1,720,962 research outputs found
Microbial-based soil quality indicators in irrigated and rainfed soil portions of Mediterranean olive and peach orchards under sustainable management
No full textThe main objective of this study was to apply microbial indicators of soil quality in drip-irrigated olive and peach orchards managed with sustainable agricultural practices. Soil characterization was carried out in different areas of the orchards along the row, under the drippers (Rdr), and along the inter-row, rainfed (IRrf), to evaluate the effects of irrigation. Two parameters were followed during one year: a) a biochemical soil indicator (Nc/Nk ratio) based on soil N/C turnover and soil enzyme activities, and b) the abundance of three important N-cycling genes (nifH, amoA and nosZ). Localized irrigation caused higher values of water content in the Rdrareas, compared to IRrf. The Nc/Nk ratio exhibited all the attributes of a reliable soil fertility indicator, being generally higher in irrigated Rdr areas. The abundance of nifH and amoA in the soil showed a trend similar to Nc/Nk, being affected by higher soil water content, while nosZabundance was generally insensitive to irrigation. Both Nc/Nkand gene abundances, much more than the measured chemical, biochemical and molecular soil parameters considered alone, can give a precise idea on N and C soil dynamics, that in turn, affect soil quality and fertility
Impact of long term soil management practices on the fertility and weed flora of an almond orchard
Full text linkoil management techniques can definitely influence soil quality, and particularly soil organic matter content, biological complexity, structure, and water holding capacity. Tillage may also have a negative effect by increasing erosion and organic matter oxidation processes, which have unavoidable repercussions on fertility. The objective of the current research was to test the effects of five different management techniques applied for 35 years on a rain-fed almond grove (Prunus amygdalus Batsch) in a hot-dry environment on some physicochemical, hydrological, and biological parameters. The following soil management techniques were compared: no-till (NT), with weed control by preemergence herbicides; NT, with chemical weed control by foliar herbicides; NT, with weed control by mowing; tillage, with sowing and field bean green manuring; and conventional tillage. The current survey supplied interesting results, considering the typical soil and climate conditions of the tested area (southern Italy), characterized by high summer temperatures, low rainfall, clay loam soil, and an arable layer of 0.40 m. The most influenced values are those concerning the organic matter due to the supply of biomass resulting from weed mowing or field bean green manuring. The NT system with a single mowing in the spring seems to induce a higher water holding capacity (–15,000 hPa) as compared with the traditionally plowed soil. The biomass incorporation through field bean green manure resulted in a higher available water content (11.82%). All practices favoring an increase in organic matter induced a subsequent increase of microbial biomass content. The number of existing families and species of weed flora was largely influenced by different soil management techniques, as shown by the greater adaptation of grasses to the management practices involving weed control by foliar herbicide or mowing, and of several species associated with the technique involving the application of preemergence herbicides. In general, the almond orchard management involving minimum soil disturbance and the supply of biomass resulting from specially sown cover crops or weed development have shown substantial benefits to the physicochemical, hydrologic, and biologic soil properties.Soil management techniques can definitely influence soil quality, and particularly soil organic matter content, biological complexity, structure, and water holding capacity. Tillage may also have a negative effect by increasing erosion and organic matter oxidation processes, which have unavoidable repercussions on fertility. The objective of the current research was to test the effects of five different management techniques applied for 35 years on a rain-fed almond grove (Prunus amygdalus Batsch) in a hot-dry environment on some physicochemical, hydrological, and biological parameters. The following soil management techniques were compared: no-till (NT), with weed control by preemergence herbicides; NT, with chemical weed control by foliar herbicides; NT, with weed control by mowing; tillage, with sowing and field bean green manuring; and conventional tillage. The current survey supplied interesting results, considering the typical soil and climate conditions of the tested area (southern Italy), characterized by high summer temperatures, low rainfall, clay loam soil, and an arable layer of 0.40 m. The most influenced values are those concerning the organic matter due to the supply of biomass resulting from weed mowing or field bean green manuring. The NT system with a single mowing in the spring seems to induce a higher water holding capacity (–15,000 hPa) as compared with the traditionally plowed soil. The biomass incorporation through field bean green manure resulted in a higher available water content (11.82%). All practices favoring an increase in organic matter induced a subsequent increase of microbial biomass content. The number of existing families and species of weed flora was largely influenced by different soil management techniques, as shown by the greater adaptation of grasses to the management practices involving weed control by foliar herbicide or mowing, and of several species associated with the technique involving the application of preemergence herbicides. In general, the almond orchard management involving minimum soil disturbance and the supply of biomass resulting from specially sown cover crops or weed development have shown substantial benefits to the physicochemical, hydrologic, and biologic soil properties
Nitrogen dynamics and N-cycling bacterial communities in a Mediterranean olive orchard under a sustainable farming system
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Effetti dell’agricoltura sostenibile sulla qualità del suolo di colture di oliveto e pescheto
No full textNel corso degli ultimi decenni, pratiche agricole intensive come la lavorazione del suolo, un elevato impiego di concimi minerali, l’applicazione di acqua irrigua di bassa qualità e la rimozione dei residui di potatura, hanno determinato la perdita di fertilità e l'esaurimento di carbonio organico nel suolo (SOC). Al contrario, le pratiche di gestione sostenibile possono contribuire a recuperare la produttività e la biodiversità del suolo. L'obiettivo principale di questo studio è stato quello di analizzare alcuni parametri di fertilità del suolo in un oliveto ed un pescheto gestiti in modo sostenibile. In particolare, nell’oliveto sono state adottate le seguenti pratiche agricole: irrigazione a goccia con acque reflue urbane trattate, assenza di lavorazione del suolo, inerbimento naturale, pacciamatura con residui di potatura. Il pescheto è stato gestito secondo il Reg. 834/07 sull’agricoltura biologica e ha previsto l’impiego di compost e di irrigazione a goccia. Nel corso di un anno, sono stati effettuati tre campionamenti di suolo (marzo, giugno, ottobre) e in ciascun frutteto, sono state individuate due aree di campionamento: fila (sotto gli emettitori) e inter-fila (solo apporti idrici pluviale).
Il grado di qualità del suolo è stato espresso dal rapporto Nc/Nk, dove Nk è il valore di azoto Kjeldahl del suolo, mentre Nc è una funzione lineare della biomassa microbica carbonio, della capacità di mineralizzazione dell’N e di tre attività enzimatiche del suolo (fosfomonoesterasi, β-glucosidasi e ureasi) coinvolte nel turnover di N e influenzate dalla sua disponibilità.
I risultati hanno evidenziato un effetto positivo delle pratiche di agricoltura sostenibile e dell’irrigazione in tutti i prelievi del pescheto e nei primi dell’oliveto, attestati dai valori dell’indice Nc/Nk maggiori per la tesi sperimentale rispetto al controllo. Da questi valori, sono stati calcolati gli indici Nc/Nk, riportati in tabella 2, maggiori nella tesi irrigata rispetto al controllo inter-fila nei prelievi di marzo e giugno (valori quasi raddoppiati nel prelievo di marzo), mentre nel prelievo di ottobre l’indice Nc/Nk è risultato essere maggiore nel controllo. Sono stati inoltre determinati parametri fisico-chimici del suolo. È in corso l’indagine molecolare della popolazione microbica di questi suoli mediante l’amplificazione in Real Time PCR dei geni codificanti subunità della nitrogenasi (nifH), dell’ammoniaca monossigenasi (amoA), nitrito reduttasi (nirK e nirS), e nitroso ossido riduttasi (nosZ), volta a quantificare la frazione della comunità microbica coinvolta nei processi chiave del ciclo dell'azoto nel suolo. L'aumento delle conoscenze sui processi legati ai microrganismi del suolo coinvolti nelle dinamiche che influenzano la disponibilità di C e di N per le piante, può condurre all’ottimizzazione delle strategie di gestione sostenibili del suolo. Tale approccio si sposa con un moderno e multifunzionale dell'agricoltura, basato sulla qualità dei prodotti, la tutela dell'ambiente, il risparmio di risorse naturali (suolo e acqua in primis) e la promozione della salute umana
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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