1,721,012 research outputs found
Assessing specific vulnerability of shallow aquifers to pesticide using GIS tools. data needs and reliability of index-overlay methods: An application to the san giuliano terme agricultural area (Pisa, Italy)
Full text linkPesticides play a crucial role in regulating crop production by reducing crop losses and increasing crop yield and quality. However, they may threaten surface and groundwater, a phenomenon occurring at global scale, potentially causing environmental damage and prohibition of water use or high treatment costs for drinking water. Assessing spatially-defined aquifer vulnerability to pesticide is then important, as it may allow defining agricultural areas where pesticides should be used following well-defined agronomic practices/limitations. In this study, after a brief review of recent studies on aquifer vulnerability assessment to pesticide, we applied the Vulnerability Index method to the agricultural area of the Municipality of San Giuliano Terme (Pisa, Italy) in order to focus on the data needs and discuss the reliability of this method (as an example of index-overlay methods). The proposed method needs a relatively small number of parameters compared to other more complex ones. Despite a such a small number of parameters, some were not easily available in our case study. Thus, some assumptions were made. This led to vulnerability maps with reduced reliability, no validation with groundwater samples, and little practical use. This means that to produce robust but static vulnerability assessments, large datasets are needed. In turn, the cost of data gathering may be high. The value of these data may, however, be increased, and the cost better justified if the analyses are based on process-based or advanced statistical methods. While the future for vulnerability assessment methods is the use of process-based/advanced statistical methods, index-overlay methods, as a preliminary step for process-based simulation analysis, may still provide initial and relatively quick insights on potential leaching of pesticides. This in turn may support extension services in delivering timely and relevant advices on the use of such pesticides to farmers and owners of plant nurseries and greenhouses
La mineralizzazione della sostanza organica
No full textPer provare a quantificare la sorgente di nutrienti costituita in seguito alla mineralizzazione
della sostanza organica dei terreni, pur in mancanza di dati sperimentali, si sono
tentate due metodologie di stima diverse. Il primo metodo è comunemente utilizzato in
agronomia e prevede l’uso del coefficiente di mineralizzazione della sostanza organica,
che in ambiente mediterraneo è da considerare relativamente costante e compreso fra
l’1.5 e il 2.0%. Il secondo metodo parte dall’ipotesi, sperimentalmente confermata in
contesti caratterizzati da suoli torbosi, che la mineralizzazione della sostanza organica
sia correlabile con la subsidenza e quindi quantificabile attraverso una valutazione di
quest’ultimo processo.
Nel nostro caso studio è stato possibile addirittura verificare l’esistenza di una correlazione
spaziale fra i due fenomeni attraverso l’interpolazione spaziale dei dati relativi al
contenuto in sostanza organica dei terreni (ricavata dal già citato data-base georiferito
dei suoli del comprensorio, si veda il Cap. 2.5) e di un immagine raster costruita sulle
differenze di quota registrate nel 1935 e nel 2006, fornitaci dall’Autorità di Bacino del
fiume Serchio. Il calcolo della correlazione è stato effettuato facendo riferimento alla sola
superficie comune ai due strati informativi, corrispondente a circa 1640 ha
Applicazione per la stima dell'evapotraspirazione effettiva delle colture
No full textL’applicazione realizzata si propone la stima dei consumi idrici delle colture attraverso
l’integrazioni di più moduli finalizzati alla quantificazione dei diversi termini del bilancio:
contenuto idrico del suolo nello strato esplorato dalle radici, evapotraspirazione potenziale
e massima della coltura (ETP ed ETM), calcolo delle somme termiche della coltura
considerata, accrescimento radicale, acqua disponibile, evapotraspirazione effettiva
(ETE), ricorso all’irrigazione, contributo della falda.
Il modello non simula la crescita reale della coltura, né considera eventuali fattori di
stress che possano deprimere i processi fisiologici della pianta. L’evapotraspirazione effettiva
così stimata rappresenta i consumi di una coltura coltivata secondo adeguate pratiche
agricole, in buone condizioni fitosanitarie e che risenta degli eventuali stress idrici
solo in termini quantitativi (rifornimento di acqua) e non in termini qualitativi (perdita
di funzionalità).
Gli input necessari al funzionamento dell’applicazione sono i dati giornalieri di tipo meteorologico
e i parametri relativi alla fisiologia della coltura, alle caratteristiche del suolo
e al management agronomico.
A questo riguardo si è quindi provveduto ad un’analisi delle serie dei dati climatici disponibili,
provenienti dalla rete di monitoraggio agrometeorologico dell’ARSIA e del Servizio
Idrologico Regionale.
In particolare, per quanto riguarda temperatura, radiazione globale, umidità relativa, velocità
del vento (variabili necessarie al calcolo dell’ETP), sono stati analizzati i dati delle
stazioni di Metato e Lido di Camaiore (dell’ARSIA), le uniche stazioni che rilevano tali
parametri, e che posseggono serie storiche sufficientemente lunghe (a partire dal 1990
sino ad oggi). Le stazioni citate si trovano rispettivamente a sud-est e a nord-ovest del
bacino idrografico del lago
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
Expansion and specialization of agricultural systems in western mediterranean areas: A global analysis based on the two last census data
Full text linkThe study aims to describe and interpret the agricultural system dynamics on the Western Mediterranean areas in terms of occupied land and crop specialization, by using the available data from the two last agricultural censuses. From the spatial point of view, we chose to adopt the most detailed level available, by using the smallest land administrative unit (LAU) for every involved country (Spain, Portugal, France and Italy). The resulting database was made of about 16k records and seven fields for a total of 112k single data. The considered variables were: total farm area (TFA), utilized agricultural area (UAA), irrigated area (IA), arable lands (AL), permanent crops (PC), permanent grassland (PG) and remaining surface (RS). The LAU data analysis was carried out following the four steps: (i) level of land occupation by agricultural systems; (ii) patterns of crop groups in UAA composition; (iii) attribution to each LAU of an agricultural typology (AT), resulting from the combination of the two previous features and iv) calculation of two synthetic indices to evaluate the expansion and specialization level for each LAU. Finally, an analysis of the spatial distribution of the two indices was proposed. Results showed a lowering over time of the TFA, UAA and PG areas and an increase of IA and RS. The number of identified ATs was rising at the expense of their extension. This phenomenon led to a fragmentation in ATs spatial distribution within the same geographical region. These changes prove that farmers’ responses to the driving forces acting on agricultural systems have been more differentiated than in the past. The prevailing strategy seems to aim at a reduction in the level of specialization of the agricultural systems whereas less marked was the lowering of their level of expansion
Who Remains When Professional Farmers Give up? Some Insights on Hobby Farming in an Olive Groves-Oriented Terraced Mediterranean Area
No full textMany land use systems in Mediterranean sloping areas risk abandonment because of
nonprofitability, while their hydro-geological stability depends on an appropriate management.
However, who are the land managers? What are their practices? Our research on the traditional olive groves of the Monte Pisano (Tuscany, Italy) reveals for the first time the quantitatively important role of hobby farmers as land managers in the area. We used a three-step-method: first, a database
was constructed using several data sources to identify and map the population of olive growers; then, 35 semi-structured interviews were conducted, and finally, the data were analyzed to highlight the contribution of olive growers to the land management, along with their motivations and constraints.
Our results found that hobby farmers constitute about 90% of all land managers in the study area and manage more than half of the agricultural land. They are a very uneven group, and there are no clear categories detectable by analyzing sociodemographic factors, practices and farm characteristics.
They are the “same but different”, not following any market rules, as they are not profit-oriented.
Their farming practices are quite homogeneous and mainly in-line with professional farming practices of that area, oriented versus a minimum input management
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