Thesis (Ph. D.)--Washington State University, August 2009. / Title from PDF title page (viewed on Aug. 28, 2009). "Department of Crop and Soil Sciences." Includes bibliographical references.

Thesis (doctoral)--Swedish University of Agricultural Sciences, 2000. / Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1969. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--University of North Carolina Wilmington, 2007. / Includes bibliographical references (leaves: 120-121)

Dissertation (PhD (Agric))--University of Stellenbosch, 2005. / Bibliography. Also available via the Internet.

Thesis (Ph. D.)--Lehigh University, 2006. / Includes vita. Includes bibliographical references (leaves 187-192).

Thesis (M.S.) University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (June 26, 2007) Includes bibliographical references.

Biogeochemical processes in the marine biosphere are important in global element cycling and greatly influence the gas composition of the Earth’s atmosphere. The nitrogen cycle is a key component of marine biogeochemical cycles. Nitrogen is an essential constituent of living organisms, but bioavailable nitrogen is often short in supply thus limiting primary production. The largest input of nitrogen to the marine environment is by N2-fixation, the transformation of inert N2 gas into bioavailable ammonium by a distinct group of microbes. Hence, N2-fixation bypasses nitrogen limitation and stimulates productivity in oligotrophic regions of the marine biosphere. Extensive blooms of N2-fixing cyanobacteria occur regularly during summer in the Baltic Sea. N2-fixation during these blooms adds several hundred kilotons of new nitrogen into the Baltic Proper, which is similar in magnitude to the annual nitrogen load by riverine discharge and more than twice the atmospheric nitrogen deposition in this area. N2-fixing cyanobacteria are therefore a critical constituent of nitrogen cycling in the Baltic Sea. In this thesis N2 fixation of common cyanobacteria in the Baltic Sea and the direct fate of newly fixed nitrogen in otherwise nitrogen-impoverished waters were investigated. Initially, the commonly used 15N-stable isotope assay for N2-fixation measurements was evaluated and optimized in terms of reliability and practicality (Paper I), and later applied for N2-fixation assessments (Paper II–IV). N2 fixation in surface waters of the Baltic Sea was restricted to large filamentous heterocystous cyanobacteria (Aphanizomenon sp., Nodularia spumigena, Dolichospermum spp.) and absent in smaller filamentous cyanobacteria such as Pseudanabaena sp., and unicellular and colonial picocyanobacteria (Paper II-III). Most of the N2-fixation in the Northern Baltic Proper was contributed by Aphanizomenon sp. due to its high abundance throughout the summer and similar rates of specific N2-fixation as Dolichospermum spp. and N. spumigena. Specific N2 fixation was substantially higher near the coast than in an offshore region (Paper II). Half of the fixed nitrogen was released as ammonium at the site near the coast and taken up by non-N2-fixing organisms including phototrophic and heterotrophic, prokaryotic and eukaryotic planktonic organisms. Newly fixed nitrogen was thereby rapidly turned-over in the nitrogen-depleted waters (Paper III). In colonies of N. spumigena even the potential for a complete nitrogen cycle condensed to a microcosm of a few millimeters could be demonstrated (Paper IV). Cyanobacterial colonies can therefore be hot-spots of nitrogen transformation processes potentially including nitrogen gain, recycling and loss processes. In conclusion, blooms of cyanobacteria are instrumental for productivity and CO2 sequestration in the Baltic Sea. These findings advance our understanding of biogeochemical cycles and ecosystem functioning in relation to cyanobacterial blooms in the Baltic Sea with relevance for both ecosystem-based management in the Baltic Sea, and N2-fixation and nitrogen cycling in the global ocean. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 2: Manuscript.</p>

Made available in DSpace on 2014-06-11T19:27:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-01-12Bitstream added on 2014-06-13T20:17:00Z : No. of bitstreams: 1 campana_m_me_botfmvz.pdf: 694345 bytes, checksum: 5b95a0f43e56990d64086b8a724378b9 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Universidade Estadual Paulista (UNESP) / Com objetivo de validar o uso no campo do coletor de espuma com ácido e politetrafluoroetileno que capta amônia volatilizada e quantificar essa perda oriunda de fontes e formas de aplicação de nitrogênio (N) em pastagens, realizou-se 2 experimentos. No experimento 1, para avaliação do coletor, utilizou-se fatorial 2 x 2 - doses de N (50 e 100 kg/ha) e coletores de amônia (coletor semi-aberto e absorvedor de espuma com ácido e politretafluoroetileno). O período experimental foi de 22 dias. No experimento 2 utilizou-se delineamento de blocos ao acaso e os tratamentos foram: uréia; Super N®; uréia + 12,5% de zeólita; uréia + 25% de zeólita; uréia + 50% de zeólita; uréia em pulverização foliar; 75% de uréia + 25% de sulfato de amônio; nitrato de amônio e sem N (testemunha). A avaliação das perdas por volatilização de amônia ocorreu em 3 épocas. No verão/07 e inverno/07 utilizou-se dose de 50 kg/ha de N para adubos sólidos e 15 kg/ha de N para pulverização foliar e para o verão/08 as doses foram duplicadas. As perdas diárias de amônia foram avaliadas em onze amostragens a cada dois dias para ambos os experimentos. Para o experimento 1, não houve diferença entre os coletores na perda acumulada e diária de amônia com a dose de 50 kg/ha de N. Entretanto, na dose de 100 kg/ha de N o coletor semi-aberto captou o maior pico de volatilização diária e maior acúmulo de amônia. No experimento 2 as menores perdas por volatilização foram detectadas para nitrato de amônio aplicado a lanço e uréia via pulverização foliar. Dessa forma poderia ocorrer melhor uso do fertilizante pela planta refletindo em aumento na produção e qualidade da forragem. / With the objective of validating the field use of the foam collector with acid and polytetrafluorethylene, which captures volatilized ammonia and quantify this loss when using sources and application forms of nitrogen (N) in pastures, 2 experiments were realized. In the experiment 1, to evaluate the collector a 2 x 2 factorial – N doses (50 and 100 kg/ha) and ammonia collectors (semi-open collector and foam absorber with acid and polytetrafluorethylene). The experimental period was 22 days. In the experiment 2, the experimental design was a randomized block design and the treatments were: urea; Super N®; urea + 12,5% of zeolite; urea + 25% of zeolite; urea + 50% of zeolite; urea leaf spraying, 75% of urea + 25% of ammonium sulfate, ammonium nitrate, and without nitrogen (control). The evaluation of the volatilization losses occurred in 3 periods. On summer/07 and winter/2007 a 50 kg/ha of N dose for solid fertilizers was used and a 15 kg/ha N dose for leaf spraying and on summer/2008 the doses were doubled. The daily losses of ammonia were evaluated in eleven samplings every two days for both experiments. In the experiment 1, there was no difference between the collectors in the accumulated and daily loss in the dose of 50kg/ha of N. However, with the dose of 100 kg/ha of N the semi-open collector showed the highest peak of daily volatilization and accumulated the highest volatilization loss. In the experiment 2, the lowest volatilization losses were detected for ammonium nitrate in soil application and urea in leaf spraying application. So, in this cases might happen the better use of the fertilizer by the plant, reflecting in the increase of the forage production and quality.

Made available in DSpace on 2014-06-11T19:28:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-06-26Bitstream added on 2014-06-13T19:16:25Z : No. of bitstreams: 1 silva_jdr_me_jabo.pdf: 254971 bytes, checksum: 5a4a9ab65bae7e34ba57a261dc3dbbc0 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A caracterização e quantificação das frações nitrogenadas presentes no caldo de diferentes cultivares de cana-de-açúcar pode facilitar a identificação da principal aptidão industrial da mesma para a produção de açúcar (baixos teores de nitrogênio), ou de etanol e cachaça (altos teores de nitrogênio). A hipótese deste trabalho é que diferentes cultivares precoces, médios e tardios possam produzir caldos com diferentes teores de nitrogênio e, portanto serem utilizados com maior desempenho nos processos de fermentação ou na produção de açúcar. Este trabalho tem como objetivo quantificar as frações nitrogenadas (amoniacal, protéica, total, não-protéica e amínica) em caldos de dezoito cultivares de cana-de-açúcar em soqueiras de segundo corte. O delineamento experimental utilizado foi o inteiramente casualizado com parcelas subdividas e três repetições. Foram avaliados dezoito cultivares com três ciclos de maturação, em 5 épocas (0, 28, 69, 112 e 154 dias) durante o ano agrícola 2010/2011. No destilado, obtido a partir do caldo procedeu-se a determinação do nitrogênio amoniacal de acordo com o método de micro-Kjeldahl. Os teores de nitrogênio total e nitrogênio não-protéico, determinado em caldo desproteinizado com hidróxido de bário a 0,3N e sulfato de zinco a 5%, também foram determinados pelo método de micro-Kjeldahl. Os teores de nitrogênio protéico e amínico foram estimados por meio de cálculos. Os resultados obtidos foram submetidos à análise de variância (teste F) que quando significativa, as médias foram comparadas pelo teste de Tukey, ao nível de 5% de probabilidade. O cultivar SP91-1049 obteve os maiores valores para as frações de nitrogênio amoniacal, total e protéico, além de maiores teores na interação para as frações amoniacal, protéica e total ao longo das... / The characterization and quantification of nitrogen fractions present in the juice of different varieties of sugar cane can help identify the main industry of the same ability to produce sugar (low levels of nitrogen), or ethanol and cachaça (high levels of nitrogen). The hypothesis is that different early cultivars, middle and late to produce stocks with different levels of nitrogen and therefore be used with higher performance in fermentation processes or the production of sugar. This study aims to quantify the nitrogen fractions (ammonium, protein, total non-protein and amine) in broths eighteen cultivars of sugar cane stumps on the second cut. The experimental design was completely randomized design with subdivided plots and three replications. Eighteen cultivars were evaluated with three cycles of maturation in 5 times (0, 28, 69, 112 and 154 days) during the 2010/2011 agricultural year. The distillate obtained from the broth made the determination of ammonia according to the micro-Kjeldahl method. The levels of total nitrogen and non-protein nitrogen determined in broth deproteinized with barium hydroxide and 0.3 N zinc sulfate 5%, were also determined by micro-Kjeldahl method. The levels of protein and amino nitrogen were estimated by calculations. The results were submitted to analysis of variance (F test) when significant, means were compared by Tukey test at 5% probability. The cultivar SP91-1049 achieved the highest values for the fractions of ammonia nitrogen, total protein and, in addition to higher levels in the interaction for the fractions ammonia, and total protein through the ages. The results indicate that the cultivars studied showed significant differences in levels of nitrogen fractions and the collection times are much greater importance in these levels. The cultivar with a mean cycle of maturation... (Complete abstract click electronic access below)