1,720,960 research outputs found
A numerical simulation method to calculate the solar radiation inside photovoltaic greenhouses
No full textCarbon footprints and social carbon cost assessments in a perennial energy crop system: A comparison of fertilizer management practices in a Mediterranean area
Full text linkAgriculture is strongly linked to climate change and has a two-sided relationship with climate change. Although climate change contributes to reducing agricultural productivity, the primary sector is responsible for the production of greenhouse gas (GHG) emissions; on the other hand, the primary sector could mitigate emissions to foster soil carbon sequestration. Specifically, perennial energy crop systems could produce relevant environmental and socio-economic benefits. This study aimed to highlight the potential efficacy of various fertilizer management strategies in reducing GHG emissions and increasing the social value obtained from carbon storage. Using two methodological approaches, namely, the carbon footprint (CF) and social carbon cost (SCC) methods, five nitrogen fertilization patterns (low input, LI; high input, HI; LI + biochar, LI + Bi; LI + cover crop, LI + CC; and LI + Bi + CC) were compared in an experiment on cardoon cultivation for three consecutive growing seasons. GHG release exceeded GHG removal and ranged from 0.20 (HI) to 0.14 (LI + CC) t CO2e per production unit. LI + CC reduced GHG emissions and optimized yield. The rates of carbon sequestration ranged from 72.7 (HI) to 26.2 (LI) t CO2e t −1 of biomass. Furthermore, the combined use of biochar and a cover crop had no positive effects on C sequestration or GHG emission reduction, unlike these treatments individually. In fact, LI + Bi provided the highest value for C storage (61.1 t CO2e t − 1 of biomass), and LI + CC had the best GHG balance (0.14 t CO2e per production unit). The monetary evaluation of C storage showed that HI would produce the greatest benefits until 2050 (i.e., 9 K US dollars per t CO2e). Although a single best option was not identified among the fertilizer management practices, identifying the optimal trade-offs among productivity, GHG emissions reduction and SCC value is important in ensuring that an energy crop will provide food security as well as environmental and socio-economic sustainability. Furthermore, a potential optimal solution could allow improvements in long-term crop system planning and land use and the development of effective strategies to combat climate change
C-sequestration and resilience to climate change of globe artichoke cropping systems depend on crop residues management
Full text linkGlobe artichoke is one of the most intensively cultivated horticultural species in Mediterranean regions. In this context, sustainable agronomic management is a requisite to increase the soil carbon content, making the artichoke cultivation system more resilient to climate change. A 10-year experiment was considered to forecast the influence on soil C dynamic of three globe artichoke managements: monoculture with dry crop residues incorporation (conventional monoculture), monoculture with the inclusion of a cover crop (alternative monoculture), and rotation with cauliflower plus cover crop (biannual rotation). During the 2006–2016 period, total soil organic carbon content and plant C inputs to soil were measured. RothC model was used to predict the effect on the soil C stock and C sequestration potential in 20 years of the three managements tested in the field, plus a hypothetical conventional scenario with no residues’ incorporation (no residues). Plant C inputs increased according to the number of crops in rotation in each system, resulting 25% lower in conventional monoculture with respect to biannual rotation, whereas the C stock change was significantly higher (p < 0.01) in conventional and alternative monoculture (+ 7.57 and 7.14 t C ha-1) compared to biannual rotation (-1.03 t C ha-1). In the 20-year predictions, all the systems had a positive C balance. The soil organic carbon change (t C ha-1) for the future climate was + 7.2 for alternative monoculture and + 0.6 for monoculture with residues removals. For the first time, in this study, we clearly shown in the long term and in a climate change perspective that an improper crop residues management might lead to a loss of soil fertility in intensively cultivated horticultural soils under Mediterranean climate. The adoption of biannual rotation with cauliflower needs to be evaluated carefully because it proved to be less efficient in terms of C sequestration potential
Agricultural sustainability estimation of the European photovoltaic greenhouses
Full text linkThe integration of the photovoltaic (PV) energy in the greenhouse farm has raised concerns on the agricultural sustainability of this specific agrosystem in terms of crop planning and management, due to the shading cast by the PV panels on the canopy. The PV greenhouse (PVG) can be classified on the basis of the PV cover ratio (PVR), that is the ratio of the projected area of PV panels to the ground and the total greenhouse area. In this paper, we estimated the yield of 14 greenhouse horticultural and floricultural crops inside four commercial PVG types spread in southern Europe, with PVR ranging from 25 to 100%. The aim of the work is to identify the PVG types suitable for the cultivation of the considered species, based on the best trade-off between PV shading and crop production. The daily light integral (DLI) was used to compare the light scenarios inside the PVGs to the crop light requirements, and estimate the potential yield. The structures with a PVR of 25% were compatible with the cultivation of all considered species, including the high light demanding ones (tomato, cucumber, sweet pepper), with an estimated negligible or limited yield reduction (below 25%). The medium light species (such as asparagus) with an optimal DLI lower than 17 mol m−2 d−1 and low light crops can be cultivated inside PVGs with a PVR up to 60%. Only low light demanding floricultural species with an optimal DLI lower than 10 mol m−2 d−1, such as poinsettia, kalanchoe and dracaena, were compatible inside PVGs with a PVR up to 100%. Innovative cropping systems should be considered to overcome the penalizing light scenarios of the PVGs with high PVR, also implementing LED supplementary lighting. This paper contributes to identify the sustainable PVG types for the chosen species and the alternative crop managements in terms of transplantation period and precision agriculture techniques, aimed at increasing the crop productivity and adaptability inside the PVG agrosystems
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
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