1,721,035 research outputs found
Nitrogen Management for Corn Following Alfalfa: Field, Literature, and Geographic Analyses
Full text linkUniversity of Minnesota Ph.D. dissertation. December 2013. Major: Applied Plant Sciences. Advisors: Jeffrey A. Coulter, Michael P. Russelle. 1 PDF (xvi, 185 pages) + 4 supplementary files (2 Word documents & 2 Excel tables).First- and second-year corn (Zea mays L.) following alfalfa (Medicago sativa L.) often require less supplemental N than corn grown continuously or following soybean [Glycine max (L.) Merr.]. The results of seven on-farm trials indicated that alfalfa can provide the entire N requirement of first-year corn no-till planted following alfalfa terminated in the fall. Eight other on-farm trials also indicated that first-year corn following alfalfa often does not require supplemental N (fertilizer or manure). The conclusion that first-year corn following alfalfa often requires no fertilizer N has been supported for decades, yet no research has identified site-specific conditions that cause first-year corn to respond to supplemental fertilizer N. The most widely used predictive test, the presidedress soil nitrate test (PSNT), had limited success in identifying response to N when trials from this study were combined with literature research; the test was 55% accurate across 94 site-years. An end-of-season test used to assess N supply to corn, the corn stalk nitrate test (CSNT), also was not successful in 11 trials at identifying when first-year corn would have required fertilizer N. An analysis of the literature was conducted to identify site-specific conditions that cause first-year corn following alfalfa to respond to N. Soil texture and alfalfa termination timing on medium-textured soils were significant covariates for identifying responsiveness to fertilizer N in first-year corn. First-year corn following alfalfa rarely required fertilizer N when alfalfa harvested for ¡Ý2 yr was fall-terminated on medium-textured soils; corn following alfalfa harvested 1 yr responded more frequently. The frequency of response to fertilizer N increased greatly when alfalfa was grown on coarse- or fine-textured soils and when alfalfa was terminated in the spring on medium-textured soils. For these conditions, combinations of alfalfa stand age and weather conditions explained much of the variation in whether a site would respond to N and the economically optimum N rate (EONR) at various price ratios (PRs) of fertilizer N/corn grain. The regression models developed to predict fertilizer N response appear robust, but require independent validation. Alfalfa also provides N to the second consecutive corn crop following alfalfa termination. Results from 28 on-farm trials in Minnesota and Iowa revealed that second-year corn required fertilizer N only 50% of the time. The same trend occurred when these trials were combined with 39 trials in the literature. The PSNT had higher accuracy for second-year corn (65%) than for first-year corn, but improvements in accuracy are still necessary in order for this test to be a reliable tool for growers. A geographic analysis revealed that growers in the U.S. Corn Belt region of the upper midwestern United States (North Dakota, South Dakota, Nebraska, Minnesota, Iowa, and Wisconsin) rotate alfalfa more frequently than in other parts of this region and that alfalfa phase length, soil texture, and year affect the type of crops grown for 2 yr following alfalfa termination. Supplemental files include data and references used for the literature analysis (Supplemental Table S4.1; Supplement S4.2), data used for analysis of second-year corn response to N (Supplemental Table S5.1), and alfalfa hectare estimates by state and year for the geographic analysis (Supplemental Table S6.1).Yost, Matt Alan. (2013). Nitrogen Management for Corn Following Alfalfa: Field, Literature, and Geographic Analyses. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/162555
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Yield Potential and Nitrogen Requirements of Miscanthus × giganteus on Eroded Soil
Full text linkMiscanthus × giganteus yield and fertilizer N requirements have been well studied in Europe and parts of the United States, but few reports have investigated its production on eroded claypan soils economically marginal for grain crops. This study was conducted to evaluate yield potential and fertilizer N strategies for young and mature M. × giganteus on eroded soils. Constant (medium, high) and priming (low, medium, high) fertilizer N rates were applied during 2013 to 2015 at three locations in Missouri to young stands planted in 2012. Constant rates (low, medium, high) also were applied to one mature stand planted in 2007. Winter biomass yield (13.3–23.8 Mg ha–1) was comparable to more productive soils and increased with N fertilization at only two sites with young stands. At one location, yield increased by 44, 48, and 82% with fertilization in 2013, 2014, and 2015, respectively, while the other location increased by 43% only in 2015. At both locations, the medium constant rate (67 kg N ha–1 yr–1) was the lowest rate that maximized total yield across 3 yr. This rate was efficient as it did not increase N removal in harvested biomass. Fertilization always increased leaf chlorophyll concentration (LCC) and site-years with relative LCCM. × giganteus on eroded soils with low organic matter content, and relative LCC can accurately identify when fertilization is required.This article is published as Yost, Matt A., Bryan K. Randall, Newell R. Kitchen, Emily A. Heaton, and Robert L. Myers. "Yield Potential and Nitrogen Requirements of× on Eroded Soil." Agronomy Journal 109, no. 2 (2017): 684-695. 10.2134/agronj2016.10.0582. Posted with permission.</p
Variations on the Author
Full text link“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
Full text linkWe 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
Full text linkWe 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
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