Additive unit representations in global fields - A survey

We give an overview on recent results concerning additive unit representations. Furthermore the solutions of some open questions are included. The central problem is whether and how certain rings are (additively) generated by their units. This has been investigated for several types of rings related to global fields, most importantly rings of algebraic integers. We also state some open problems and conjectures which we consider to be important in this field.Comment: 13 page

DOC trail: soil organic matter quality and soil aggregate stability in organic and conventional soils

Conclusion Soil organic matter quality is affected by the agricultural systems of the DOC trial. System effects on the chemical composition, however, were smaller than those on the living organisms in soil and their functions. A close correlation was found between soil structure and microbial biomass indicating that microbes are playing an important role in soil structural stability

Enhanced soil quality with reduced tillage and solid manures in organic farming - a synthesis of 15 years

Demands upon the sustainability of farming are increasing in step with climate change and diversity loss. Organic farming offers a viable approach. To further improve organic management, three strategies with potential to enhance soil quality are being tested in a long-term trial since 2002 on a clay loam in temperate Switzerland: reduced tillage vs. ploughing, solid vs. liquid manures and biodynamic preparations. A synthesis of 15 years reveals an increase in topsoil organic carbon (SOC, +25%), microbial biomass (+32%) and activity (+34%) and a shift in microbial communities with conversion from ploughing to reduced tillage. Soils under reduced tillage are more stratified in SOC and nutrients. Additional application of composted manure has increased SOC by 6% compared to pure slurry application, with little impact on soil microbes. Biodynamic preparations have had a minor impact on soil quality. Fertilisation and biodynamic preparations did not affect yields. Both higher and lower yields were harvested in the reduced tillage system in relation to ploughing. The main yield determinants were N supply and higher weed infestation under reduced tillage. Continuously reduced tillage in organic farming has been proven to enhance soil quality at this site, while also presenting more challenges in management

Neuer Langzeitversuch über Bodenbearbeitung, Düngung und Präparate

In den ersten drei Jahren hat der seit 2002 laufende Langzeitversuch Frick (Schweiz) bereits viele spannende Ergebnisse zu Tage gefördert. Unerwartet war, dass Weizen, der in Parzellen gewachsen war, welche lediglich im Versuchsjahr mit biologisch-dynamischen Präparaten behandelt wurden, weniger Fusarientoxine enthielt und mit den bildschaffenden Methoden klar von nicht behandelten Weizenproben unterschieden werden konnte. Sehr bedeutsam sind auch die Ergebnisse zur Bodenfruchtbarkeit: Reduziert bearbeitete Böden waren schon nach kurzer Zeit belebter, wiesen etwas mehr Humus auf und auch die Symbiosepilze fühlten sich dort wohler als in gepflügten Böden. Die Erträge reagierten je nach Kultur positiv oder negativ auf reduzierte Bodenbearbeitung. Allerdings könnten sich bei dieser Bodenbearbeitung Wur-zelunkräuter zu einem ernsthaften Problem entwickeln. Wie sich die Erträge und die Unkrautsituation entwickeln, müssen weitere Untersuchungsjahre zeigen. Die FiBL-Forscher erwarten, dass sich die Differenzen zwischen den Verfahren im Verlaufe der nächsten Versuchsperiode noch stärker zeigen. Der Abschluss des Versuchs ist auf das Jahr 2011 geplant

Entwicklung von pfluglosen Anbauverfahren im ökologischen Landbau unter Anwendung verschiedener Hofdüngerformen und biologisch-dynamischer Präparate

In a long-term field trial (November 2002-2011), located in Frick near Basle (Switzerland), the influence of reduced tillage on soil fertility and yield is studied in a crop rotation under organic farming conditions. Here, we describe the field experiment and present results of the first year. The three factors examined, soil tillage, manure type and biodynamic preparations are implemented in a fully factorised experimental setup. The experimental field manifested a high homogeneity for the parameters pH, soil organic carbon (Corg), dehydrogenase activity and microbial biomass. Wheat yield in the first experimental year was 16% higher in ploughed plots than in the plots with reduced tillage (p < 0.001). Plots fertilised with slurry manifested 5 % (p < 0.001) higher wheat yields than plots manured with compost. Yield of the following oat/clover intercrop was somewhat higher in reduced tilled plots than in ploughed plots, but not statistically significant. Long-term effects need to be evaluated

An Overview of Anorthosite-bearing Layered Intrusions in the Archaean Craton of Southern West Greenland and the Superior Province of Canada: Implications for Archaean Tectonics and the Origin of Megacrystic Plagioclase

Anorthosite-bearing layered intrusions are unique to the Archaean rock record and are abundant in the Archaean craton of southern West Greenland and the Superior Province of Canada. These layered intrusions consist mainly of ultramafic rocks, gabbros, leucogabbros and anorthosites, and typically contain high-Ca (\u3eAn70) megacrystic (2–30 cm in diameter) plagioclase in anorthosite and leucogabbro units. They are spatially and temporally associated with basalt-dominated greenstone belts and are intruded by syn-to post-tectonic granitoid rocks. The layered intrusions, greenstone belts and granitoids all share the geochemical characteristics of Phanerozoic subduction zone magmas, suggesting that they formed mainly in a suprasubduction zone setting. Archaean anorthosite-bearing layered intrusions and spatially associated greenstone belts are interpreted to be fragments of oceanic crust, representing dismembered subduction-related ophiolites. We suggest that large degrees of partial melting (25–35%) in the hotter (1500–1600 °C) Archaean upper mantle beneath rifting arcs and backarc basins produced shallow, kilometre-scale hydrous magma chambers. Field observations suggest that megacrystic anorthosites were generated at the top of the magma chambers, or in sills, dykes and pods in the oceanic crust. The absence of high-Ca megacrystic anorthosites in post-Archaean layered intrusions and oceanic crust reflects the decline of mantle temperatures resulting from secular cooling of the Earth