5 years ago

Die Wirksamkeit von Boden

Die Wirksamkeit von Boden

Performance of farmland

Performance of farmland terraces in soil fertility maintenance Figure 5.1 Location of study area: (a) Wello in Ethiopia, (b) Maybar watershed in Wello, and (c) Sampling points in Maybar watershed 5.2.2 Sampling site selection and design A reconnaissance survey was conducted in the north and south Wello zones to identify appropriate sites. The criteria were availability of different-aged farmland terraces in different landscape positions. SWC measures such as terracing have been implemented over large areas at a time through mass community mobilizations. As a result, it was difficult to find terraces of different ages, particularly non-terraced farmland (control) in one or similar watersheds. Moreover, terrace maintenance was based on individual interests, which meant differences on terraces that had however been constructed at the same time in a watershed. Thus, it was decided to conduct the research in the MSCRS, where soil data were available for the time before SWC interventions, and the terraces had been constructed and maintained over a similar period of time. The soil data were used as control to track the changes after the terracing. The Lake Maybar watershed was classified into different slope categories using a digital elevation model (DEM). The DEM output (Figure 5.2), topographic maps (1:50,000 scale), aerial photograph (1:50,000 scale) and the watershed soil map 62

Performance of farmland terraces in soil fertility maintenance were used to classify the study area to identify sampling plots. Accordingly, the study site was classified by adopting the FAO system (FAO 2006) of classification into flat to very gently sloping (< 3%), gently sloping (3 - 5%), sloping (5 - 8%), strongly sloping (8 - 15%), moderately steep (15 - 30%) and steep to extremely steep (> 30%). On the MSCRS, experiments are being conducted on 40 fixed plots on slope below 30%. Farmland terraces were constructed, and yields and agronomic practices have been monitored for the last two decades on fixed plots (see Chapter 6). Terracing was deliberately omitted on the land with less than 3% slope because of little erosion on this slope (Hurni 1988). Based on slope, the plots were grouped into four categories, i.e., 3 - 5%, 5 - 8%, 8 - 15% and 15 - 30%. Accordingly, 16 plots representing 4 plots from each slope category were identified. Out of the profile pits of the 1983 soil survey, those on the fixed plot were selected. Figure 5.2 Slope map of Lake Maybar watershed Three sampling positions (Figure 5.3) on the terraces of the fixed plots were selected, i.e., low-terrace (A), mid-terrace (B) and up-terrace (C). The location of the 63

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