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5 years ago

Die Wirksamkeit von Boden

Die Wirksamkeit von Boden

Performance of farmland

Performance of farmland terraces in soil fertility maintenance (0.03%) for tangible differences in plant nutrition. Furthermore, nearly all terraces of all slope categories had the same TN mean difference (0.03 � mean �TN � 0.035). The explanation given above for OC differences across the terrain also holds true for TN. Table 5.3 Correlation between soil physico-chemical properties of farmland terraces pH Db Clay Na K Ca Mg CEC T.N. O.C Db 0.054 Clay 0.175 0.043 Na 0.376 ** 0.232 0.309 * K 0.327 * 0.005 0.147 0.562 ** Ca 0.121 -0.209 -0.076 0.087 -0.096 Mg 0.116 -0.219 0.232 -0.013 -0.144 0.307 * CEC -0.270 -0.305 0.030 -0.078 -0.267 0.339 * 0.502 ** T.N -0.410 ** 0.010 0.424 ** 0.043 -0.027 -0.314 * -0.026 0.188 O.C -0.404 ** -0.064 0.268 -0.018 -0.132 -0.352 -0.047 0.185 0.898 ** av P 0.132 -0.196 0.039 0.005 0.195 0.004 -0.092 -0.126 0.036 0.212 ** Correlation was significant at the 0.01 level (2-tailed). *. Correlation was significant at the 0.05 level (2-tailed). Values are Pearson correlation coefficient (r) n= 48 Soil available P contents (av. P = 12.1 ± 3.1 ppm, i.e., av. P = 12.1± 3.1g/ton) of the terraces was smaller than the absolute minimum. Watson and Mullen (2007) suggested that 15 ppm (15 g/ton) is a critical soil P concentration for categorizing the soil as P sufficient or deficient. But this does not mean same critical P value for all crops in all soil types where the levels vary with crop and soil types (Bergmann 1992; Sys et al. 1993). The lower plant available P could be attributed to inherent soil properties such as P fixation by iron and aluminum, while the differences between the terraces across slope of the terrain could be related to organic matter (OM) input differences. Higher OC, TN and available P contents were observed on terraces located at moderately steep slope positions. Texture and bulk density contribute to crop productivity as they affect soil physical fertility (Hamza and Anderson 2002; Rasool et al. 2007). The soil physical properties influence soil water movement, root penetration and nutrient uptake (Hamza and Anderson 2002; Rasool et al. 2007). Erosion and deposition processes also modify soil physical characteristics (Chen et al. 1997; Vancampenhout et al. 2006). The analyses in the present study revealed statistically significant (P < 0.01) soil texture differences between terraces located on different slopes. However, soils did not show 74

Performance of farmland terraces in soil fertility maintenance significant bulk density differences with slope change. The content of sand particles in the soils statistically significantly increased with increase in slope of the terrain (Figure 5.7). Terraces on 8-30% had statistically significantly higher (P � 0.01) sand content than on the 3-8% slopes. However, terraces in successive slope categories both on 3-8% and 8-30% slopes showed non-significant differences (Table 5.2). Terraces on the 5-8% slopes had statistically significantly higher (P < 0.07) silt contents than terraces on the 3-5% and 8-30% slopes. In contrast, clay content decreased with slope increase. Terraces on the 3-8% slope had significantly higher (P � 0.023) clay contents than terraces on the 8-30% slope. The mean clay content differences varied from 5% to 6%. Terraces on the sloping (5 - 8%) terrain had statistically significantly higher clay contents than terraces on 8-15% slope, with 6% mean difference. Figure 5.7 Soil textures of terraces across slope of the terrain Soil texture differences between terraces at different slope could be related to erosion and deposition processes. The highest silt content was measured in soils on sloping terrain may be resulted to erosion and sedimentation processes, as there could be a balance between soil particle detachment, runoff velocity and deposition. Sheet 75