Comparison of uniform control and site-specific model-based nitrogen prescription in terms of grain yield, nitrogen use efficiency and economic aspects in a heterogeneous corn field

Im letzten Jahrzehnt ist die Anbaufläche zur Maisproduktion in Europa und insbesondere in Deutschland, kontinuierlich angestiegen. Zahlreiche Studien zeigen, dass die Maisproduktion mit einem hohen Risiko der Stickstoffauswaschung verbunden ist, weshalb die gegenwärtige Strategie des Stickstoffmanagements überprüft und mit neuen Managementstrategien verglichen werden muss. Ziel dieser Studie war, eine einheitliche (Kontrolle) und eine teilflächenspezifische (Modell-basierte) Strategie des Stickstoffmanagements hinsichtlich Kornertrag, Stickstoffnutzungseffizienz und ökonomischen Aspekten der Maisproduktion zu untersuchen und zu bewerten. Auf der Versuchsstation der Universität Hohenheim wurde über einen Zeitraum von drei Jahren (2006–2008) ein entsprechender Feldversuch durchgeführt. Die Aufwandmenge für Stickstoff wurde innerhalb des Schlages variiert, um die vorhandene Heterogenität des Schlages zu berücksichtigen. Das Pflanzenwachstumsmodell APOLLO wurde eingesetzt, um mit Hilfe (teilflächenspezifischer) Eingangsdaten, wie Bodentextur, Wetter, Sorte, Management und historischen Ertragsdaten den Kornertrag des Mais in Abhängigkeit unterschiedlicher Stickstoffdüngermengen zu ermitteln. Für das Versuchsdesign wurde der Schlag in 48 Managementeinheiten unterteilt. In jeder dieser Managementeinheiten wurden die einheitliche Kontrolldüngung und die teilflächenspezifische (Modell-basierte) Düngung ausgebracht. Für die Ausbringung des Stickstoffdüngers wurde eine Applikationskarte erstellt, anhand derer in der Kontrollvariante 130 kg N ha–1 und in der Modell-basierten Variante 100–210 kg N ha–1 (entsprechend der Simulationsergebnisse des Pflanzenwachstumsmodells) ausgebracht wurden. Der Kornertrag des Mais wurde mit Hilfe der Ertragskartierung des Mähdreschers erfasst. Die unterschiedlichen Strategien des Stickstoffmanagements resultierten in geringen Ertragsvorteilen der Modell-basierten Variante, verglichen mit der Kontrollvariante. Hinsichtlich des Kornertrags und des Nettoertrags lagen signifikante Unterschiede zwischen den beiden Stickstoffmanagement-Strategien vor. Hinsichtlich der Stickstoffnutzungseffizienz konnten allerdings keine signifikanten Unterschiede zwischen der Kontrolle und der Modell-basierten Variante ermittelt werden. Um den Kornertrag in Mais unter Berücksichtigung der vorherrschenden Heterogenität des Schlages zu optimieren, müssen weitere ertragslimitierende Faktoren untersucht werden.    In Europe, and especially in Germany, the land area cultivated with corn over the last decade has continuously been increasing. Several studies indicated that corn production has a high risk of nitrogen leaching, thus the current nitrogen management strategy needs to be verified and compared with new management strategies. The objective of this study was to investigate and to evaluate uniform (control) and model-based (site-specific) nitrogen management strategies in terms of corn grain yield, nitrogen use efficiency and economic aspects. Field trials were conducted at an experimental station as part of Hohenheim University over a three-year period (2006–2008). Nitrogen application rate was varied to meet the given heterogeneity on the field. The crop growth model APOLLO was employed with using (site-specific) input data, including soil texture, weather, cultivar, management and historical yield data, in order to model corn yield depending on nitrogen fertilization rate variations. In the experimental design, the field was separated in 48 management units. Within each management unit, a uniform control treatment and a site-specific model-based treatment were applied. For the nitrogen application, a map was created and the fertilizer was broadcast accordingly at 130 kg N ha–1 for uniform control treatment and 100–210 kg N ha–1 for the site-specific treatment in line with the model results. Corn grain yield was acquired with a yield-mapping device on a combine harvester. The two different nitrogen management strategies resulted in yield advantages for the model-based treatment compared to the uniform control treatment. Concerning corn grain yield and marginal net return, significant differences were determined between both nitrogen treatments. However, no significant differences were found for nitrogen use efficiency between the uniform control and the site-specific model-based nitrogen treatments. Further investigations of yield driving factors need to be performed in order to optimize corn grain yield according to a given within field heterogeneity.   &nbsp

Investigation and Modeling of the Optimization Potential of Adapted Nitrogen Fertilization Strategies in Corn Cropping Systems with Regard to Minimize Nitrogen Losses

Das Ziel der Arbeit war die "Untersuchung und Modellierung des Optimierungspotentials von angepassten Stickstoff-Düngungsstrategien in Mais Anbausystemen in Hinblick auf Stickstoffverluste". Der Hintergrund der Arbeit liegt in der steigenden Umweltbelastung durch die Landbewirtschaftung. Aus diesem Grund war die Dissertation in den Kontext des Graduiertenkollegs "Strategien zur Vermeidung der Emission klimarelevanter Gase und umwelttoxischer Stoffe aus Landwirtschaft und Landschaftsnutzung" an der Universität Hohenheim eingegliedert. Die Zielsetzung des Graduiertenkollegs war die Entwicklung von Methoden zur Quantifizierung und die Modellierung der Entstehung und der Emission von klimarelevanten Gasen und umwelttoxischen Stoffen aus der Landwirtschaft und Landnutzung und die ökonomische Bewertung praktikabler Vermeindungsstrategien. Um das Optimierungspotential von angepassten Stickstoff-Düngungsstrategien in Mais zu ermitteln, wurde die Arbeit wurde folgendermaßen gegliedert: 1. Untersuchung der räumlichen Variabilität und zeitlichen Stabilität von Maiserträgen auf drei Schlägen im Oberrheingraben. 2. Ermittlung der zu Grunde liegenden ertragslimitierenden Faktoren in allen Schlägen mittels einfacher und komplexer Modelle. 3. Entwicklung angepasster Stickstoffdüngestrategien unter der Berücksichtigung von Ertragsvariabilität und den ertragslimitierender Faktoren. Das Untersuchungsgebiet war im Oberrheingraben angesiedelt, welches als eine Region intensiver Maisproduktion gekennzeichnet ist. Gleichzeitig gehört die Region entlang des Rheins zu den bedeutendsten Trinkwassergebieten Europa. Daraus ergaben sich in den letzten Jahrzehnten der Konflikt zwischen intensiver Landbewirtschaftung verbunden mit hohen Einträgen an Düngemitteln auf der einen Seite und der Schutz der Grundwasservorkommen auf der anderen Seite. Die Untersuchungen wurden auf drei Praxisschläge bei Weisweil nordwestlich von Freiburg, Deutschland, durchgeführt. Auf allen drei Schlägen wurde seit 1998 Mais in Monokultur angebaut. In den Untersuchungen im Oberrheingraben konnte eine räumliche und zeitliche Variabilität der Kornerträge ermittelt werden. Die unterschiedlichen Ertragsmuster in jedem Schlag lassen ertragslimitierende Wachstumsbedingungen vermuten. Einerseits schien der Ertrag beeinflusst durch die zeitliche Variation von Sorte, Klima und Management, sowie durch räumlich Variation möglicher ertragslimitierender Faktoren, wie Nährstoff- und Wasserverfügbarkeit auf der anderen Seite. Um die Managementstrategien anzupassen, müssen die zu Grunde liegenden ertragslimitierenden Faktoren innerhalb der drei Schläge ermittelt werden. Über die erfassten Pflanzenparameter konnte die gemessene Ertragsvariabilität nicht erklärt werden, wohingegen Korrelationen zwischen Bodeneigenschaften und den ermittelten Ertragsvariabilitäten innerhalb der drei Schläge gezeigt werden konnten. Signifikante Zusammenhänge wurden zwischen Bodennährstoffen, Bodeneigenschaften und dem Ertrag ermittelt. Aufgrund dieser Ergebnisse scheinen die Bodeneigenschaften die Haupteinflussfaktoren für die gemessene Ertragsvariabilität auf den drei Schlägen im Oberrheingraben zu sein. Trotz allem konnte über einfache Regressionsmodelle nur ein Teil der Ertragsvariabilität erklärt werden. In einem nächsten Schritt wurden komplexe Wachstumsmodelle eingesetzt, um die Ertragsvariabilität innerhalb der Schläge zu simulieren und die zu Grunde liegenden Faktoren zu ermitteln. Das eingesetzte prozess-orientierte Modell APOLLO (Application of Precision Agriculture for Field Management Optimization) wurde auf Grundlagen von CERES und CROPGRO entwickelt. Innerhalb des Modells könnten unterschiedliche Bodeneigenschaften angepasst werden und somit das Modell kalibriert werden. Die Ergebnisse haben gezeigt, dass mittels APOLLO die Ertragsvariabilität gut wider gegeben werden kann. Als Ursachen für die Variabilität wurden vor allem Unterschiede in der Bodenverdichtung und der Durchwurzelbarkeit des Bodens angenommen. Die Korrelationen zwischen simuliertem und gemessenem Ertrag geben Auskunft über die Ausprägung der ertragslimitierenden Faktoren. Die Kalibrierung war unter anderem abhängig von der gewählten Größe der Grids. Kleine Grids konnte die Ertragsvariabilität stärker abbilden, wohingegen größere Grids die Ertragsmuster deutlich wiedergaben. Infolge dessen konnte eine bessere Kalibrierung des Modells erzielt werden, wenn die Erträge aus größeren Grids zu Grunde gelegt wurden. Das APOLLO-Modell wurde des Weiteren auch zur Entwicklung der Stickstoff-Düngeempfehlung eingesetzt. Über einen Zeitraum von 28 Jahren wurde die aktuelle Stickstoff Düngestrategie der Landwirte simuliert. Zusätzlich wurden über das APOLLO-Modell auch eine optimierte einheitliche und eine optimierte variable Stickstoff-Düngestrategien entwickelt. Die Düngestrategien wurden unter Berücksichtigung von langjährigen Wetterverhältnissen (28 Jahre) untersucht. Die Strategien wurden anhand von simuliertem Ertrag, simulierter Nitratauswaschung und simulierten ökonomischen Gesichtspunkten bewertet. Dabei wurde deutlich dass die angepassten Düngestrategien (optimiertes einheitliches Management und variable angepasstes Management) gegenüber der aktuellen Düngestrategie von Vorteil waren. Insbesondere dann, wenn die Düngestrategien für unterschiedliche Wetterbedingungen (Trocken, normal und nasse Jahre) entwickelt wurden. Die angepassten Düngestrategien führten zu einer Reduzierung des Reststickstoffes im Boden und somit zu einem verringerten Risiko der Nitratauswaschung. Auch für die gasförmigen Stickstoffverluste konnte in Optimierungspotential ermittelt werden. Die Ergebnisse zeigten eine verringerte kumulative Denitrifizierungsrate unter angepasster Düngestrategie verglichen mit der aktuellen Düngestrategie. Zusammenfassend kann gesagt werden, dass die Anwendung einer angepassten Düngestrategie (optimiertes einheitliches Management und variable angepasstes Management) zu einer Reduzierung von Stickstoffverlusten, in Form von Nitratauswaschung und Stickstoffemissionen führen kann. Generell, ist das Optimierungspotential aber abhängig vom jeweiligen Anbausystem und damit größer, wenn ein Anbausystem einem gesteigerten Verlustpotential für Stickstoff unterliegt.The aim of this study was the "Investigation and Modeling of the Optimization Potential of Adapted Nitrogen Fertilization Strategies in Corn Cropping Systems with Regard to Minimize Nitrogen Losses". The background for the investigation could be seen in the increasing number of environmental pollution by agricultural land use. The dissertation was embedded in the context of the Graduiertenkolleg "Strategies to Reduce the Emission of Greenhouse Gases and Environmental Toxic Agents from Agriculture and Land Use" at the University of Hohenheim. The objective of this Graduiertenkolleg was to develop methods for quantifying and modeling the origin and the emission of greenhouse gases and environmentally toxic agents from agriculture and land use and for assessing them economically in the sense of practicable avoidance strategies. In order to determine the optimization potential of adapted nitrogen fertilization strategies in corn the study was organized in the following parts: 1. Investigation of the spatial variability and temporal stability of corn grain yield on three fields in the Upper Rhine Valley. 2. Determination of underlying yield-limiting factors in each field by the use of simple and complex models. 3. Development of adapted nitrogen fertilization strategies in consideration of the yield variability and the underlying yield-limiting factors. The area of investigation was located in the Upper Rhine Valley, which is characterized as a region with intense corn cultivation. At the same time this region belongs to the most important water protection areas in Europe. Thus, a conflict between agricultural land use associated with high fertilizer inputs on one hand and the protection of water bodies on the other hand rose, because measured nitrate concentrations in the groundwater increased constantly within the last decades. The study was conducted on three farm fields in the boundary of Weisweil, which is located northwest of Freiburg, Germany. Since 1998 the three fields were planted continuously with corn. In a 7-year field experiment spatial variability and stability of yield could be indicated. The determined yield pattern in each field raised assumptions about varying growth conditions within and among the fields. Thus, on the one hand the corn yield seemed to be influenced by temporal variations in cultivar, climate and management and by spatial and temporal variation of possible yield-limiting factors like nutrient availability or water supply on the other hand. In order to optimize management strategies the underlying yield-limiting factors causing the spatial and temporal yield variability needed to be determined in these three fields. Whereas plant yield parameters did not explain the existing yield variability very well, soil characteristics were identified as the major factors affecting the observed yield variability in all three fields. Significant relationships were found between combinations of soil nutrient levels, soil characteristics and yield. Based on these results, it appeared that soil characteristics were the primary factor affecting spatial yield variability in the three farmer fields in the Upper Rhine Valley. However, some of the spatial yield variability remained unexplained by simple regression analysis. In a more complex approach crop growth models were implemented to simulate the spatial yield variability within the field and to get information about the underlying yield-limiting factors. Therefore the process-oriented crop growth model APOLLO was implemented to evaluate the causes of spatial yield variability of corn in the three fields. APOLLO (Application of Precision Agriculture for Field Management Optimization) is a precision farming decision support system, which is based on the CERES and CROPGRO family of crop growth models and includes different soil parameter to calibrate the model. In general the APOLLO model performed well in simulating spatial yield variability in the fields. The results indicated that the spatial yield variability was mainly affected by a varying restrictive layers and reduction of root growth within the three fields. The correlation between simulated and measured yields provided information about the strength of the soil parameter affecting the yield within these fields. The calibration results were influenced by the grid size. Whereas smaller grids provided more random monitor yield data, larger grids provided a more representative set of yield monitor data, due to the coverage of a larger area. Consequently, the APOLLO model performed better when yields belonging to larger grids were used for model calibration. The applicability of the APOLLO model can be extended by developing prescriptions for different management strategies and thus enhancing the possibilities of successfully implementing site-specific management strategies. Thus, APOLLO was used to simulate the current uniform nitrogen management strategy of the producers in Weisweil over a 28-year period. Additionally an optimum uniform management and an optimum variable-rate management were developed and simulated. For these strategies also the different weather pattern were taken into account. All three strategies were evaluated based on the simulated yield, the simulated leaching potential and the simulated economics. It was obvious, that variable-rate nitrogen fertilization strategies were most advantageous compared to the other strategies, especially, when the nitrogen application rates were differentiated for dry, normal and wet weather scenarios. Adapted nitrogen fertilization strategies, as optimum uniform management and variable-rate management indicated a potential to reduce the amount of nitrogen, which is left in the soil after harvest, and associated that the potential nitrate leaching was reduced. In a case study the cumulative denitrification under these weather and fertilization scenarios over the growing season was simulated. The results indicated a reduction of cumulative denitrification under adapted fertilization strategies when compared to current uniform management. Summarizing, the results of this study suggest, that the implementation of adapted fertilization strategies (especially the variable-rate management of nitrogen) could lead to a reduction of nitrogen losses, as nitrogen leaching and nitrogen emissions could be minimized. Generally, the optimization potential for adapted nitrogen fertilizer strategies (optimum uniform management and variable-rate management) could be improved for cropping systems that were associated with higher risk for nitrogen losses

Beeinflussung der generativen Vermehrung von Rumex obtusifolius durch produktionstechnische Maßnahmen

Rumex obtusifolius produces a large number of long living seeds. Therefore, all means to reduce seed production or establishment of seedlings from seeds are impor-tant. The data of this paper show that in grassland a high soil seed bank not necessar-ily leads to a high infestation with dock. There are options to interfere seed production and establishment of seedlings. The cutting regime may have an impact on seed production. Establishment of seedlings can be minimized by avoiding gaps in the vegetation canopy

Impact of differentiated macrophage-like cells on the transcriptional toxicity profile of cuo nanoparticles in co-cultured lung epithelial cells

To mimic more realistic lung tissue conditions, co-cultures of epithelial and immune cells are one comparatively easy-to-use option. To reveal the impact of immune cells on the mode of action (MoA) of CuO nanoparticles (NP) on epithelial cells, A549 cells as a model for epithelial cells have been cultured with or without differentiated THP-1 cells, as a model for macrophages. After 24 h of submerged incubation, cytotoxicity and transcriptional toxicity profiles were obtained and compared between the cell culture systems. Dose-dependent cytotoxicity was apparent starting from 8.0 µg/cm$^{2}$ CuO NP. With regard to gene expression profiles, no differences between the cell models were observed concerning metal homeostasis, oxidative stress, and DNA damage, confirming the known MoA of CuO NP, i.e., endocytotic particle uptake, intracellular particle dissolution within lysosomes with subsequent metal ion deliberation, increased oxidative stress, and genotoxicity. However, applying a co-culture of epithelial and macrophage-like cells, CuO NP additionally provoked a pro-inflammatory response involving NLRP3 inflammasome and pro-inflammatory transcription factor activation. This study demonstrates that the application of this easy-to-use advanced in vitro model is able to extend the detection of cellular effects provoked by nanomaterials by an immunological response and emphasizes the use of such models to address a more comprehensive MoA

Tracer Survey in the Cape Verde Region Traceraufnahme in der Kapverdenregion Cruise No. 10, Leg 1 October 31 – December 06, 2008 Ponta Delgada (Portugal) – Mindelo (Cape Verde Islands)

The research cruise MSM10/1 was extremely successful. All programs were able to collect high quality data and the anticipated goals of the expedition were fully met. We have been able to carry out the first comprehensive survey of a tracer release in the Guinea Upwelling region (GUTRE) roughly seven month after the tracer was released at 8°N 23°W in April 2008. We have estimated that a total of 40% of the tracer was found during this cruise. While the horizontal spreading and mixing was larger than anticipated, the vertical extent of the tracer found was small. The low vertical tracer spreading rate estimates are supported by the micro structure profile data. The extensive survey of the upper 1000m of the oxygen minimum zone (OMZ) allowed comparing our sections with several previous surveys. We found that the lowest oxygen values in the core of the OMZ have dropped at record low values below 40 μmol/kg. The preliminary findings from the trace metal work focused on Fe ligand measurements shows a slight higher excess ligand concentration in the surface (50m) for three stations. The two other stations show a slight decrease at this depth. A large number of biochemical samples were taken and were analyzed in Kiel for DNA and RNA diversity. The tracer release experiment provided an ideal environment for repeated biochemical sampling in the same water mass

OPEN COMMUNITY HEALTH: WORKSHOP REPORT

This report summarizes key outcomes from a workshop on open community health conducted at the University of Nebraska at Omaha in April 2018. Workshop members represented research and practice communities across Citizen Science, Open Source, and Wikipedia. The outcomes from the workshop include (1) comparisons among these communities, (2) how a shared understanding and assessment of open community health can be developed, and (3) a taxonomical comparison to begin a conversation between these communities that have developed disparate languages

Ocean ecosystem-based management mandates and implementation in the North Atlantic

Ecosystem-based management (EBM) necessarily requires a degree of coordination across countries that share ocean ecosystems, and among national agencies and departments that have responsibilities relating to ocean health and marine resource utilization. This requires political direction, legal input, stakeholder consultation and engagement, and complex negotiations. Currently there is a common perception that within and across national jurisdictions there is excessive legislative complexity, a relatively low level of policy coherence or alignment with regards to ocean and coastal EBM, and that more aligned legislation is needed to accelerate EBM adoption. Our Atlantic Ocean Research Alliance (AORA) task group was comprised of a small, focused and interdisciplinary mix of lawyers, social scientists, and natural scientists from Canada, the USA, and the EU. We characterized, compared, and synthesized the mandates that govern marine activities and ocean stressors relative to facilitating EBM in national and international waters of the North Atlantic, and identified formal mandates across jurisdictions and, where possible, policy and other non-regulatory mandates. We found that irrespective of the detailed requirements of legislation or policy across AORA jurisdictions, or the efficacy of their actual implementation, most of the major ocean pressures and uses posing threats to ocean sustainability have some form of coverage by national or regional legislation. The coverage is, in fact, rather comprehensive. Still, numerous impediments to effective EBM implementation arise, potentially relating to the lack of integration between agencies and departments, a lack of adequate policy alignment, and a variety of other socio-political factors. We note with concern that if challenges regarding EBM implementation exist in the North Atlantic, we can expect that in less developed regions where financial and governance capacity may be lower, that implementation of EBM could be even more challenging

Self-prioritization and perceptual matching: The effects of temporal construal.

Recent research has revealed that self-referential processing enhances perceptual judgments - the so-called self-prioritization effect. The extent and origin of this effect remains unknown, however. Noting the multifaceted nature of the self, here we hypothesized that temporal influences on self-construal (i.e., past/future-self continuity) may serve as an important determinant of stimulus prioritization. Specifically, as representations of the self increase in abstraction as a function of temporal distance (i.e., distance from now), self-prioritization may only emerge when stimuli are associated with the current self. The results of three experiments supported this prediction. Self-relevance only enhanced performance in a standard perceptual-matching task when stimuli (i.e., geometric shapes) were connected with the current self; representations of the self in the future (Expts. 1 & 2) and past (Expt. 3) failed to facilitate decision making. To identify the processes underlying task performance, data were interrogated using a hierarchical drift diffusion model (HDDM) approach. Results of these analyses revealed that self-prioritization was underpinned by a stimulus bias (i.e., rate of information uptake). Collectively, these findings elucidate when and how self-relevance influences decisional processing