 2005). The limited cultivable and grazing lands have resulted in competition between the two sectors. As a result, cultivation and grazing expanded into forest and marginal lands, which aggravated the land degradation processes (Bojö and Cassells 1995; Badege 2001). The above facts illustrate that agricultural production suffers from various constraints. These result in low agricultural production and productivity that triggers inappropriate resource utilization and increases land degradation. 2.4 Land degradation and its implications Land degradation is defined differently by different authors. Some regard it as a synonym of soil degradation (Stocking and Murnaghan 2000), while others explain the difficulty to define it because of its wider range and scope (Barrow 1991). According to 10

Literature review the United Nations Convention to Combat Desertification (UNCCD), land degradation is defined as a natural process or a human activity that causes the land to be unable to provide intended services for an extended time (FAO, 2004). The history of land degradation is as old as the human civilization, and has resulted in irreversible impacts in some cases. For example, the Atacama Desert once was a dense jungle (Kelley 1983). At a global scale, agricultural land lost due to degradation is estimated at about 40% out of which agricultural land in developing countries accounts for the larger portion (FAO, 2004). Developing countries, especially in SSA, have been losing large tracts of land due to this problem (Nana-Sinkam 1995; Scherr 2000; Vlek et al. 2008). Although there are no well documented or detailed studies concerning land degradation in Africa at the continental level, the few studies conducted at the exploratory level indicate the severity of the problem (Nana-Sinkam 1995; Vlek et al. 2008). Nana-Sinkam (1995) reported that whenever one has the opportunity to travel across various parts of SSA countries, it is easy to see that most inhabited parts are affected by the problem. A study of the FAO also indicated that out of the total land of Africa, 47% is too dry for rainfed agriculture and only 16% of the land has no serious fertility limitation, while the remaining 37% is affected by land degradation (FAO, 2004). The limited agricultural land on the continent has been shrinking due to land degradation. The rate in Africa is estimated at about 230 million ha annually (FAO 2004). A satellite-data-based study also showed that SSA countries that are supposed to have agricultural potential are losing enormous areas of productive land due to the problem (Vlek et al. 2008). As in the other SSA countries, the problem is crucial in Ethiopia (Hurni 1993; Dubale 2001; Nyssen et al. 2004). Land degradation started as early as the human history of animal domestication and control over fire (Lambin et al. 2003). Human activities have resulted in intended and unintended consequences for the environment. Anthropogenic forest fire was practiced during animal hunting in the earlier ages, and forest clearance for agriculture since recent times. These activities have resulted in a considerable impact on the environment beyond the intended extent and depth (Hurni, 1987; Lambin et al. 2003). The causes of land degradation are complex. Nevertheless, they are similar in many developing countries. Population pressure has been the major driver of the problem (Nana-Sinkam 1995; Tekle 1999; Scherr 2000), and has resulted in extensive 11

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