1,720,958 research outputs found
Biochar additions to agricultural soils: impacts on the behavior of mobile herbicides
Get PDFMobile herbicides have a high potential for contaminating groundwater. Biochar have been proposed as an alternative to retain herbicides and modify soil microbial community, thus, limiting the transport of herbicides and other contaminants in soil and water sources. The objective of this research was to evaluate the effect biochar amendments on sorption-desorption and mineralization of mobile herbicides in agricultural soils. In chapter one, sorption-desorption were evaluated using the batch equilibrium method at five concentrations of hexazinone, metribuzin and quinclorac. Soil was amended with eucalyptus (Eucalyptus grandis), rice hull (Oryza sativa), and native bamboo (Merostachys skorvotzii) biochar at rate of 0 (control – unamended) and 1% (w w-1), corresponding to 0 and 12 t ha-1, respectively. The highest sorption in unamended soil followed the decreasing order of herbicides: quinclorac (65.9 %) > metribuzin (21.4 %) > hexazinone (16.0 %). Native bamboo biochar provided the highest sorption in comparison to rice hull and eucalyptus biochar amended soils for the three herbicides. The highest desorption in unamended soil followed the decreasing order of herbicides: metribuzin (18.35 %) > hexazinone (15.9 %) > quinclorac (15.1 %). Addition of native bamboo biochar provided the lowest desorption among the biochar amendments on the three herbicides. In chapter two, sorption and desorption were evaluated using the batch equilibrium method at five concentrations of metribuzin. Three soils were amended with grape wood (Vitis vinifera L.) and loblolly pine (Pinus taeda) biochars at rate of 0 (control – unamended) and 5% (w w-1), corresponding to 0 and 60 t ha-1, respectively. Mineralization of 14C-metribuzin was performed in biometer flasks at a rate of 4 mg·kg−1 (target concentration). The 14CO2-metribuzin released from mineralization was trapped in 0.4 M sodium hydroxide solution (NaOH) analyzed at each sampling time (1, 3, 7, 14, 21, 28, 35 and 42 days). Sorption of metribuzin on the three unamended soils followed the decreasing order: drummer (61.3 %) > oakville (24.56 %) > ipava (22.35 %). Grape wood biochar (82.6 – 83.3 %) showed the highest amount sorbed compared to loblolly pine biochar (43.9 – 68.4 %) in all the three soils. Ipava soil provided the highest amount of desorbed metribuzin among the unamended soils in both, first (40.52%) and second (57.97%) desorption step. Loblolly pine biochar provided the lowest amount desorbed on first (16.4 – 29.5 %) and second (24.7 – 42.5 %) desorption steps between the two biochars in all the three soils. The two consecutive steps of metribuzin desorption showed that more than 65% of the sorbed metribuzin was retained in the soils amended with grape wood biochar. Metribuzin mineralization in drummer, ipava and okaville soil was low in comparison to the initial concentration applied. The addition of grape wood and loblolly biochar decreased mineralization and increased the non-extractable amount of metribuzin, but this effect was only observed for some soils. As conclusion, the addition of biochar is a good alternative to increase the sorption and avoid the transport of mobile herbicides in agricultural soils.Herbicidas móveis têm um alto potencial de contaminação das águas subterrâneas. Assim, o biocarvão tem sido proposto como alternativa para reter herbicidas e modificar a comunidade microbiana do solo, limitando o transporte de herbicidas e outros contaminantes no solo e em fontes de água. O objetivo desta pesquisa foi avaliar o efeito das alterações do biocarvão na sorção-dessorção e mineralização de herbicidas móveis em solos agricultáveis. No capítulo um, a sorção-dessorção foram avaliadas usando o método de equilíbrio de batelada com cinco concentrações de hexazinone, metribuzin e quinclorac. O solo foi alterado com biocarvão de eucalipto (Eucalyptus grandis), casca de arroz (Oryza sativa) e bambu nativo (Merostachys skorvotzii) na proporção de 0 (controle - sem alterações) e 1% (m m-1), correspondentes a 0 e 12 t ha-1, respectivamente. A maior sorção em solo não alterado seguiu a ordem decrescente de herbicidas: quinclorac (65,9%)> metribuzin (21,4%)> hexazinone (16,0%). O biocarvão de bambu nativo proporcionou a maior sorção comparado aos solos alterados com biocarvão de casca de arroz e eucalipto para os três herbicidas. A maior dessorção nos solos não alterados seguiu a ordem decrescente de herbicidas: metribuzin (18,35%)> hexazinone (15,9%)> quinclorac (15,1%). A adição de biocarvão de bambu nativo proporcionou a menor dessorção entre as modificações do solo para os três herbicidas. No capítulo dois, a sorção e dessorção foram avaliadas usando o método de equilíbrio de batelada com cinco concentrações do metribuzin. Três solos foram alterados com biocarvão de madeira de uva (Vitis vinifera L.) e pinheiro loblolly (Pinus taeda L.) na concentração de 0 (controle - sem alterações) e 5% (m m-1), correspondentes a 0 e 60 t ha-1, respectivamente. A mineralização da 14C-metribuzin foi realizada em frascos biométricos a uma concentração de 4 mg kg-1 (concentração alvo). O 14CO2-metribuzin liberado da mineralização foi aprisionado em solução de hidróxido de sódio a 0,4 M (NaOH) analisada em cada tempo de amostragem (1, 3, 7, 14, 21, 28, 35 e 42 dias). A sorção do metribuzin nos três solos não alterados seguiu a ordem decrescente: drummer (61,3%)> oakville (24,56%)> ipava (22,35%). O biocarvão de madeira de uva (82,6 - 83,3%) apresentou a maior quantidade sorvida em comparação com o biocarvão de pinheiro loblolly (43,9 - 68,4%) nos três solos. O solo ipava forneceu a maior quantidade de metribuzin dessorvida entre os solos não alterados, tanto na primeira (40,52%) quanto na segunda (57,97%) etapas de dessorção. O biocarvão de pinheiro loblolly forneceu a menor quantidade dessorvida na primeira (16,4 - 29,5%) e segunda (24,7 - 42,5%) etapa de dessorção entre os dois biocarvões nos três solos. As duas etapas consecutivas de dessorção do metribuzin mostraram que mais de 65% do metribuzin sorvido foram retidos nos solos alterados com biocarvão de madeira de uva. A mineralização do metribuzin nos solos drummer, ipava e okaville foi baixa em relação à concentração de herbicida aplicada. A adição de biocarvão de madeira de uva e pinheiro loblolly reduziu a mineralização e aumentou a quantidade de metribuzin não extraível, mas esse efeito foi observado apenas em alguns solos. Como conclusão, a adição de biocarvão é uma boa alternativa para aumentar a sorção e evitar o transporte de herbicidas móveis em solos agrícolas.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPE
Association of Fusarium solani, Macrophomina phaseolina and Rhizoctonia solani causing root rot in muskmelon under effect of green manure
No full textThe occurrence of root diseases is one of the main reasons of yield loss in melon crop, especially the pathogens that causes root and collar rot, as the fungi Fusarium solani (Mart.) Sacc., Macrophomina phaseolina (Tassi) Gold. and Rhizoctonia solani Kuhn, being observed in muskmelon either alone or associated. The use of crop residues and plant materil, besides the improvement in the physical properties of the soil, also favors microbial activity of the species presents in this environment and affects negatively onpathogens population. Therefore, the objective of this work was to evaluate the associations of F. solani, M. phaseolina and R. solani in the incidence and severity of root rot and fresh and dry weight of muskmelon and verify the effect of green manure in root rot caused by these pathogens alone or associated. The experiment was conducted in two stages, in a greenhouse. The first stage evaluated the association of F. solani, M. phaseolina and R. solani causing root rot in melon, using a randomized block design with 8 treatments (F. solani; M. phaseolina, R. solani, F. solani + M. phaseolina, F. solani + R. solani; M. phaseolina + R. solani, F. solani + M. phaseolina + R. solani; non-infested soil) and 8 repetitions with experimental unit of one pot (3.5 L) with 2 plants. The characteristics evaluated were the incidence of root rot in melon plants at the end of the cycle; disease severity based on a scale notes, and the fresh and dry weight of muskmelon. At the second stage, evaluated the effects of green manure in the association of these pathogens in muskmelon, which was conducted one experiment with Jack beans (Canavalia ensiformis L. DC) and another with Pearl millet (Pennisetum glaucum (L.) R. BR.). The experiments were performed simultaneously in a randomized block design with 8 x 4 factorial {8 types of fungi / association (M. phaseolina, R. solani, F. solani, M. phaseolina + R. solani; M. phaseolina + F. solani, R. solani + F. solani; M. phaseolina + R. solani + F. solani; non-infested soil), 4 forms of management [incorporated, in coverage, polyethylene film (mulching) and without managment]} and 4 repetitions. The characteristics evaluated were the incidence of root rot of melon plants at the end of the cycle, and the fresh and dry weight of muskmelon. The results of disease incidence were submitted to the non-parametric test of Kruskal-Wallis and the fresh and dry weight of muskmelon were analyzed by the Scott-Knott test, both with significance level of 5% of probability (α = 0.05%). At stage 1, the treatment with the three pathogens F. solani, M. phaseolina and R. solani associated resulted in lower incidence of plants with symptoms and was not statistically different from the control. The pathogen R. solani was the least prevalent in the associations. The lowest accumulation of fresh and dry matter happened when the soil was infested with Fusarium solani alone. At stage 2, Jack beans in coverage provided lower incidence of root rot in muskmelon with Fusarium solani alone and in triple association (F. solani +M. phaseolina and R. solani). The use of Pearl millet had no effect on root rot incidence in most treatments. In both experiments (Jack beans andPearl millet), Macrophomina phaseolina was the fungus that prevailed in almost all associations. Jack beans and millet did not increase the fresh and dry weight of muskmelon in most treatmentsA ocorrência de doenças radiculares representa uma das principais causas de perda de rendimento na cultura do melão, com destaque para os patógenos causadores das podridões de raízes e colos, como os fungos Fusarium solani (Mart.) Sacc., Macrophomina phaseolina (Tassi) Gold. e Rhizoctonia solani Kuhn, sendo observados no meloeiro tanto de forma isolada quanto associada. A utilização de restos de cultura e material vegetal, além de melhorar as propriedades físicas do solo, favorece a atividade microbiana das espécies presentes neste ambiente e interfere negativamente sobre a população de patógenos. Portanto, objetiva-se com este trabalho avaliar as associações dos patógenos F. solani, M. phaseolina e R. solani na incidência e severidade de podridão radicular e na massa da matéria fresca e seca do meloeiro e verificar o efeito de materiais vegetais na podridão radicular causada por estes patógenos isolados ou associados. O experimento foi conduzido em duas etapas, em casa de vegetação, sendo que na primeira avaliou-se a associação de F. solani, M. phaseolina e R. solani causando podridão radicular em meloeiro, quando foi utilizado o delineamento em blocos casualizados com 8 tratamentos (F. solani; M. phaseolina; R. solani; F. solani + M. phaseolina; F. solani + R. solani; M. phaseolina + R. solani; F. solani + M. phaseolina + R. solani; solo não infestado) e 8 repetições, com unidade experimental de 1 vaso (3,5 L) com duas plantas. As características avaliadas foram: incidência de podridão radicular nas plantas de melão no fim do ciclo, severidade da doença com base em escala de notas, além da matéria fresca e seca das plantas de melão. Na segunda etapa, foi avaliado o efeito de materiais vegetais na associação desses patógenos, também em meloeiro, onde foi realizado um experimento com Feijão-de-porco (Canavalia ensiformis L. DC) e outro com Milheto (Pennisetum glaucum (L.) R. BR.). Os experimentos foram conduzidos simultaneamente, em delineamento experimental de blocos casualizados, com esquema fatorial 8 x 4, sendo 8 tipos de fungos/associação (M. phaseolina; R. solani; F. solani; M. phaseolina + R. solani; M. phaseolina + F. solani; R. solani + F. solani; M. phaseolina + R. solani + F. solani; solo sem inoculação), 4 formas de manejo (incorporado, cobertura, mulching e sem manejo) e 4 repetições. As características avaliadas foram: incidência de podridão radicular nas plantas de melão no fim do ciclo, a massa da matéria fresca e seca das plantas de melão. Os resultados de incidência de doença obtidos foram submetidos ao teste não paramétrico de Kruskal-Wallis e a massa damatéria fresca e seca foram analisados pelo teste de Scott-Knott, ambos com nível de significância a 5% de probabilidade (α = 0,05%). Na etapa 1, o tratamento no qual foram associados três patógenos F. solani, M. phaseolina e R. solani propiciou menor porcentagem de plantas com sintomas da doença e não diferiu estatisticamente da testemunha. O fitopatógeno R. solani foi o que menos prevaleceu nas associações. Quando o solo foi infestado com Fusarium solani, isoladamente, o melão obteve baixo acúmulo de matéria fresca e seca. Na etapa II, o feijão-de-porco em cobertura proporcionoiu menor incidência de podridão radicular do meloeiro quando o Fusarium solani estava sozinho e em associação tripla (F. solani +M. phaseolina e R. solani). A utilização do milheto não apresentou efeito na incidência de podridão radicular na maioria dos tratamentos. Tanto na utilização do feijão-de-porco quanto do milheto, M. phaseolina foi o fungo que prevaleceu na maioria das associações nas quais estava presente. O feijão-de-porco e o milheto não proporcionaram aumento na massa da matéria fresca e seca do meloeiro na maioria dos tratamentosConselho Nacional de Desenvolvimento Científico e Tecnológic
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
- …
