1,720,965 research outputs found
Bilans et flux de phosphore à l’échelle d’un territoire
No full textDans un contexte de dépendance européenne des ressources de phosphore minéral au niveau mondial, il semble opportun d’étudier les dynamiques territoriales locales du phosphore organique, assimilées à des « gisements locaux ». En effet, des gisements autres que minéraux existent mais ils sont soumis à des logiques de flux entre acteurs agricoles ou d’autres secteurs d’activité qui coexistent à différentes échelles : importations régionales d’amendements organiques, recyclages de sous-produits intra-région et échanges locaux entre agriculteurs et éleveurs.
Des études sur les flux de phosphore existent à l’échelle de l’exploitation ou de territoires administratifs ; elles sont en général appliquées sur une seule de ces deux échelles et de ce fait peuvent difficilement mettre en évidence les logiques des flux régionaux ou locaux entre acteurs des territoires. La présente étude s’applique à deux entités de fonctionnement agricole, que sont l’exploitation et le bassin d’approvisionnement. En particulier, le bassin d’approvisionnement semble être un concept pertinent pour étudier les logiques de ces flux puisqu’il mobilise au sein d’une filière des acteurs issus de la production, de la collecte et de la transformation agricoles.
Nous cherchons à comprendre et quantifier les flux de phosphore à l’échelle d’un territoire en mobilisant ces deux échelles afin de tester leur pertinence pour proposer des voies d’amélioration de la durabilité de la gestion territoriale du phosphore. Cette étude à caractère exploratoire vise à vérifier sa faisabilité et identifier les obstacles méthodologiques. Elle a été réalisée dans un territoire du nord du département de l’Aisne, incluant les cœurs des bassins de collecte d’une coopérative et d’une sucrerie et correspondant à deux petites régions naturelles différenciées par leurs systèmes de production : grandes cultures à dominante betteravière d’une part, polyculture et polyculture-élevage d’autre part. Dans les sols de ces deux petites régions, la classe de fertilité élevée en P (selon Regifert) est prédominante mais avec une dynamique de diminution des teneurs en P extractible dans les dix dernières années.
Dans un premier temps, les différents flux internes et externes au territoire ont été identifiés par enquête et quantifiés, soit via des bases de données gérées par la coopérative et la sucrerie soit par estimation quand les données n’étaient pas accessibles ou disponibles. La quantification de ces flux a permis d’approcher un bilan du phosphore à l’échelle du territoire. Des bilans globaux annuels du phosphore à l’échelle de l’exploitation ont été calculés après enquête sur un échantillon de 26 exploitations représentatives de la diversité des types présents sur le territoire et adhérentes de la coopérative. Sur ce même échantillon, les déterminants des choix de gestion du phosphore par les agriculteurs ont été identifiés. La quantification des flux et les bilans ont porté sur la campagne 2014-2015.
La majorité (15/26) des bilans à l’exploitation sont déficitaires, de – 53 kg/ha à -10 kg.ha-1 (figure 1). Les bilans excédentaires (+10 à +27 kg.ha-1) s’observent fréquemment dans les grandes exploitations, betteravières -fortement utilisatrices de produits organiques- ou céréalières, alors que les éleveurs ou polyculteurs-éleveurs ont des bilans équilibrés ou légèrement déficitaires. Les analyses de terre réalisées régulièrement par la majorité des agriculteurs (70%) ont beaucoup plus souvent pour but de contrôler l’absence de carence que de servir de base à un pilotage fin de la fertilisation. Les agriculteurs n’utilisant pas d’analyses de terres ont presque toujours un bilan négatif (6/7). La grande majorité des exploitations utilisent des produits organiques qui couvrent en moyenne 47 % des entrées de phosphore. Leur origine est variée : écumes de sucrerie, composts importés dans le territoire, fumiers de bovins issus d’échanges paille-fumier. La part du phosphore entrant en provenance du territoire est en moyenne de l’ordre de 20%. Certains agriculteurs ont supprimé la fertilisation minérale tout en maintenant les apports organiques mais leurs bilans sont en général négatifs
AN INDICATOR OF CROPPING SYSTEMS ECONOMIC ROBUSTNESS
No full textIn a context of increasing variability of weather conditions and prices, robustness is becoming a required characteristic of
farming and cropping systems. We propose and test an indicator of cropping systems robustness based on gross margin
variations. The method probably leads to underestimate gross margin variability because of the input data, the indicator
appeared sensitive. However, it allowed to identify the variability of the major variation factors and, above all, to evaluate
ex-ante several alternative cropping systems in a test loops design process. The method will be tested on several arable
cropping systems besides other tools to forecast yields variability
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
Design of innovative legume-based systems: the case of soybean-based cropping systems in Oise, northern France.
No full textAppropriate 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
Co-Design to Identify Lack of On-Farm Agronomic References?
No full textA large part of Northern France is targeted by measures for water protection. Within an agricultural water catchment of this area, high nitrate and pesticide concentrations have led local authorities to encourage innovative farming practices through agro-environmental measures in 2007 and 2015. For six years, a group of 23 farmers has been involved in low input farming and benefits from specific advice and sharing experience (regular meetings, field tours...). To go further, they also have asked for our support to consider new technical leverages in order to both lower pollution risks and maintain or improve farm profitability.
As the group has already improved its cropping systems (CS), we have considered i) the reasons why farmers do not use these techniques, except farm machinery availability, is that they need more references, ii) the references that they need are not obvious enough to be identified through a simple survey such as “what do you want /need to know to be able to improve your CS?” Several types of references were considered important for farmers to judge if they can introduce a technique in a given combination of CS and soil: the technique efficiency according to their objective(s), the conditions for which the technique is efficient and feasible, and its potential side effects.
Thus, to select techniques and detect references needed we have proposed to co-design new CS with each farmer based on the second step of the STEPHY approach, initially developed to co-design CS for low pesticide use. To propose all suitable techniques or leverages according to farmers’ objectives, the STEPHY tool was enlarged to other objectives such as reducing nitrates leaching or avoiding resistance development to herbicides in weeds population. To do this, data on suitable techniques were compiled according to the types of references for each potential objective.
In order to consider with each farmer the improvements he could implement, its main objectives were identified and a cropping system x soil type combination to be re-designed was chosen either for its water risk or for its economic importance. If the farmer has not or refused to introduce each proposed technique, then he had to argue the reasons.
The information collected during the interviews with farmers has been expressed as questions such as: “does sunflower introduction need to be combined with mechanical weeding to reduce herbicide use in Rapeseed/ Wheat/ Winter barley/ Pea/ Wheat rotation on a chalky soil?” Those questions have been presented to the farmers’ group as a feedback for complements and validation.
Starting from those questions, the group will have to choose techniques of interest, methods and tool (kind of experiment or survey) to test these techniques, protocols to evaluate their efficiency, their conditions of efficiency and feasibility, and their potential side effects
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
- …
