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Stuttgart Mühlhausen, Germany

Georgiadis A.,University of Hohenheim | Sauer D.,University of Hohenheim | Sauer D.,TU Dresden | Breuer J.,Center for Agricultural Technology Augustenberg | And 3 more authors.
Soil Research | Year: 2015

This study focuses on optimising amorphous silica extraction from soils by using NaOH. Based on the results of this test series, a method for quantifying amorphous silica in soils from temperate-humid climate is proposed. All tests were carried out on materials of known composition (well-defined samples of feldspar, clay minerals, bio-opal, silica gel, and mixtures of these components) and on soil samples, to determine the optimum set of conditions, in terms of solid:solution ratio, temperature and extraction time, for dissolving amorphous silica without considerably attacking other solid silicon compounds. A solution of 0.2m NaOH almost completely extracted amorphous silica, and when applied at room temperature and a solid:solution ratio of 1:400, only slightly broke down crystalline Si compounds. The predictable and reproducible underestimation was considered more acceptable than the variable partial dissolution of silicates that occurs during extraction at higher temperatures. We therefore recommend using this method on soils from temperate-humid climate to estimate the amorphous Si fraction. © 2015 CSIRO. Source

Schittenhelm S.,Julius Kuhn Institute | Reus D.,Justus Liebig University | Kruse S.,Center for Agricultural Technology Augustenberg | Hufnagel J.,Leibniz Center for Agricultural Landscape Research
Journal fur Kulturpflanzen | Year: 2011

Double-crop (DC) systems are receiving serious consideration as cropping alternative for agricultural biomass production in Germany. In this study the productivity and economics of DC and sole-crop (SC) systems were compared from 2007 to 2009 at three climatically diverse sites of Germany. The warm season crops maize (Zea mays L.), forage sorghum [Sorghum bicolor (L.) Moench] and sor-ghum-sudangrass [S. bicolor (L.) Moench × S. sudanense (Piper) Stapf] were either grown as sole crops or as second crop following winter rye (Secale cereale L.). The winter rye first crop was harvested premature at early-to-mid May (early) or early June (late). While the winter rye was grown under rainfed conditions, maize, forage sorghum, and sorghum-sudangrass were grown with or without irrigation. Winter rye produced an aboveground dry matter yield (DMY) of 5.2 t ha -1 at early harvest and 9.0 t ha -1 at late harvest. The highest yielding DC system (rye-maize) out-yielded the most productive SC system (maize) by 3.6 t ha -1 (23%) under rainfed conditions and by 5.2 t ha -1 (24%) with irrigation. Irrigation increased DMY of sole crops by 5.3 t ha -1 (37%), of early sown second crops by 5.6 t ha -1 (43%), and of late sown second crops by 6.8 t ha -1 (77%). Under rainfed conditions, the higher DMY of the DC as compared with the SC systems did not compensate the higher production costs. With irrigation, however, the rye-maize DC achieved higher contribution margins than SC maize at two of the three experimental sites. Source

Morhart C.,Albert Ludwigs University of Freiburg | Sheppard J.,Albert Ludwigs University of Freiburg | Seidl F.,Center for Agricultural Technology Augustenberg | Spiecker H.,Albert Ludwigs University of Freiburg
Forests | Year: 2013

In this study the influence of three different tillage systems in combination with eight varying weed treatments applied within the establishment year and its effect on the final above ground leafless biomass production (after the third growing season) of short rotation coppice poplar is presented. The three tillage systems included variants with ploughing and harrowing, variants with cultivation and ley cropping and variants without tillage. Weed treatments included the application of different herbicides, but also more environmentally sound variants such as mulching and the use of mulch materials to avoid the use of herbicides. To estimate the influence on final biomass production, regression analysis was undertaken using DBH as the predictor variable. Based on 1056 DBH measurements the biomass production of the different variants was compared. The interactions of tillage system and weed treatment on biomass yield were found to be statistically significant. Between tillage systems the ploughing variant displayed a better overall performance than the cultivation with ley crop variant and the variant without any tillage. Differing weed treatments reveal greater success for the whole area application of herbicides than band application, both being better than the use of mulch materials. These results suggest that the right tillage system in combination with effective chemical weed control is the key to the successful establishment of Short rotation coppice (SRC) poplar plantation following the principles of an integrated weed management approach. Furthermore, ecological variants such as ploughing in combination with the use of mulch materials and mechanical vegetation control between the rows could be a solution to reduce dependence on chemical control. However, this comes at the expense of a considerable loss in yield. © 2013 by the authors. Source

Schuler H.,University of Natural Resources and Life Sciences, Vienna | Bertheau C.,University of Natural Resources and Life Sciences, Vienna | Egan S.P.,University of Notre Dame | Feder J.L.,University of Notre Dame | And 11 more authors.
Molecular Ecology | Year: 2013

The widespread occurrence of Wolbachia in arthropods and nematodes suggests that this intracellular, maternally inherited endosymbiont has the ability to cross species boundaries. However, direct evidence for such a horizontal transmission of Wolbachia in nature is scarce. Here, we compare the well-characterized Wolbachia infection of the European cherry fruit fly, Rhagoletis cerasi, with that of the North American eastern cherry fruit fly, Rhagoletis cingulata, recently introduced to Europe. Molecular genetic analysis of Wolbachia based on multilocus sequence typing and the Wolbachia surface protein wsp showed that all R. cingulata individuals are infected with wCin2 identical to wCer2 in R. cerasi. In contrast, wCin1, a strain identical to wCer1 in R. cerasi, was present in several European populations of R. cingulata, but not in any individual from the United States. Surveys of R. cingulata from Germany and Hungary indicated that in some populations, the frequency of wCin1 increased significantly in just a few years with at least two independent horizontal transmission events. This is corroborated by the analysis of the mitochondrial cytochrome oxidase II gene that showed association of wCin1 with two distinct haplotypes in Germany, one of which is also infected with wCin1 in Hungary. In summary, our study provides strong evidence for a very recent inter-specific Wolbachia transmission with a subsequent spatial spread in field populations. © 2013 John Wiley & Sons Ltd. Source

Schuler H.,University of Natural Resources and Life Sciences, Vienna | Arthofer W.,University of Innsbruck | Riegler M.,University of Western Sydney | Bertheau C.,University of Natural Resources and Life Sciences, Vienna | And 5 more authors.
Entomologia Experimentalis et Applicata | Year: 2011

Rhagoletis pomonella Walsh (Diptera: Tephritidae) is a model species for sympatric speciation through host race formation on apple and hawthorn. The bacterial endosymbiont Wolbachia, a manipulator of arthropod reproduction, has been considered to contribute to speciation in several species. A potential role of Wolbachia in sympatric speciation of R. pomonella remains to be tested despite an earlier detection by PCR. In this study, we isolated Wolbachia from R. pomonella individuals from both host species using multi-locus sequence typing (MLST) and the surface protein wsp. By cloning and sequencing of 311 plasmids, we found sequence types of at least four wPom strains. A complete MLST profile was obtained only for wPom1, whereas MLST loci of the other putative strains were difficult to assign because of multiple infections and low sample numbers. wPom1 occurs in both host races, whereas different sequence types were found at low frequencies only in apple-infesting R. pomonella. This warrants further investigation as it cannot be excluded that Wolbachia plays a part in this model of sympatric speciation. © 2011 The Authors. Entomologia Experimentalis et Applicata © 2011 The Netherlands Entomological Society. Source

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