Phosphorus (P) availability and P transformation rates in Amazonian Dark Earth determined by 33P isotopic dilution.

Amazonian Dark Earth (ADE) often shows increased soil fertility compared to surrounding soils, likely linked to its increased concentration of soil organic matter and macronutrients such as phosphorus (P). For P, there is little knowledge whether the higher P availability is a result of increased biological processes (such as organic P mineralization) or physico-chemical processes (such as sorption/desorption), or both

Nitrogen budgets and soil nitrogen stocks of organic and conventional cropping systems: how reconcile efficiency and sustainability of nitrogen use?

Organic and conventional cropping systems differ in the nature and amounts of nitrogen (N) inputs, which may affect efficiency and sustainability of N use. In the DOK (bio-Dynamic, bio-Organic, Konventionell) field experiment, organic and conventional cropping systems have been compared since 1978 at two fertilization levels (with level 2 being typical for the respective system and level 1 receiving half of this dose)

Spring warming in Yukon mountains is not amplified by the snow albedo feedback

Decreasing spring snow cover may amplify Arctic warming through the snow albedo feedback. To examine the impact of snowmelt on increasing temperature we used a 5,000 m elevation gradient in Yukon, Canada, extending from valley-bottom conifer forests, through middle elevation tundra, to high elevation icefields, to compare validated downscaled reanalysis air temperature patterns across elevational bands characterized by different patterns of spring snowmelt. From 2000 to 2014 we observed surface warming of 0.01 °C/a·1,000 m in May (0.14 °C/a at 1,000 m to 0.19 °C/a at 5,000 m), and uniform cooling of 0.09 °C/a in June at all elevations. May temperature trends across elevationally dependent land cover types were highly correlated with each other despite large variations in albedo and snow cover trends. Furthermore, a clear dependency of infrared skin temperature on snow cover mediated albedo decline was observed in tundra, but this was insufficient to influence average diurnal air temperature. We observed negative June temperature trends which we attribute to increasing daytime cloud cover because albedo and snow cover trends were unchanging. We conclude that 8-day and monthly averaged Spring air temperature trends are responding to a synoptic external forcing that is much stronger than the snow albedo feedback in sub-Arctic mountains

Delivery of stable ultra-thin liquid sheets in vacuum for biochemical spectroscopy

The development of ultra-thin flat liquid sheets capable of running in vacuum has provided an exciting new target for X-ray absorption spectroscopy in the liquid and solution phases. Several methods have become available for delivering in-vacuum sheet jets using different nozzle designs. We compare the sheets produced by two different types of nozzle; a commercially available borosillicate glass chip using microfluidic channels to deliver colliding jets, and an in-house fabricated fan spray nozzle which compresses the liquid on an axis out of a slit to achieve collision conditions. We find in our tests that both nozzles are suitable for use in X-ray absorption spectroscopy with the fan spray nozzle producing thicker but more stable jets than the commercial nozzle. We also provide practical details of how to run these nozzles in vacuum

Land use change in Amazonian Dark Earth and Acrisol: responses of organic carbon, organic matter composition and microbial carbon utilisation.

The conversion of tropical forest for cassava cultivation is widely known to decrease the soil organic matter (OM) and nutrient contents of highly weathered soils in the tropics. Amazonian Dark Earth (ADE) might be affected less due to their historical anthropogenic amelioration with e.g. charcoal, ceramics and bones, leading to higher soil OM and nutrient concentrations. In this study, we analysed the effect of land use change on the OM dynamics and its composition under tropical conditions, using ADE and an adjacent Acrisol (ACR) as model systems

Consequences of land use change on soil organic matter composition and C-P relationships in Amazonian Dark Earth and Acrisol.

The conversion of tropical forest for cassava cultivation is widely known to decrease the soil organic matter (OM) and nutrient contents of highly weathered soils in the tropics. Amazonian Dark Earth (ADE) might be more resistant to this process due to their historical anthropogenic amelioration with e.g. charcoal, ceramics and bones, leading to higher soil OM and nutrient concentrations. In this study, we analyzed the effect of land use change on the OM dynamics under tropical conditions and how this is related with P distribution at the microscale, using ADE and an adjacent Acrisol (ACR) as model systems

NPK Bilanzen von ökologischer und konventioneller Landwirtschaft im Vergleich: Ergebnisse eines 35-jährigen Feldversuches

Die Ausreichende Verfügbarkeit von Stickstoff (N), Phosphor (P) und Kalium (K) ist essentiell für einen konstanten Ernteertrag in landwirtschaftlichen Systemen. Im DOK-Versuch in Therwil (Schweiz) wird seit 1978 ein Systemvergleich zwischen ökologischer und konventioneller Landwirtschaft im Rahmen eines Feldversuches betrieben. Die Verfahren biologisch-dynamisch (DYN) und organisch-biologisch (ORG) werden nur mit Stallmist gedüngt, während im konventionellen Verfahren (KON) zusätzlich mit Mineraldünger ausgeglichen wird. Im mineralisch gedüngten Verfahren (MIN) wird nur Mineraldünger ausgebracht, in der ungedüngten Kontrollfläche (NON) erfolgt seit Versuchsbeginn keine Düngung. Die Verfahren DYN, ORG und KON werden auf zwei Düngestufen geführt (2 = praxisübliche Düngung; 1 = halbe praxisübliche Dündung), Verfahren MIN nur auf Düngestufe 2. Ziel der Arbeit war es eine NPK Bilanz für den DOK-Versuch zu errechnen, um eine Abschätzung des Verlustpotentials bzw. von Nährstoffmangel der Feldfrüchte im jeweiligen Bewirtschaftungssystem zu ermöglichen. Die Nährstoffbilanz errechnete sich aus dem Vergleich jährlicher Eintrag minus jährlicher Austrag pro Versuchsparzelle. Berücksichtigte Einträge für die Elemente N, P und K waren: 1) Düngung, 2) Deposition, 3) Saatgut. Für N wurde zusätzlich die 4) symbiotische N-fixierung durch Leguminosen sowie der 5) Transfer von fixiertem N zu Gräsern, basierend auf vorhergehenden Studien im DOK Versuch, geschätzt. Berücksichtigte Austräge für die Elemente N, P und K waren: 6) Entzug durch Ernteprodukte sowie 7) Auswaschungsversluste. Für die Elemente N und P wurden zusätzlich die Bodenvorräte aus jährlichen (N) oder 7-jährlichen (P) Messungen in Ober- und Unterboden errechnet und mit den Ergebnissen der Bilanzierung in Beziehung gesetzt. Die wichtigsten Parameter der Nährstoffbilanzen waren die Faktoren Düngung sowie Entzug durch Ernteprodukte, wobei in der N-Bilanz auch die symbiotische N-fixierung und deren Transfer zu Gräsern eine gewichtige Rolle spielte. Die Ergebnisse der NPK-Bilanzierung deuten auf unterschiedliche Nährstofflimitierungen sowohl im Bezug auf die Verfahren, als auch auf den unterschiedlichen Düngestufen hin. Die Resultate werden in Bezug auf eine nachhaltige Bodennutzung in verschiedenen landwirtschaftlichen Systemen diskutiert

The DOK long-term experiment - lessons learned from 40 years of interdisciplinary research

The world’s growing population calls for sustainable food production within the limits of planetary boundaries. With respect to nitrogen and phosphorus cycling, the loss of biodiversity, land use change and the emission of greenhouse gases, four of these boundaries have been crossed already. Although fragmented knowledge of effects of different cropping systems on these focal planetary boundaries exists, there is a lack of comprehensive data from comparative cropping system experiments over the long run. Four decades back, farmers and researchers co-designed a system comparison experiment, located in Therwil (Basel-Land) Switzerland, comprising a seven-year ley crop rotation. Two conventional (with and without manure), and two organic systems (biodynamic and bioorganic) are compared. This experiment has served as a platform for national and international interdisciplinary research teams in the field of agronomy, soil quality, biodiversity, plant nutrition, food quality, sustainability assessment and modelling. Results of the 40years old DOK experiment show that organic systems, receiving distinctly less external inputs (chemical N, P, K and pesticides), maintained a higher biodiversity and produced lower greenhouse gas emissions. Yield averages over 40 years were 20% lower in organic systems across all crops. A nitrogen balance, including biological nitrogen fixation and stock changes of soil nitrogen, revealed a surplus for all manured systems, whereas the conventional system with sole mineral fertiliser was well balanced. Soil nitrogen stocks only increased slightly in the biodynamic system receiving composted manure. The biodynamic soil showed also increased soil organic carbon stocks, while the conventional soil receiving only mineral fertilizer acted as source for atmospheric CO2. A climate impact analyses encountering nitrous oxide, methane and soil organic matter changes resulted in lower CO2eq emissions in organic compared to the conventional systems, both area and yield scaled. Biodiversity and especially biomass of invertebrate fauna and plant seeds was enhanced in the organically managed systems. Our results demonstrate that organic cropping systems can contribute to a more sustainable production with respect to key planetary boundaries. To further improve system performance, yield gaps between organic and conventional systems need to be reduced by adapted cultivars, more effective organic plant protection and by closing urban and rural nutrient cycles

The UBA domain of conjugating enzyme Ubc1/Ube2K facilitates assembly of K48/K63‐branched ubiquitin chains

The assembly of a specific polymeric ubiquitin chain on a target protein is a key event in the regulation of numerous cellular processes. Yet, the mechanisms that govern the selective synthesis of particular polyubiquitin signals remain enigmatic. The homologous ubiquitin‐conjugating (E2) enzymes Ubc1 (budding yeast) and Ube2K (mammals) exclusively generate polyubiquitin linked through lysine 48 (K48). Uniquely among E2 enzymes, Ubc1 and Ube2K harbor a ubiquitin‐binding UBA domain with unknown function. We found that this UBA domain preferentially interacts with ubiquitin chains linked through lysine 63 (K63). Based on structural modeling, in vitro ubiquitination experiments, and NMR studies, we propose that the UBA domain aligns Ubc1 with K63‐linked polyubiquitin and facilitates the selective assembly of K48/K63‐branched ubiquitin conjugates. Genetic and proteomics experiments link the activity of the UBA domain, and hence the formation of this unusual ubiquitin chain topology, to the maintenance of cellular proteostasis