5 years ago

Die Wirksamkeit von Boden

Die Wirksamkeit von Boden

Performance of farmland

Performance of farmland terraces in soil fertility maintenance sampling points was as follows: A) low-terrace position refers to the location 50 cm from the lower terrace riser in the upslope direction, B) mid- terrace position is the midpoint between two successive terraces, and C) up-terrace position refers to the location 50 cm from the lower wall of the upper terrace in the down slope direction. The 50 cm distance from both the lower and upper terrace wall was to reduce the effect of water accumulation and splash by the overtopping water, respectively. Figure 5.3 Terrace positions: (A) low-terrace, (B) mid-terrace, and (C) up-terrace 5.2.3 Soil sampling, laboratory analysis and reference data Following identification of sampling plots in the different slope categories and position within the terraces composite soil samples were collected along the terraces at 50 cm distance from the respective auger to 20 cm depth. The samples were thoroughly mixed, composited and bagged (2 kg samples) for laboratory analysis. Undisturbed soil samples were collected using a core ring for bulk density determination. In order to check the soil depth, auguring was continued to 120 cm depth at the center of the sampling plot unless restricted by lithic contact. Characterization and morphological description of properties less affected by the simmering effect of auger such as depth, 64

Performance of farmland terraces in soil fertility maintenance texture, consistency and color was done as per FAO standards (FAO 2006). Sampling was done from four slope categories, in four replicates (plots) and in three terrace positions (Table 5.1). Thus, a total of 48 samples were collected for laboratory analysis. Regarding bulk density sampling, three core ring samples could not be taken from one plot on the 15-30% slope due to the gravely soil there. Hence, the bulk density test was done only for 45 samples. Other management practices such as use of fertilizer, manure and compost and crop residue management was obtained from the seasonal monitoring records of the research station. Table 5.1 Farmland terrace soil sampling design Slope Replicates Total (%) Replicate 1 Replicate 2 Replicate 3 Replicate 4 samples 3-5 A B C A B C A B C A B C 12 5-8 A B C A B C A B C A B C 12 8-15 A B C A B C A B C A B C 12 15-30 A B C A B C A B C A B C 12* Grand total 48 Note: A = low-terrace, B = mid-terrace and C = up-terrace positions * Only 9 core ring samples were collected from plots in 15 – 30% slope range The composite soil samples were air dried, crushed and sieved through a 2 mm mesh. The main soil physical and chemical properties such as texture, pH, electrical conductivity (EC), organic carbon (OC), available phosphorus (av. P), total nitrogen (TN), exchangeable bases such as exchangeable calcium (Ca 2+ ), magnesium (Mg 2+ ), potassium (K + ) and sodium (Na + ) and cation exchange capacity (CEC) were determined from the composite samples while bulk density was determined from the core ring samples. Soil bulk density was determined by the Black (1965) method. Soil reaction (pH and EC) and soil particle-size distributions were determined using glass electrode and hydrometer, respectively by Van Reeuwijk (2002) method. OC was determined by the Walkley and Black (1934) method, TN by the Kjeldahl method as described in Black (1965) and available P by Olsen et al. (1954) methods. Exchangeable bases (Na + , K + Ca 2+ , and Mg 2+ ) and CEC were determined by the ammonium acetate method at pH 7 as described by Rowell (1994). The analysis was done at the National Soils Testing Laboratory in Addis Ababa, Ethiopia. Data from the MSCRS soil survey conducted before terracing in 1983 were used as a baseline (Weigel 1986). The profiles were grouped and selected according to 65

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