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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 terrain. Soil pH and exchangeable bases increased with decrease in slope. The increases were due to erosion and leaching of soluble salts from the upper slope and accumulation at the down-slope terrain positions (Chen et al. 1997; Olarieta et al. 2008). Higher soil OC, TN and av. P contents were observed on terraces located on moderately steep slopes. Hence, the terraces received higher organic matter input from the non-arable areas. Significant soil texture differences across the terrain, which indicates that terracing does not completely prevent soil texture gradients. Unlike in other studies (Dercon et al. 2003; Gebermichael et al. 2005; Vancampenhout et al. 2006), the topsoil physico-chemical properties except bulk density did not show significant differences within a terrace. With development of bench terraces, incoming runoff was uniformly distributed within a terrace, which reduced soil fertility gradients. The mid-terrace position had a significantly higher bulk density (0.4 gm/cm 3 ) than the other positions of the terraces. This can be attributed to balanced soil aggregate deposition, which resulted soil particles packing (Keller and Håkansson 2010). Comparison of the 1983 and the current soil survey data revealed nearly stable soil fertility status with very slight changes. Accordingly, pH and TN improved slightly, while OC, av. P, exchangeable bases and bulk density showed a slightly declining trend. The negative balance of some soil nutrients could be due to continued nutrient removal through crop harvest and due to the fact that terracing did not completely stop erosion. The smaller negative balances and only slight improvement in some nutrients indicate that farmland terracing reduced not only soil loss but also nutrient loss. In general, terracing had a number of advantages with respect to reducing soil and soil nutrient loss through erosion; however, terracing alone does not maintain soil fertility. In order to improve soil fertility, terracing should be supplemented by appropriate organic and inorganic fertilizer application according to the site-specific fertility level. Therefore, in this study the following can be concluded concerning the impact of farmland terracing on soil fertility maintenance: i. Due to regular maintenance and sedimentation, terraces develop to bench terraces, and grasses grown on the terrace wall increased its stability. ii. With development of bench terraces, topsoil fertility gradients were remarkably minimized, but care should be taken in the interpretation of the above statement 82

Performance of farmland terraces in soil fertility maintenance because soil volume and nutrient storage gradients exist within a terrace due to soil depth differences developed at the earlier stage of terrace. iii. Performance of terracing to reduce soil erosion and fertility vary with terrain. Terracing was more effective in maintaining soil fertility on up to strongly sloping lands (

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