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Die Wirksamkeit von Boden

Die Wirksamkeit von Boden

Performance of farmland

Performance of farmland terraces in maintaining crop productivity 6 PERFORMANCE OF FARMLAND TERRACES IN MAINTAINING CROP PRODUCTIVITY 6.1 Introduction Various measures have been taken by the Ethiopian government to circumvent the problem of low agricultural productivity due to high erosion and poor soil fertility. The measures include agricultural extension services focusing on utilization of agricultural inputs such as chemical fertilizer and improved seed (Belay and Abebaw 2004), and promotion of soil and water conservation (SWC) (Amsalu and de Graaff 2007; Nyssen et al. 2007; Bingxin et al. 2010). However, the intervention programs are challenged by different factors. For instance, the extension programs are unlikely to succeed in an environment where fertilizer use is much below the soil nutrient lost through crop harvest and soil erosion (Bingxin et al. 2010). The SWC program is mainly constrained by limited adoption and continuity issues (Amsalu and de Graaff 2007). SWC intervention has been widely implemented in the northern highlands, which cover large areas (Herweg and Ludi 1999; Amsalu and de Graaff 2007). Among the different SWC interventions, contour terracing has been widely implemented on farmlands. However, there are different opinions concerning the advantages of farmland terracing. Farmland terracing has been known to modify terrain by reducing slope angle and length at farm level and changing slope shape at the micro-watershed level, thereby decreasing soil erosion, and enhancing hydrology and crop productivity (Shiferaw and Holden 1999; Badege 2001; Sonneveld and Keyzer 2003; Nyssen et al. 2007). In contrast, some researchers and farmers have criticized terracing for its negative effects such as yield and fertility gradients within a terrace, for harboring rodents thus resulting in crop yield loss, for reducing farm size, and for creating problems for oxen-drawn plowing (Herweg and Ludi 1999; Dercon et al. 2003; Vancampenhout et al. 2006; Amsalu and de Graaff 2007; Nyssen et al. 2007). The aim of this chapter is to provide a quantitative analysis of the impact of farmland terracing in improving and/or maintaining crop yields, and to evaluate terrace performance across terrace age, within a terrace and across the terrain. The results will provide empirical evidence concerning the performance of farmland terracing with respect to crop production and productivity. 84

Performance of farmland terraces in maintaining crop productivity 6.2 Material and methods 6.2.1 Study area The study was conducted in the Maybar soil conservation research site (MSCRS), which is located in the Lake Maybar watershed in the sub-humid agro-ecological zone, locally classified as Dega (Hurni 1998). Dega agro-ecology is characterized by cool, humid highland conditions at altitudes between 2500 and 3200 m a.s.l. (NMSA 1996; Hurni 1998). The area receives bimodal rainfall namely Belg and Kiremt (NMSA 1996; Hurni 1998; SCRP 2000). The Belg (spring) is a first rainy season between April and May, while Kiremt (main) is the second rainy season between July and September. Due to the bimodal rainfall, the area has two cropping seasons (Herweg and Ludi 1999). However, in some cases there is only one cropping season when the Belg rainfall fails. The main crops are cereals and pulses and include wheat (Triticum spp), emmer wheat (Triticum spp), horse bean (Vicia faba), field pea (Pisum sativum), barley (Hordeum spp), maize (Zea mays) and teff (Eragrostis tef) (SCRP 2000). For further details of the study area see Chapter 5. 6.2.2 Plot selection and sampling Crop yield data were obtained from the project coordination office in Addis Ababa after official communication with the Sirinka Research Center and Amhara Regional Agricultural Research Institute (ARARI). Grain and biomass (straw and grain cover) yield data collected by MSCRS were used in this analysis. In the establishment phase, the project collected baseline data, constructed SWC structures and established different setups such as field plots, test plots, and meteorological and river gauge stations. The baseline data are based on soil surveys while an appraisal was conducted for the land degradation status. The field plots were established for runoff and erosion monitoring, soil conservation experiments and crop yield monitoring (Herweg and Ludi 1999; SCRP 2000). The project identified 40 fixed plots (Figure 6.1) to monitor the yields of major crops. The analysis in this study is based on the yield data of the fixed plots. Terracing was made possible by the technical and financial support of the program (SCRP), whereas cultivation is based on farmers’ traditional practices that involve oxen-drawn cultivation, hand weeding and no or very limited fertilizer application (Herweg and Ludi 1999; SCRP 2000). Crop selection and management were 85