Die Wirkung von Düngerart und Düngermenge auf die Partitionierung von Kohlenstoff und Stickstoff in Pools mit unterschiedlichem Umsatz

Type and rate of fertilizer influence the level of organic carbon and total nitrogen in the soil markedly, but the effect on different pools is open to question. Soil samples were taken from a sandy Cambisol at Darmstadt, Germany, after 27 years of different fertilization treatments. The six treatments were: straw incorporation plus application of mineral fertilizer (MSI) and application of farmyard manure (FYM) each at high (140 – 150 kg N ha-1 year-1), medium (100 kg N ha-1 year-1) and low (50 – 60 kg N ha-1 year-1) rates. After 266 days of incubation (10°C, 50% water-filled pore space) mineralization of C (1130 – 1820 kg ha-1) and N (90 – 125 kg ha-1) depended on the rate and not on the type of fertilizer. Very labile and labile pools were obtained by fitting a two-pool model on the mineralization data. The very labile pool (turnover: 17 days, C/N ratio: 23) was unaffected by treatments. Storage of C (1.8 – 3.2 t ha-1) in the labile pool (turnover 462 days, C/N ratio: 22) increased significantly with the rate of fertilizer. The size of the intermediate pool was significantly higher in FYM (15 -18 t ha-1) than in MSI treatments (12- 14 t ha-1). A passive pool, obtained by oxidation with Na2S2O8, was independent of treatments. Our study shows that labile and intermediate pools were affected differently by fertilization

Comportamento de cultivares no ensaio Sul-Rio-Grandense de sorgo, para corte/pastejo, Capão do Leão, RS. 2004/2005.

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Processing and characterization of glass-ceramic foams belonging to the Li2O-ZrO2-Al2O3-SiO2 (LZSA) system produced by gelcasting

In this work the viscosimetry technique was used to evaluate the rheological characteristics of ceramic suspensions prepared with a LZSA (Li2O-ZrO2-SiO2-Al2O3) glass. From the rheological characterization it was possible to establish optimized conditions of solid fraction, dispersant, organic monomers and foaming agent for the production of glass-ceramic foams by gelcasting. The resulting foams were subjected to heattreatments at 200-500ºC/60 min, for degradation of organics and at 950ºC/60 min for sintering and crystallization. With the obtained porous ceramic bodies linear thermal shrinkage, apparent density and mechanical strength measurements as well as microstructural analysis were performed. The adaptation of the rheological characteristics of the LZSA parent glass powder with the gelcasting processing technique allowed the production of ceramic foams with high open and interconnected porosity (>90%) with good thermal stability and with mechanical strength suitable for the production of porous ceramics.Neste trabalho, a técnica de viscosimetria foi utilizada para avaliar as características reológicas de suspensões preparadas com precursor vitrocerâmico do sistema LZSA (Li2O-ZrO2-SiO2-Al2O3). A partir da caracterização reológica, foi possível estabelecer condições composicionais adequadas de fração de sólidos, dispersante e monômeros orgânicos. A quantidade de agente espumante para produção de espumas vitrocerâmicas por gelcasting foi determinada pela variação volumétrica após agitação. As espumas resultantes foram submetidas a tratamentos térmicos no intervalo de temperatura compreendido entre 200 e 500ºC/60 min, para degradação da matéria orgânica e a 950ºC/60 min para sinterização e cristalização. Com os corpos cerâmicos porosos foram realizadas medidas de retração térmica, densidade aparente, análise microestrutural e resistência mecânica. A adequação das características reológicas do precursor LZSA por gelcasting permitiu a produção de espumas com elevada porosidade (> 90%) aberta e interconectada com boa estabilidade térmica e com resistência mecânica compatível com cerâmicas [email protected]@[email protected]@emc.ufsc.brUniversidade Federal de Santa Catarina Departamento de Engenharia Mecânica Programa de Pós-Graduação em Ciência e Engenharia de MateriaisCentro Universitário Barriga Verde - UNIBAVEUniversidade Federal de São Paulo (UNIFESP) Departamento de Ciência e TecnologiaUNIFESP, Depto. de Ciência e TecnologiaSciEL

Neonicotinoid Insecticide Imidacloprid Causes Outbreaks of Spider Mites on Elm Trees in Urban Landscapes

BACKGROUND: Attempts to eradicate alien arthropods often require pesticide applications. An effort to remove an alien beetle from Central Park in New York City, USA, resulted in widespread treatments of trees with the neonicotinoid insecticide imidacloprid. Imidacloprid's systemic activity and mode of entry via roots or trunk injections reduce risk of environmental contamination and limit exposure of non-target organisms to pesticide residues. However, unexpected outbreaks of a formerly innocuous herbivore, Tetranychus schoenei (Acari: Tetranychidae), followed imidacloprid applications to elms in Central Park. This undesirable outcome necessitated an assessment of imidacloprid's impact on communities of arthropods, its effects on predators, and enhancement of the performance of T. schoenei. METHODOLOGY/PRINCIPAL FINDINGS: By sampling arthropods in elm canopies over three years in two locations, we document changes in the structure of communities following applications of imidacloprid. Differences in community structure were mostly attributable to increases in the abundance of T. schoenei on elms treated with imidacloprid. In laboratory experiments, predators of T. schoenei were poisoned through ingestion of prey exposed to imidacloprid. Imidacloprid's proclivity to elevate fecundity of T. schoenei also contributed to their elevated densities on treated elms. CONCLUSIONS/SIGNIFICANCE: This is the first study to report the effects of pesticide applications on the arthropod communities in urban landscapes and demonstrate that imidacloprid increases spider mite fecundity through a plant-mediated mechanism. Laboratory experiments provide evidence that imidacloprid debilitates insect predators of spider mites suggesting that relaxation of top-down regulation combined with enhanced reproduction promoted a non-target herbivore to pest status. With global commerce accelerating the incidence of arthropod invasions, prophylactic applications of pesticides play a major role in eradication attempts. Widespread use of neonicotinoid insecticides, however, can disrupt ecosystems tipping the ecological balance in favor of herbivores and creating pest outbreaks

Ferrugem da soja: prevenção através de cultivares resistentes.

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Bilan et perspectives de la Recherche en Agriculture Bio-dynamique

L’Agriculture Biodynamique (BD) a été l’objet de nombreux efforts de recherches durant les dernières décennies, bien qu’une partie de la communauté scientifique regarde les méthodes biodynamiques avec scepticisme et les considère comme dogmatiques. Néanmoins, comme cela est montré dans cet article de synthèse, une part non négligeable des résultats présentés dans des revues scientifiques à comité de lecture et issus d’expérimentations contrôlées de plein champ, ou d’étude de cas, montrent des effets des préparations biodynamiques sur le rendement, la qualité du sol et la biodiversité. De plus, les préparations biodynamiques ont un impact environnemental positif en termes d’utilisation et d’efficacité énergétique. Cependant, le mode d’action mécanique des préparations biodynamique est toujours en cours d’investigation en sciences naturelles. Par ailleurs, les méthodes d’évaluations de la qualité basées sur des approches globales (holistiques) sont de plus en plus étudiées et reconnues. L’agriculture BD s’efforce également, comme cela est montré dans plusieurs publications, d’influencer positivement le paysage culturel. La synthèse des données montre le besoin de poursuivre les recherches dans le domaine de la qualité des aliments, de la sécurité alimentaire, des performances environnementales (par ex. l’empreinte écologique), et sur l’influences des pratiques BD sur les animaux d’élevage

Ocorrência de fungos em sementes de sorgo, milho, soja e trigo.

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