1,721,066 research outputs found
Data Set for GIS-based multi-criteria analysis for Arabica coffee expansion in Rwanda
No full text<p>This project file contains row research data and result data that have been used for the paper entitled "GIS-based multi-criteria analysis for Arabica coffee expansion in Rwanda" by Innocent Nzeyimana, Alfred E. Hartemink, Violette Geissen. </p>
<p>http://dx.doi.org/10.6084/m9.figshare.1128594- See more at: http://figshare.com/preview/_preview/1128594#sthash.QkGK7m8Y.dpuf</p
Efecto de suelos quemados sobre las lombrices de tierra (Oligochaeta) y la fertilidad del suelo en plantaciones de Eucalyptus grandis
No full textSan Francisco de Campeche, Campeche, México : El Colegio de la Frontera Sur, 2013
Contenido de Etilentiourea (ETU), primer metabólito del fungicida Mancozeb, en los sedimentos y aguas de los drenes en la zona platanera de Teapa, Tabasco
Full text linkResumen en español: "La posible acumulación del principal metabolito ETU, Mn y Zn a causa de la constante aplicación del fungicida Mancozeb, fueron estudiados en los sedimentos y aguas superficiales de los drenes de la zona platanera de Teapa, Tabasco. En los sedimentos, se determinaron el contenido de ETU, los metales pesados de Mn y Zn. En el agua, se determino la concentración de ETU. Las propiedades físicas y químicas se determinaron en sedimentos y agua, con la finalidad de relacionar estás características con el contenido de cada compuesto encontrado. Se realizaron muestreos en dos temporadas (sequía y lluvias). En la temporada de sequía, los sedimentos fueron tomados en los drenes de las 6 fincas con un total de 54 muestras cubriendo un área de 800 ha. En la temporada de lluvias, se trabajo con 1 finca, en la que se tomaron muestras de sedimento y agua en los mismos puntos y drenes del primer muestreo. Adicionalmente, se tomaron muestras de agua del arroyo Sauz que sirve como receptor del sistema de flujo hidráulico de la finca. En ambas temporadas, el contenido de ETU de los sedimentos se encontraron cerca y por debajo del limite de detección (0.01 mg kg-1), lo que no represento ninguna acumulación. Sin embargo, los contenidos de Mn en los sedimentos de todos los sitios excedieron el valor umbral para la vida acuática (630 mg kg-1 Long et al., 1995) con valores entre 635 a 7256 mg kg-1 Los contenidos de Zn en los sedimentos variaron desde 87 a 190 mg kg-1 excediéndose por arriba del valor umbral para la vida acuática (98 mg kg-1 Long et al., 1995) en varios sitios. Además, se estimo la acumulación de estos metales pesados en los sedimentos de la zona platanera en comparación con potreros que fueron tomados como referencia. En contraste con el bajo contenido de ETU en los sedimentos, la concentración en el dren y el arroyo (5.9-13.8 μg L-1) excedieron los valores permisibles para agua potable. (0.1 μg L-1) establecido por la European Commission en (1998).
Pesticide use and off-site risk assessment : a case study of glyphosate fate in Chinese Loess soil
Full text linkPesticide use and off-site risk assessment: a case study of glyphosate fate in Chinese Loess soil Xiaomei Yang Abstract: Repeated applications of pesticide may contaminate the soil and water, threatening their quality within the environmental system and beyond it through water erosion related processes and leaching. Taking into account the situation of intense farming, pesticide use and erosion in China, and in the loess area in particular, this study aims to further the science of pesticide risk assessment by increasing the understanding of the fate of glyphosate and its main metabolite AMPA while also assessing their risks related to soil erosion in Chinese loess soil. Four main objectives are conducted: 1) Assessment of farmers’ knowledge and awareness of pesticide use in the Wei River catchment In this study, we presented the information for the knowledge and awareness of pesticide risks via face-to-face interview among farmers (209) and retailers (20) in two rural regions (Qianyang County (S1) and Chencang County (S2)) of the Wei River catchment in China where the modes of farming and the state of erosion are very different. The results showed that farmers learned about the use and risk related to of pesticide use mainly by oral communication (p70%) was the most common mode of personal hygiene after spraying, comparing to wearing masks, showering, and changing clothes. Regarding to dealing with the packages or containers of pesticide, farmers dumped them directly onto the land or into water, and over 85% of farmers claimed to use illegal pesticides. Compared to farmers, pesticide retailers were well-informed and highly conscious of their responsibility for the safe use of pesticides. Educational programmes targeted to age groups, proper disposal of pesticide waste, and sufficient supervision from authorities should consequently be considered for improving the levels of knowledge and awareness of the dangers of pesticides to human health and environmental pollution in the Wei River catchment, China. 2) Investigation of off-site transport of glyphosate and AMPA by runoff and erosion in Chinese loess soil In this study, we assessed the short-term transport (1h duration, 1 mm min-1 rainfall) of glyphosate and its metabolite aminomethylphosphonic acid (AMPA) related to erosion and runoff on bare loess soil with different slopes (10° and 20°)and application rates (3.6 kg ha-1 and 7.2 kg ha-1) in hydraulic flumes. Significant power and exponent function described a significantly negative relation between rainfall duration and the content of glyphosate and AMPA (pp 3) Investigation of the on-site fate of glyphosate and AMPA formation in Chinese loess soil In this study, we observed glyphosate decay, erosion and runoff related transport of glyphosate and AMPA at different slopes (10° and 20°) and application rates (3.6 kg ha-1 and 7.2 kg ha-1) under field condition during 35 d, September-October in 2012 (16.8±2.1°C with 35 mm rainfall in total) and July-August in 2013 (27 ± 2.3°C with 74 mm rainfall in total). The initial glyphosate decayed rapidly (half-life of 3.5 d) in the upper 2 cm of soil following a first-order rate of decay. AMPA content in the 0-2 cm soil layer correspondingly peaked 3 d after glyphosate application and then gradually decreased. The residues of glyphosate and AMPA decreased significantly with soil depth (p 4) Off-site risk assessment of particle-facilitated pesticide transport related to erosion In this study, we have developed a parsimonious integrative model of pesticide displacement by runoff and erosion that explicitly accounts for water infiltration, erosion, runoff, and pesticide transport and degradation in soil. The conceptual framework was based on broadly accepted assumptions such as the convection-dispersion equation and lognormal distributions of soil properties associated with transport, sorption, degradation, and erosion. To illustrate the concept, a few assumptions are made with regard to runoff in relatively flat agricultural fields: dispersion is ignored and erosion is modelled by a functional relationship. A sensitivity analysis indicated that the total mass of pesticide associated with soil eroded by water scouring increased with slope, rain intensity, and water field capacity of the soil. The mass of transported pesticide decreased as the micro-topography of the soil surface became more distinct. The timing of pesticide spraying and rate of degradation before erosion negatively affected the total amount of transported pesticide. The mechanisms involved in pesticide displacement, such as runoff, infiltration, soil erosion, and pesticide transport and decay in the topsoil, were all explicitly accounted for, so the mathematical complexity of their description can be high, depending on the situation. Overall, the outcome of this study indicates that it is urgent to improve farmers knowledge and awareness on pesticide use in order to reduce pesticide risks before they are applied in environmental system. The rapid decay of glyphosate to AMPA in loess soil suggests that on-site risks of glyphosate is mainly related to AMPA, especially under warmer climatic conditions. The off-site transport of glyphosate in our study was about 14% of the applied dose after 1 h of rainfall indicating that the off-site risks of glyphosate should be taken into account in regions highly prone to soil erosion. The concept of particulate transport elaborated in objective 4 should be incorporated in existing erosion models, such as LISEM, to predict off-site effects of glyphosate applications. </p
Degradación y transporte de etilentiourea (ETU) en suelo y agua de una zona tropical del sureste de México
Full text linkResumen en español: "En la zona del trópico de México, se usan productos principalmente a base del ingrediente activo mancozeb, para el control de Sigatoka negra, en el cultivo del banano. Se hacen aproximadamente 52 aplicaciones anuales, usando una dosis de 2.5 kg ha-1.Uno de los productos de degradación del mancozeb es el etilentiourea (ETU), el cual es considerado como un posible contaminante ambiental. Con el objetivo de conocer la persistencia, movilidad y efecto de etilentiourea (ETU), se hicieron ensayos en suelo y agua, simulando condiciones de una zona tropical. Se encontró que 1 mg kg-1 de ETU en suelo activo, tuvo una vida media de 1.5 h y que fue degradado totalmente en menos de 24 h. El contenido inicial de ETU producido de mancozeb (20.8 mg kg-1) en suelo activo, estuvo por debajo del límite de detección (0.006 mg L-1) en la 120 h, al degradarse principalmente por vía biológica. Por otro lado, no hubo diferencia significativa en la degradación de la concentración inicial de 2.38 mg L-1 de ETU, en agua activa y estéril, la vida media fue 115.52 y 99.02 h, respectivamente. Lo anterior indica que la principal vía de degradación de ETU en agua fue la hidrólisis, la cual no ha sido reportada anteriormente como vía principal de degradación. Al hacer el estudio del movimiento de ETU en suelo, el metabolito no fue detectado en el suelo y ni en el lixiviado, debido a que tuvo un efecto de dilución en el suelo. El mancozeb y el ETU no tuvieron efecto en la respiración del suelo al tener una tasa de producción de CO2 de 46.99 y 47.21 mg CO2 kg-1 d-1 en suelo activo con y sin mancozeb, respectivamente. Los resultados indican que bajo condiciones de una zona tropical, ETU a partir de mancozeb no representa riesgo de acumulación en suelo ni en aguas subterráneas, mientras que para los acuíferos el metabolito podría representar un riesgo de contaminación.
Optimizing soil and water management in dryland farming systems in Cabo Verde
No full text<strong> “Optimizing Soil and Water Management in Dryland Farming Systems in Cabo Verde”</strong> Isaurinda Baptista <strong>Summary</strong> Soil and land degradation poses a great challenge for sustainable development worldwide and, in Cabo Verde, has strongly affected both people’s livelihood and the environment. Dryland food production in Cabo Verde faces steep slopes, inadequate practices, irregular intense rain, recurrent droughts, high runoff rates, severe soil erosion and declining soil fertility, leading to the inefficient use of rainwater. Despite the enormous investment in soil and water conservation measures (SWC), land degradation due to water erosion is still rife and dryland crop productivity remains low. Sustainable land management (SLM) techniques that reduce runoff, erosion and nutrient loss are the key to mitigating/preventing land degradation and assuring long-term soil productivity. This thesis investigated soil and water management techniques for Cabo-Verdean dryland farming systems to increase the efficiency of rainwater and crop yield, combining traditional and scientific knowledge in a field-based participatory approach. Field experiments were conducted in different agro-ecological zones of the Santiago Island aiming to evaluate the effects of water conservation techniques (mulching of crop residue, soil surfactant and pigeon-pea hedges) combined with organic amendments (compost and animal or green manure) on runoff, erosion, soil nutrients and crop yield. The PESERA-DESMICE modelling approach allowed assessing the biophysical and socio-economic benefits of the promising SLM techniques against a local baseline condition and their potential application at larger scale, under climate variability. Following the general introduction (chapter 1), chapter 2 of the thesis reviews the national strategies towards building resilience against the harsh environmental conditions, analyses the state of land degradation and its drivers, surveys the existing SWC measures, and assesses their effectiveness against land degradation and in supporting people’s livelihoods. The analysis allows inferring that the relative success of Cabo Verde in tackling desertification and rural poverty is due to an integrated governance strategy that comprises awareness raising, institutional framework development, financial resource allocation, capacity building, and active participation of rural communities. The chapter provides a panoramic view of the importance of SWC measures for Cabo Verde drylands and recommends further specific, science-based assessment of the biophysical and socioeconomic impact of SLM and potential for upscaling. Chapter 3, first, discusses the participatory approach used in selecting the SLM techniques that are field-tested in this research and, then, evaluates the effects of the selected water conservation techniques combined with organic amendments on the generation of runoff and soil loss from rain-fed agricultural fields compared with traditional farmers’ practices. The chapter also discusses the main factors influencing runoff and soil loss in semiarid dryland hilly areas, including the degree of soil cover, rainfall amount and erosivity, slope and soil infiltration rate. Runoff was significantly reduced only with the treatments containing mulch on slopes >10% and in the treatment containing surfactant and organic amendment on slopes <10%. Observed soil erosion rates were highest for the silty-clay-loam soil, followed by the sandy-loam soil and the loamy-soil, reaching a maximum value of 17 Mg ha-1 in the traditional practice, but were reduced by more than 50% with the SLM techniques. Residue mulch and pigeon-pea combined with an organic amendment (T3) almost eliminated runoff and erosion from agricultural fields even on steep slopes, contributing to improved use of rainwater at the plot level. The chapter recommends that SLM techniques, such as T3, be advocated and promoted for the semiarid hillsides of Cabo Verde prone to erosion to increase rainwater-use and to prevent further soil degradation. As soil erosion, runoff and related nutrient losses constitute a high risk to soil fertility in Cabo Verde drylands, chapter 4 focuses on the effects of the techniques tested in chapter 3 on erosion and runoff related nutrient losses (NO3-N and PO4-P) and on crop productivity. The traditional system lost significantly higher amounts of both NO3-N and PO4-P than the tested SLM techniques, with the T3 technology reducing soil loss, runoff and nutrient losses to nearly a 100%. Nutrient losses from the amended plots were low, while the significant losses from the traditional system could result in long-term nutrient depletion in the soil. The treatments did not consistently increase crop yield or biomass in all three sites, but the combination of organic amendment with soil surfactant increased both crop yield and biomass in some cases. T3 was the best treatment for steep slope areas, although it is crucial to manage the pigeon-pea hedges to achieve higher maize yield. For flatter areas with deeper soils, the combination of organic amendment with soil surfactant could be a less expensive and effective choice. The chapter identifies and recommends SLM techniques to prevent nutrient depletion, improve dryland crop yield and avoid further land degradation due to erosion by water, both in steep slope areas and flatter areas. Given the potential of the SLM techniques, but also significant spatial-temporal yield variability, chapter 5 considers the PESERA-DESMICE modelling approach to capture a greater range of climatic conditions and evaluate the biophysical and socio-economic benefits of the promising SLM technique (residue mulch combined with pigeon-pea hedges and an organic amendment - T3) against the traditional baseline practice of maize-bean intercropping (T0). It also evaluates the potential for upscaling the selected technique at Island scale. From stations in semi-arid and sub humid climates, long-term historic rainfall statistics allowed construction of 50-year rainfall realizations providing a unique time-series of rainfall scenarios and an envelope of the potential biomass production. T3 elevates yield under both sub-humid and semi-arid climates with greater security for sub-humid areas even though risk of crop failure still exists. The T3 technology offered good potential to increase yields by 20% in 42% of the area and reduce erosion by 8.6 Mg ha-1, but in terms of cost effectiveness, it might be prohibitively expensive for farmers lacking inputs. Such findings can inform policy options or influence adoption of conservation measures under the climatic variability of the Cabo Verde drylands and resilience to future climate change. The thesis ends with a synthesis chapter (6) that presents the research findings, highlights the new contributions made to the current scientific debates on Climate-Smart Agriculture (CSA) technologies for sub-Saharan Africa, sustainable intensification and land degradation neutrality. The T3 technology can be a promising CSA practice that could be widely used by smallholder farmers in semiarid regions to maintain food production and secure farmers’ livelihoods, while contributing to ecosystem services by storing water in the soil. The synthesis concludes with policy recommendations for optimizing soil and water management on hilly drylands to prevent further degradation. Hence, the thesis presents options to support moving from degrading and low yielding land management practices towards more sustainable land intensification in hilly drylands that reduce runoff and soil loss, increase crop nutrient and crop productivity, ultimately, contributing to the mitigation/adaptation of climate change, food security and land degradation neutrality in Cabo Verde
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
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