1,720,963 research outputs found
Prairie strips’ effect on transport of antimicrobial resistance indicators in poultry litter
Get PDFPoultry litter is a valuable nutrient resource for agricultural production but is also a potential source for introducing antibiotic resistance genes (ARGs) and litter-associated bacteria (LAB) to the environment. Prairie strips have been demonstrated as an effective conservation practice to improve environmental quality in agroecosystems. This research aims to assess prairie strips’ potential for reducing the transport of LAB and ARGs in runoff after litter application. Plot-scale rainfall simulations were performed using a replicated block design, with soil and surface runoff samples taken during the rainfall event. Microbial taxa and ARGs were characterized in the litter, soil, and water samples. In plots with litter application, LAB and ARGs were mainly detected in runoff, with very low detection in soils. Detection of ARGs in runoff, irrespective of strip installations, is consistent with previous observations of litter as a source of antimicrobial resistance (AMR) risks. The effectiveness of prairie strips to remove LAB and ARGs varied. In two of the three prairie strip plots, fewer AMR indicators were detected relative to control plots, suggesting that the prairie strips can potentially reduce these risks. In one plot, which was also associated with increased flow rate, we observed increased AMR indicators despite the installation of a prairie strip. Our observations highlight the need to prioritize understanding of soil properties even within the same site. Although we show that prairie strips can potentially reduce AMR risks, further research is needed to better understand the influence of rainfall timing, soil, and litter characteristics.This is the published version of the following article: Flater, Jared S., Laura M. Alt, Michelle Soupir, Thomas B. Moorman, and Adina Howe. Prairie Strips Impact on Transport of Antimicrobial Resistance Indicators in Poultry Litter. 2022. DOI: 10.1002/jeq2.20333.
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Understanding soil bacterial communities for sustainable agriculture
Get PDFNutrient loss from synthetic fertilizer use contributes to poor water quality, conversion of native landscapes to agricultural production reduces biodiversity, and antibiotic use in animal production contributes to antibiotic resistance. Therefore, agriculture can have adverse effects on local and global environments. Soil bacteria mediate processes that can influence the impact of agriculture on the environment. Characterizing soil bacterial communities in response to changes in agricultural management may inform scientific understanding of how management decisions can alter soil bacteria. Several management practices aim to reduce the impact of agriculture on the environment and improve its sustainability. Offsetting synthetic fertilizer use with organic amendments can reduce nitrate losses and improve water quality. However, the microbially mediated and hard to predict the release of plant-available nutrients from organic amendments can limit their adoption and use. Installation of prairie strips as a conservation practice can reduce sediment loss and provide habitat for native animals, improving diversity. However, the impact of prairie strips on the soil bacterial community remains under characterized. Grasses can filter antibiotics and antibiotic resistance genes in runoff water from manure treated fields, though the ability of prairie strips to reduce antibiotic resistance in runoff water is not understood. The experiments described in this dissertation contribute to a scientific understanding of soil bacteria's response to organic amendment and prairie strip installation, as well as the impact of prairie strips on attenuating the transport of manure associated bacteria and antibiotic resistance genes. Soil bacterial communities' response to organic amendments of varying quality was compared against soil receiving no amendment during an incubated microcosm study. Soil bacterial communities exhibited community similarity in two temporal groupings in all amended and un-amended soils. In response to organic several bacterial taxa became significantly more abundant in amended soils and were associated with amendment quality. Alpha and beta diversity of soil bacteria were compared between agricultural soil and prairie strip soil at two sites. Prairie strips examined were less than five years old and did not significantly differ from agricultural soils at the two sites. Bacterial richness, Shannon's diversity, and Simpson's diversity were significantly greater in prairie soils than agricultural soils at one site and only in response to rainfall. The abundance of manure-associated bacteria in runoff water was compared between plots receiving manure without prairie strips and plots receiving manure. Prairie strip appended plots had lower abundances of manure associated taxa and lower detection of antibiotic resistance genes than plots without prairie strips. Conservation practices designed to reduce nutrient loss, such as the use of composts or the installation of prairie strips, are essential practices that can improve agricultural sustainability, yet have impacts on bacterial dynamics that are not well understood. Characterizing bacterial communities in soils under various conservation practices will inform our understanding of how these practices impact the soil bacterial community.</p
Effects of organic fertilization on soil bacterial community structure in incubated microcosms
Get PDFAddressing the growing demand for food from a burgeoning population requires agricultural methods that sustainably support increases in crop production while maintaining environmental health. Agricultural practices that include the use of compost, in lieu of mineral fertilizers, have been shown to reduce environmental impacts and improve soil health. Producers seeking to improve sustainability through compost use are challenged by the chemical form and availability of nutrients in organic amendments, limiting their ability to predict when nutrients will be available to crops. To better understand nutrient dynamics in soils amended with organic fertilizers, we compared the soil microbial community response to amendments with differing carbon and nitrogen content. Composted horse manure was chosen to represent an organic high carbon amendment, and alfalfa hay was chosen to represent a high nitrogen amendment. Amended soils were incubated for 97 days and destructively sampled on seven progressively longer incubation intervals. DNA was extracted for microbial community characterization, and measurements of nitrogen, carbon, and biomass were also compared for all samples. Our results showed significant shifts in soil microbial communities due to both time and amendment. Nutrient release was highly associated with amendment composition, with alfalfa showing the greatest release of plant available nutrients. We observed complex interactions between soils and amendments, with specific bacteria associated with nitrogen and carbon metabolism. These bacteria are targets for further characterization and better knowledge of their role in decomposition may contribute to the increased use of high organic matter fertilizer by producers and lead to a better understanding of sustainable crop production techniques.</p
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
Understanding soil bacterial communities for sustainable agriculture
Get PDFNutrient loss from synthetic fertilizer use contributes to poor water quality, conversion of native landscapes to agricultural production reduces biodiversity, and antibiotic use in animal production contributes to antibiotic resistance. Therefore, agriculture can have adverse effects on local and global environments. Soil bacteria mediate processes that can influence the impact of agriculture on the environment. Characterizing soil bacterial communities in response to changes in agricultural management may inform scientific understanding of how management decisions can alter soil bacteria.
Several management practices aim to reduce the impact of agriculture on the environment and improve its sustainability. Offsetting synthetic fertilizer use with organic amendments can reduce nitrate losses and improve water quality. However, the microbially mediated and hard to predict the release of plant-available nutrients from organic amendments can limit their adoption and use. Installation of prairie strips as a conservation practice can reduce sediment loss and provide habitat for native animals, improving diversity. However, the impact of prairie strips on the soil bacterial community remains under characterized. Grasses can filter antibiotics and antibiotic resistance genes in runoff water from manure treated fields, though the ability of prairie strips to reduce antibiotic resistance in runoff water is not understood.
The experiments described in this dissertation contribute to a scientific understanding of soil bacteria's response to organic amendment and prairie strip installation, as well as the impact of prairie strips on attenuating the transport of manure associated bacteria and antibiotic resistance genes. Soil bacterial communities' response to organic amendments of varying quality was compared against soil receiving no amendment during an incubated microcosm study. Soil bacterial communities exhibited community similarity in two temporal groupings in all amended and un-amended soils. In response to organic several bacterial taxa became significantly more abundant in amended soils and were associated with amendment quality. Alpha and beta diversity of soil bacteria were compared between agricultural soil and prairie strip soil at two sites. Prairie strips examined were less than five years old and did not significantly differ from agricultural soils at the two sites. Bacterial richness, Shannon's diversity, and Simpson's diversity were significantly greater in prairie soils than agricultural soils at one site and only in response to rainfall. The abundance of manure-associated bacteria in runoff water was compared between plots receiving manure without prairie strips and plots receiving manure. Prairie strip appended plots had lower abundances of manure associated taxa and lower detection of antibiotic resistance genes than plots without prairie strips.
Conservation practices designed to reduce nutrient loss, such as the use of composts or the installation of prairie strips, are essential practices that can improve agricultural sustainability, yet have impacts on bacterial dynamics that are not well understood. Characterizing bacterial communities in soils under various conservation practices will inform our understanding of how these practices impact the soil bacterial community
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