1,721,012 research outputs found
Impacts of irrigation heterogeneity on sugarcane yields, energy and water use in sub-saharan Africa.
Full text linkHess, Tim M. - Associate SupervisorSugarcane is an economically strategic crop in Sub-Saharan Africa (SSA),
underpinning the rural livelihoods and economies of many SSA countries.
Despite its economic importance, yield trends in the region have been declining
by an average of 0.03 t/ha per year over the last 60 years. However, total cane
production has been increasing by an average of one million tonnes per year over
the same period – an indication that the increase in total cane production has
largely been due to an overall expansion in cultivated area. However, this
situation is not sustainable in the long-term since land availability is limited. Whilst
irrigation has the potential to improve yields, production in SSA is typically
characterised by poor irrigation management practices as evidenced by high
levels of irrigation water use, low irrigated yields and low water productivities.
Understanding the impacts of future climate variability and drought risk on the
reliability of irrigation and identifying appropriate technology and management
options to improve yields, water and energy use and productivity are key
challenges facing the agricultural sector in SSA. Impacts of irrigation non-
uniformity on cane yields, water and energy use in SSA were identified as key
research gaps in this study.
Thus, the aim of this research was to evaluate the agronomic, environmental and
economic impacts of irrigation non-uniformity on sugarcane production in SSA.
Initially, a benchmarking study was conducted to identify opportunities to improve
cane yields and water productivity and reduce irrigation water and energy use.
Biophysical crop, water balance and economic modelling approaches were then
integrated to simulate cane yield response to water, the impacts of irrigation non-
uniformity and the relative cost and benefits of improving irrigation uniformity.
Cane yields were modelled for varying water applications and irrigation uniformity
using the DSSAT Canegro model coupled with a water balance model. The
relative financial costs and benefits of implementing different interventions to
improve irrigation management were then evaluated using a spreadsheet-based
economic model.
The results showed that there were opportunities to improve the performance of
irrigated cane production in SSA – currently characterised by lower-than-
expected yields – ranging between 83.9 and 108.9 t/ha, high irrigation water uses
and lower than potential water productivity – ranging between 5.0 and 7.8 kg/m³.
It was also established that improving irrigation uniformity leads to improved cane
yields, reduced irrigation water and energy use. It was also established that on
average a percentage improvement in irrigation uniformity could improve yields
by 0.2 – 0.5 t/ha and could reduce irrigation and energy use by 3%. These
potential yield improvements (due to improved irrigation uniformity) coupled with
a reduction in water and energy use resulted in increased revenues of between
23,300 and 70,900 MK/ha (c£18 – 65/ha) and a reduction in irrigation-related
costs by 3,700 MK/ha (c £3/ha).
Overall, the research has provided new valuable insights into the impacts of
irrigation heterogeneity on cane yields and addressed existing knowledge gaps
relating to how existing irrigation management practices in the sugarcane
industry in SSA can be improved, without the need for transformational shifts to
precision irrigation technologies. The findings provide the basis for improving
cane yields, irrigation water and energy use and productivity in both commercial
and smallholder cane production across SSA.
It is, thus, recommended that there is a need for farmers to always operate
irrigation with improved level of irrigation uniformity while ensuring proper
irrigation scheduling approaches. The implementation of irrigation uniformity
improvement interventions and adopting correct irrigation scheduling methods
would likely reduce irrigation water use, improve yield average at field level which
in turn will improve water productivity and reduce energy requirements for
irrigation. The improvement of water productivity and reduction of irrigation water
use and energy requirements would maximise crop yield benefits from irrigation
and reduce irrigation operation costs, respectively.PhD in Water, including Desig
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
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
Evaporation in fen wetlands
Full text linkWicken Fen represents a remnant of the once extensive peat fenlands of East Anglia, which survived large-scale drainage efforts intended to bring land into agricultural production due to its importance within the local economy and subsequently as a site of interest to scientists. Wicken Fen is managed so as to conserve a variety of habitats lost as a result of drainage and therefore does not represent a truly natural environment. Traditional management practices on Sedge Fen, the largest part of Wicken Fen, involve maintaining a 3 – 4 year harvesting cycle and controlling soil water levels. Previous hydrological studies of Wicken Fen have determined that soil water levels are strongly influenced by precipitation and evapotranspiration. The evaporative flux at Sedge Fen is commonly estimated by using meteorological data within empirical formulae such as the Penman Monteith equation owing to measurement difficulties. Furthermore, there has been little investigation of the evaporative loss from fens within the UK. This study aims to investigate the evaporative loss from Sedge Fen so as to better inform hydrological management and to describe evapotranspiration estimation techniques which may be employed at other fen sites. Eddy covariance measurements demonstrated that evapotranspiration from Sedge Fen was typically less than reference evapotranspiration estimates. Evapotranspiration estimates may be improved by consideration of surface parameters which can be described using meteorological data. Meteorological differences existed between Sedge Fen and the surrounding area, resulting in differing evapotranspiration estimates depending on where data was collected. Evapotranspiration measurements were used within a simple water budget model of Sedge Fen and demonstrated the lateral movement of soil water, a hydrological flux previously assumed to be of little consequence within the hydrological balance of Sedge Fen
Soil variability effects on the yield of winter wheat under variable-rate nitrogen applications
Full text linkSeven UK fields located across Oxfordshire, Southampton and W. Berkshire, five
cropped in winter wheat in 2014 and two in 2013 were investigated to assess the
effect of soil variability on mean yield and yield variance under flat-rate and variable-
rate nitrogen applications. The high level aim being to provide information to help
guide growers on how best to apply nitrogen fertiliser to increase yield and enhance
yield uniformity. Data layers were collated for shallow Electrical-Conductivity (EC),
Leaf Area Index, nitrogen application and yield. Yields were neither significantly
higher under flat-rate nor variable-rate treatment (p = 0.8356). Variation in shallow
EC was neither significantly more different in the variable-rate treatments or the flat-
rate treatments (p = 0.7862). Variability in EC held a positive relationship with yield
variability under both flat-rate (R2 = 0.2102) (p = 0.0213) and variable-rate treatment
(R2 = 0.1507) (p = 0.0176). This suggests that variable-rate treatment provided no
significant benefit in reducing yield variability
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