1,720,961 research outputs found
Influence of Soil Water Deficit and Phosphorus Application on Phosphorus Uptake and Yield of Soybean (Glycine max L.) at Dejen, North-West Ethiopia
No full textA green house experiment was conducted at Dejen, Northwest Ethiopia, with the objective of quantifying the critical soil water deficit and P levels that affect yield and yield components of soybean,
and determine the critical soil water deficit levels influencing P uptake in soybean. The treatment
consisted of factorial combination of four available soil water (ASW) deficit levels (0%, 25%, 50%
and 75%) and four levels of phosphorus (0, 10, 20, and 30 kg∙ha−1) laid out in RCBD with four replications using soy bean variety Jalale as a planting material. The experiment was conducted under green house condition at Dejen, South Ethiopia during the 2011 academic year. Air dried soil
was filled in the pots and seeds were sown on May 13, 2011. Four plants were maintained on each
pot after thinning till flowering but after flowering, the total number of plants per pot was reduced
to three as one plant which was used for measurement of root biomass. The water deficit treatments were imposed after the plants have been fully established 2 weeks after emergence just before branching stage. The water deficiency was imposed through maintaining the soil moisture
content below field capacity at the deficit levels of 25%, 50% and 75%. The 75% of ASW deficit
resulted in the longest days (45) to flowering and maturity (99) compared to the 0%, 25% and
50% deficit levels. Also, the 75% of ASW deficit level resulted in shorter plants (55 cm), the lowest
leaf area (82.6 cm2), the highest root to shoot ratio (0.0168) and the lowest DM accumulation
(161.3 gm−2) compared to the other ASW deficit levels. Likewise, the 75% of ASW deficit level gave
the lowest number of pods per plant (4.13), seeds per pod (1.69), 100 seed weight (2.54 g), seed
yield (13.4 g∙m−1), above ground biomass (174.6 g∙plant−1) and harvest index (0.08) compared to
the other ASW deficit treatments. The degree of sensitivity to drought increased dramatically
(from 0.0423 at 25% to 0.9604 at 75%) with increase in water deficit level. Tissue analysis results
indicated that the highest seed P concentration (1.285%) and uptake (432.5 g∙plant−1) were o
Nitrogen Use Efficiency of Upland Rice in the Humid Tropics of Southwest Ethiopia in Response to Split Nitrogen Application
No full text
Coffee leaf traits, bean quality and biochemistry across elevation and shade gradients in Ethiopia
No full textAccording to model projections, coffee cultivation areas should need to move to
higher elevations as suitability moves upslope to compensate for the increased
temperatures. However, shifting coffee-growing areas upslope might bring
conflicts with land use and crops other than coffee and can induce adverse socioeconomic
and environmental impacts associated with deforestation for new coffee
cultivation. Moreover, model projections are largely limited to ex situ experiments
based on downscaled global climate models, and thus empirical data are still
needed to assess climate change impacts on coffee production in the future in
Ethiopia. Furthermore, conditions such as shade tree canopy closure, soil fertility
and elevation may either ameliorate or exacerbate climate change impacts. In the
absence of significant interventions, this could result in a considerable land use
change, increased vulnerability of coffee-dependent livelihoods, and a potential
shortage of coffee supply. Hence, to generate trustworthy and accurate
information for climate-resilient Ethiopian coffee production, more field-based
experiments are needed.
In this PhD thesis, we used coffee plants growing at contrasting elevations using a
space-for-time substitution approach for warming in southwest Ethiopia. The
coffee plants are superimposed under various shade tree species with multi-strata
canopy architecture. In so doing, the potential of increasing canopy closure in
modulating responses to increasing temperature and the associated effect on
coffee plant traits, green bean quality and biochemistry were thoroughly explored.
Based on our findings, we were able to identify potential limiting factors to close
the coffee quality gap by providing improved management recommendations
tailored to the local ecological conditions while acknowledging the dynamic
drivers (mainly resource availability and climatic variability) for the long-term
sustainability of the coffee industry
Yield Related Traits and Yield of Maize (Zea Mays L.) as affected by Green Manuring and Nitrogen Levels at Mizan Teferi, South-west Ethiopia.
No full textSoil fertility decline is a major constraint to agricultural production and productivity in the
areas of Bench Maji Zone due to high rates of soil erosion, leaching of nutrients as a result
of high rainfall, continuous removal of crop residues from crop fields, use of cow dung for
other purposes and low inherent soil fertility. A field experiment was conducted during the
main rainy season of 2009 at the Mizan ATVET College to study the effects of green manure
(GM) and nitrogen (N) levels on yield related traits and yield of maize. Factorial combinations
of three rates of GM (0, 5 and 10 tons/ha) and four levels of N (0, 20, 40 and 60 kg/ha) were
laid out in randomized complete block design with three replications. Before incorporation
of the GM, a composite soil sample was taken from the experimental plots (0-30 cm depth) to
observe some selected soil physico-chemical properties. At harvest, the crop was
partitioned into stover and grain for the determination of N content and N uptake, fertilizer
recovery and use efficiencies were calculated. Results of the soil analysis showed that the
soil of the experimental site was sandy clay loam in texture; strongly acidic in reaction (pH
=4.7); very high in OM content (6.51%); low to medium in total N (0.2%); very low in available
P (2 mg/kg) and medium in CEC (20 cmolc/kg). Significant effects (P <0.05) were observed
on days to silking, plant height, number of grains per ear, grain yield, stover yield, 1000
kernels weight, harvest index and number of barren plants per plot and the effect of GM was
also significant (P <0.05) on plant height, number of grains per ear, grain yield, stover yield
and 1000 kernels weight. On the other hand, the interaction effect of N and GM was
significant (P <0.05) only on plant height, number of grains per ear, grain yield and stover
yield. The maximum grain yield (4625 kg/ha) was obtained from the application of the
highest N and GM rate (60 kg N/ha and 10 tons GM/ha) whereas the maximum plant height
(199.7 cm) was attained at 60 kg N/ha and 0 ton GM/ha. On the other hand, the highest
values of thousand kernels weight (294.1 g) and harvest index (59.7%) were obtained from
the application of the highest N rate. Increasing N affected grain and stover N contents and
total N uptake showing increasing trend with increasing N rate in most of the grain, and
decreasing trend with increasing N rate in stover. The physiological use efficiency (PUE) of
N exhibited non-consistent trend to the increased application of N and GM; however, at
higher rates of N and GM, it was reduced. On the other hand, the apparent N recovery (ANR)
and agronomic use efficiency (AUE) responded more or less positively to the increased
application levels of N and GM. Higher application rates of GM increased the ANR and AUE
of N nutrient. Generally, the inorganic nutrient source applied in sole and in combination
with organic have improved most of the yield related traits and yield of maize while the
organic nutrient source applied in sole have improved only some of the them. However, this
one season study has to be conducted through a number of seasons and locations of
similar agro-ecology, soil type and crop in order to draw concrete conclusions and make
recommendations
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
Growth and Yield of Rice (Oryza sativa L.) as Affected by Time and Ratio of Nitrogen Application at Jimma, South-West Ethiopia
No full text– Insufficient nitrogen supply in inappropriate
timing is an important constraint to productivity of upland
rice (Oryza sativa L.), and there is limited information
available on optimal timing of N application for upland rice
in Ethiopia including Jimma area. Field experiment was
conducted on three upland rice varieties (Gumara, Ediget
and Nerica-4) in a completely randomized block design with
3 replications to determine the effects of timing and ratio of
nitrogen application on growth and yield during the 2014
cropping season on acidic nitisol (soils possessing nitic
property) at the Jimma University, College of Agriculture
and Veterinary Medicine research site. The N-timing
treatments were: N1
(50% at sowing and 50% at active
tillering stage), N2
(25% at sowing + 50% at active tillering
stage and 25% at panicle initiation), N3
(25% at sowing +
25% at active tillering stage and 50% at panicle initiation),
and N4
(33% at sowing + 33% at active tillering stage and
33% at panicle initiation). The highest grain yields (1070
kg/ha), biomass yields (3333 kg/ha), total number of grains
per panicle, and harvest index were recorded from ‘Ediget’
variety at the N2 combination (25% at sowing + 50% at
active tillering stage and the remaining 25% at panicle
initiation), followed by N3 and N4 combinations. The lowest
grain yields (117 kg/ha) and biomass yields (767 kg/ha) were
recorded from Nerica-4 variety at the N2 combination.
Nerica-4 variety produced minimum grain and biomass
yields across all the N combinations. Most of the parameters
exhibited maximum performance under N2 and N3
combinations across all the varieties. The varietal treatments
had highly significant (P<0.001) effects on the total number
of panicles, grain yield, biomass yield and harvest index.
Grain yield was positively correlated (P<0.01) with plant
heights (r=0.68**), number of filled grains per panicle
(r=0.52**) and thousand grains weight (r=0.61**) and
negatively correlated with most of the traits. Number of
panicles was the most important component of yield,
accounting for about 87% of the variation in rice yield. Thus,
rice cultivation and its nitrogen fertilizer management in the
area is concerned, the variety ‘Ediget’ was recommended for
higher grain and biomass yields regardless of the N-timing
treatments. Concerning the N-timing treatments, the f
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
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