Carbon and nitrogen emissions from stored manure and cropped fields in irrigated mountain oases of Oman

Little is known about gaseous carbon (C) and nitrogen (N) emissions from traditional terrace agriculture in irrigated high mountain agroecosystems of the subtropics. In an effort towards filling this knowledge gap measurements of carbon dioxide (CO_2), methane (CH_4), ammonia (NH_3) and dinitrous oxide (N_2O) were taken with a mobile photoacoustic infrared multi-gas monitor on manure-filled PE-fibre storage bags and on flood-irrigated untilled and tilled fields in three mountain oases of the northen Omani Al Jabal al Akhdar mountains. During typical 9-11 day irrigation cycles of March, August and September 2006 soil volumetric moisture contents of fields dominated by fodder wheat, barley, oats and pomegranate ranged from 46-23%. While manure incorporation after application effectively reduced gaseous N losses, prolonged storage of manure in heaps or in PE-fibre bags caused large losses of C and N. Given the large irrigation-related turnover of organic C, sustainable agricultural productivity of oasis agriculture in Oman seems to require the integration of livestock which allows for several applications of manure per year at individual rates of 20 t dry matter ha^−1.

Dieselmotor-Kraft-Wärme-Kopplungsanlagen im Kontext der Integration Erneuerbarer Energien in die Energieversorgung

In dieser Arbeit werden die sich abzeichnenden zukünftigen Möglichkeiten, Stärken und Schwächen der Kraft-Wärme-Kopplung (KWK) untersucht. Dies geschieht vor dem Hintergrund des Klimawandels, der Integration steigender Anteile Erneuerbarer Energien in die Stromerzeugung und unter Berücksichtigung der sich damit ergebenden Herausforderungen, eine sichere und nachhaltige Stromversorgung zu gestalten. Der Fokus liegt auf der Dieselmotor-KWK und der Nutzung nachwachsender Kraftstoffe. Es wird davon ausgegangen, dass der Übergang zu einer reinen Stromerzeugung aus Erneuerbaren Energiequellen in Deutschland unter erheblicher Einbindung des hohen Potentials der kostengünstigen, umweltfreundlichen, aber in der Leistung extrem fluktuierenden Windenergie erfolgen wird. Als dezentrales Integrationswerkzeug wurde die Kraft-Wärme-Kopplung mit Dieselmotoren untersucht. Sie entspricht aufgrund ihrer großen Flexibilität und ihrer hohen Wirkungsgrade mit vergleichsweise kleinen Leistungen sehr gut den Anforderungen der gleichzeitigen dezentralen Wärmenutzung. In der Dissertation werden die Randbedingungen der Dieselmotor-KWK untersucht und beschrieben. Darauf aufbauend werden unterschiedliche Modelle der Windintegration durch KWK erarbeitet und in diversen Variationen wird der Ausgleich der Stromerzeugung aus Windenergie durch KWK simuliert. Darüber hinaus werden dezentrale KWK-Anlagen hinsichtlich eines koordinierten gemeinsamen Betriebs und hinsichtlich der optimalen Auslegung für den Windenergieausgleich betrachtet. Es wird für den beschriebenen Kontext der Erneuerbaren Energien und der Kraft-Wärme-Kopplung das Thema „Umweltwirkungen“ diskutiert. Es wird dargelegt, dass die heute verwendeten Ansätze zur Bewertung der KWK zu einer Verzerrung der Ergebnisse führen. Demgegenüber wurde mit der so genannten Outputmethode eine Methode der Ökobilanzierung vorgestellt, die, im Gegensatz zu den anderen Methoden, keine verzerrenden Annahmen in die Wirkungsabschätzung aufnimmt und somit eine eindeutige und rein wissenschaftliche Auswertung bleibt. Hiermit ist die Grundlage für die Bewertung der unterschiedlichen Technologien und Szenarien sowie für die Einordnung der KWK in den Kontext der Energieerzeugung gegeben. Mit der Outputmethode wird u.a. rechnerisch bewiesen, dass die gekoppelte Strom- und Wärmeerzeugung in KWK-Anlagen tatsächlich die optimale Nutzung der regenerativen Kraftstoffe „Biogas“ und „Pflanzenöl“ im Hinblick auf Ressourceneinsatz, Treibhausgaseinsparung und Exergieerzeugung ist. Es wurde darüber hinaus die Frage untersucht woher die für die Stromerzeugung durch Dieselmotor-KWK-Anlagen notwendige Bioenergie genommen werden kann. Es ist erwiesen, dass die in Deutschland nutzbare landwirtschaftliche Fläche nur zur Deckung eines Teils der Stromerzeugung ausreichen würde. Einheimisches Biogas und nachhaltiges importiertes Pflanzenöl, das in hohem Maße auf degradierten Böden angebaut werden sollte, können die notwendige Brennstoffenergie liefern. Um im Ausland ausreichend Pflanzenöl herstellen zu können, wird eine landwirtschaftliche Fläche von 6 bis 12 Mio. ha benötigt. Das Ergebnis ist, dass ein voller Ausgleich von Windenergie-Restlast durch KWK mit Erneuerbaren Energieträgern sinnvoll und machbar ist! Dieses Wind-KWK-DSM-System sollte durch ein Stromnetz ergänzt sein, das Wasserkraftstrom für den Großteil der Regelenergieaufgaben nutzt, und das den großräumigen Ausgleich Erneuerbarer Energien in Europa und den Nachbarregionen ermöglicht.

Development and Integration of Biocontrol Products in Branched Broomrape (Phelipanche ramosa) management in Tomato

Parasitic weeds of the genera Striga, Orobanche, and Phelipanche pose a severe problem for agriculture because they are difficult to control and are highly destructive to several crops. The present work was carried out during the period October, 2009 to February, 2012 to evaluate the potential of arbuscular mycorrhizal fungi (AMF) to suppress P. ramosa on tomatoes and to investigate the effects of air-dried powder and aqueous extracts from Euphorbia hirta on germination and haustorium initiation in Phelipanche ramosa. The work was divided into three parts: a survey of the indigenous mycorrhizal flora in Sudan, second, laboratory and greenhouse experiments (conducted in Germany and Sudan) to construct a base for the third part, which was a field trial in Sudan. A survey was performed in 2009 in the White Nile state, Sudan to assess AMF spore densities and root colonization in nine fields planted with 13 different important agricultural crops. In addition, an attempt was made to study the relationship between soil physico-chemical properties and AMF spore density, colonization rate, species richness and other diversity indices. The mean percentage of AMF colonization was 34%, ranging from 19-50%. The spore densities (expressed as per 100 g dry soil) retrieved from the rhizosphere of different crops were relatively high, varying from 344 to 1222 with a mean of 798. There was no correlation between spore densities in soil and root colonization percentage. A total of 45 morphologically classifiable species representing ten genera of AMF were detected with no correlation between the number of species found in a soil sample and the spore density. The most abundant genus was Glomus (20 species). The AMF diversity expressed by the Shannon–Weaver index was highest in sorghum (H\= 2.27) and Jews mallow (H\= 2.13) and lowest in alfalfa (H\= 1.4). With respect to crop species, the genera Glomus and Entrophospora were encountered in almost all crops, except for Entrophospora in alfalfa. Kuklospora was found only in sugarcane and sorghum. The genus Ambispora was recovered only in mint and okra, while mint and onion were the only species on which no Acaulospora was found. The hierarchical cluster analysis based on the similarity among AMF communities with respect to crop species overall showed that species compositions were relatively similar with the highest dissimilarity of about 25% separating three of the mango samples and the four sorghum samples from all other samples. Laboratory experiments studied the influence of root and stem exudates of three tomato varieties infected by three different Glomus species on germination of P. ramosa. Root exudates were collected 21or 42 days after transplanting (DAT) and stem exudates 42 DAT and tested for their effects on germination of P. ramosa seeds in vitro. The tomato varieties studied did not have an effect on either mycorrhizal colonization or Phelipanche germination. Germination in response to exudates from 42 day old mycorrhizal plants was significantly reduced in comparison to non-mycorrhizal controls. Germination of P. ramosa in response to root exudates from 21 day old plants was consistently higher than for 42 day-old plants (F=121.6; P<.0001). Stem diffusates from non-mycorrhizal plants invariably elicited higher germination than diffusates from the corresponding mycorrhizal ones and differences were mostly statistically significant. A series of laboratory experiments was undertaken to investigate the effects of aqueous extracts from Euphorbia hirta on germination, radicle elongation, and haustorium initiation in P. ramosa. P. ramosa seeds conditioned in water and subsequently treated with diluted E. hirta extract (10-25% v/v) displayed considerable germination (47-62%). Increasing extract concentration to 50% or more reduced germination in response to the synthetic germination stimulants GR24 and Nijmegen-1 in a concentration dependent manner. P. ramosa germlings treated with diluted Euphorbia extract (10-75 % v/v) displayed haustorium initiation comparable to 2, 5-Dimethoxy-p-benzoquinon (DMBQ) at 20 µM. Euphorbia extract applied during conditioning reduced haustorium initiation in a concentration dependent manner. E. hirta extract or air-dried powder, applied to soil, induced considerable P. ramosa germination. Pot experiments were undertaken in a glasshouse at the University of Kassel, Germany, to investigate the effects of P. ramosa seed bank on tomato growth parameters. Different Phelipanche seed banks were established by mixing the parasite seeds (0 - 32 mg) with the potting medium in each pot. P. ramosa reduced all tomato growth parameters measured and the reduction progressively increased with seed bank. Root and total dry matter accumulation per tomato plant were most affected. P. ramosa emergence, number of tubercles, and tubercle dry weight increased with the seed bank and were, invariably, maximal with the highest seed bank. Another objective was to determine if different AM fungi differ in their effects on the colonization of tomatoes with P. ramosa and the performance of P. ramosa after colonization. Three AMF species viz. GIomus intraradices, Glomus mosseae and Glomus Sprint® were used in this study. For the infection, P. ramosa seeds (8 mg) were mixed with the top 5 cm soil in each pot. No mycorrhizal colonization was detected in un-inoculated control plants. P. ramosa infested, mycorrhiza inoculated tomato plants had significantly lower AMF colonization compared to plants not infested with P. ramosa. Inoculation with G. intraradices, G. mosseae and Glomus Sprint® reduced the number of emerged P. ramosa plants by 29.3, 45.3 and 62.7% and the number of tubercles by 22.2, 42 and 56.8%, respectively. Mycorrhizal root colonization was positively correlated with number of branches and total dry matter of tomatoes. Field experiments on tomato undertaken in 2010/12 were only partially successful because of insect infestations which resulted in the complete destruction of the second run of the experiment. The effects of the inoculation with AMF, the addition of 10 t ha-1 filter mud (FM), an organic residues from sugar processing and 36 or 72 kg N ha-1 on the infestation of tomatoes with P. ramosa were assessed. In un-inoculated control plants, AMF colonization ranged between 13.4 to 22.1% with no significant differences among FM and N treatments. Adding AMF or FM resulted in a significant increase of branching in the tomato plants with no additive effects. Dry weights were slightly increased through FM application when no N was applied and significantly at 36 kg N ha-1. There was no effect of FM on the time until the first Phelipanche emerged while AMF and N application interacted. Especially AMF inoculation resulted in a tendency to delayed P. ramosa emergence. The marketable yield was extremely low due to the strong fruit infestation with insects mainly whitefly Bemisia tabaci and tomato leaf miner (Tuta absoluta). Tomatoes inoculated with varied mycorrhiza species displayed different response to the insect infestation, as G. intraradices significantly reduced the infestation, while G. mosseae elicited higher insect infestation. The results of the present thesis indicate that there may be a potential of developing management strategies for P. ramosa targeting the pre-attachment stage namely germination and haustorial initiation using plant extracts. However, ways of practical use need to be developed. If such treatments can be combined with AMF inoculation also needs to be investigated. Overall, it will require a systematic approach to develop management tools that are easily applicable and affordable to Sudanese farmers. It is well-known that proper agronomical practices such as the design of an optimum crop rotation in cropping systems, reduced tillage, promotion of cover crops, the introduction of multi-microbial inoculants, and maintenance of proper phosphorus levels are advantageous if the mycorrhiza protection method is exploited against Phelipanche ramosa infestation. Without the knowledge about the biology of the parasitic weeds by the farmers and basic preventive measures such as hygiene and seed quality control no control strategy will be successful, however.

Von der Integration ausländischer Studierender zur Hochschule als transkultureller Lernort

Auf die Herausforderungen der Internationalisierung antworten die deutschen Hochschulen mit verstärkten Bemühungen zur Integration ausländischer Studierender. Damit ist der sozialwissenschaftlich nicht unumstrittene Integrationsdiskurs der Ausländerpolitik auf dem Campus angekommen. Gleichzeitig stehen transkulturelle Begriffe immer mehr im Fokus der aktuellen sozial-, kultur- und erziehungswissenschaftlichen Diskurse. Auf der Grundlage von Erfahrungen aus einem PROFIN-Projekt an der Universität Kassel setzt sich der Artikel damit auseinander, welche Potentiale eine Internationalisierung aus der Perspektive dieser Diskurse für eine innovative Entwicklung von Lehre und Forschung im internationalen Kontext bietet.

Integration der strategischen Planung in die Haushaltsplanung einer Kommune

Eine effektive, effiziente und wirkungsorientierte kommunalpolitische Arbeit stellt hohe Anforderungen an Politik und Verwaltung. Trotz zahlreicher erfolgsversprechender Ansätze ist der aktuelle Status quo ernüchternd. Schwerpunkt der Dissertation ist deshalb die Entwicklung eines praxistauglichen Konzeptes zur Integration der strategischen Planung in die Haushaltsplanung einer Kommune mit dem Ziel einer nachhaltigen Verbesserung der strategischen Steuerung. Eine ergänzende ökonomische Funktionsanalyse von beteiligten Rechtsfiguren erweitert dabei die klassisch wirtschaftstheoretische Betrachtungsweise um sozialwissenschaftliche Aspekte, die im Zusammenspiel von Institutionen eine wichtige Rolle spielen. Der konzipierte Ansatz kommt, durch die Fokussierung auf das öffentliche Interesse, einem partizipativen und transparenten Idealbild von Steuerung im kommunalen Bereich auf der Basis der New Public Management Bewegung sehr nahe und könnte helfen der verstärkt festzustellenden Politikverdrossenheit entgegen zu wirken.

Molecular Beam Epitaxial Growth of III-V Semiconductor Nanostructures on Silicon Substrates

The main focus and concerns of this PhD thesis is the growth of III-V semiconductor nanostructures (Quantum dots (QDs) and quantum dashes) on silicon substrates using molecular beam epitaxy (MBE) technique. The investigation of influence of the major growth parameters on their basic properties (density, geometry, composition, size etc.) and the systematic characterization of their structural and optical properties are the core of the research work. The monolithic integration of III-V optoelectronic devices with silicon electronic circuits could bring enormous prospect for the existing semiconductor technology. Our challenging approach is to combine the superior passive optical properties of silicon with the superior optical emission properties of III-V material by reducing the amount of III-V materials to the very limit of the active region. Different heteroepitaxial integration approaches have been investigated to overcome the materials issues between III-V and Si. However, this include the self-assembled growth of InAs and InGaAs QDs in silicon and GaAx matrices directly on flat silicon substrate, sitecontrolled growth of (GaAs/In0,15Ga0,85As/GaAs) QDs on pre-patterned Si substrate and the direct growth of GaP on Si using migration enhanced epitaxy (MEE) and MBE growth modes. An efficient ex-situ-buffered HF (BHF) and in-situ surface cleaning sequence based on atomic hydrogen (AH) cleaning at 500 °C combined with thermal oxide desorption within a temperature range of 700-900 °C has been established. The removal of oxide desorption was confirmed by semicircular streaky reflection high energy electron diffraction (RHEED) patterns indicating a 2D smooth surface construction prior to the MBE growth. The evolution of size, density and shape of the QDs are ex-situ characterized by atomic-force microscopy (AFM) and transmission electron microscopy (TEM). The InAs QDs density is strongly increased from 108 to 1011 cm-2 at V/III ratios in the range of 15-35 (beam equivalent pressure values). InAs QD formations are not observed at temperatures of 500 °C and above. Growth experiments on (111) substrates show orientation dependent QD formation behaviour. A significant shape and size transition with elongated InAs quantum dots and dashes has been observed on (111) orientation and at higher Indium-growth rate of 0.3 ML/s. The 2D strain mapping derived from high-resolution TEM of InAs QDs embedded in silicon matrix confirmed semi-coherent and fully relaxed QDs embedded in defectfree silicon matrix. The strain relaxation is released by dislocation loops exclusively localized along the InAs/Si interfaces and partial dislocations with stacking faults inside the InAs clusters. The site controlled growth of GaAs/In0,15Ga0,85As/GaAs nanostructures has been demonstrated for the first time with 1 μm spacing and very low nominal deposition thicknesses, directly on pre-patterned Si without the use of SiO2 mask. Thin planar GaP layer was successfully grown through migration enhanced epitaxy (MEE) to initiate a planar GaP wetting layer at the polar/non-polar interface, which work as a virtual GaP substrate, for the GaP-MBE subsequently growth on the GaP-MEE layer with total thickness of 50 nm. The best root mean square (RMS) roughness value was as good as 1.3 nm. However, these results are highly encouraging for the realization of III-V optical devices on silicon for potential applications.