• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 220
  • 177
  • 50
  • 26
  • 26
  • 26
  • 26
  • 26
  • 24
  • 12
  • 7
  • 5
  • 3
  • 3
  • 2
  • Tagged with
  • 592
  • 99
  • 98
  • 77
  • 70
  • 66
  • 64
  • 61
  • 57
  • 56
  • 54
  • 53
  • 53
  • 51
  • 48
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
121

Émissions d'ammoniac en provenance des infrastructures agricoles

Bluteau, Claudia January 2009 (has links)
Gaseous ammonia emissions from livestock production are a well known source of anthropogenic ammonia emissions and have been the subject of numerous studies in Western Europe and in the United States of America. They are deemed responsible for the acidification of ecosystems. Furthermore, ammonia emissions from intensive livestock operations located in the vicinity of major cities induce favourable conditions for smog formation. Ammonia volatilization from manure also reduces its effectiveness as a fertilizer by reducing its nitrogen content, an important nutrient for plant growth. Certain technologies and structures exist to cover manure storage tanks in order to limit these ammonia losses to the atmosphere. Very few studies have been done in Canada where climate and manure management practices differ widely from those in Western Europe and in the United States of America. In this project, a measurement campaign was financed by Agriculture and Agrifood Canada on four commercial livestock production infrastructure to begin the development of national ammonia inventory. Commercial dairy and swine manure storages covered by floating geomembranes were monitored for periods exceeding six months in the Eastern Townships of Quebec. The swine manure storage emitted negligible amounts of ammonia, from 5.9 ?10[superscript -3] to 0.14 [micro]g? m[superscript -2] . s[superscript -1] over the summer time. The dairy manure storage emitted more substantial amounts of ammonia when the manure surface was frozen in winter, from 1.9 to 16 [micro]g. m[superscript -2] ? s[superscript -1], then when unfrozen, 93 to 166 [micro]g? m[superscript -2] ? s[supercript -1]. A structural difference in the covering technology at the dairy manure storage rendered it less airtight than the swine manure storage. Therefore, the efficiency of a cover to limit ammonia emissions from manure is function of its air tightness. Ammonia emission rates from two tie-stall commercial dairy buildings were also monitored in the Eastern Townships of Quebec. Ammonia emission measurements done at building A during winter 2007 ranged from 3.77 to 6.80 g ? day[superscript -1] ? animal[superscript -1] while those performed at building B during summer 2007 were higher and ranged from 11.33 to 18.20 g ? day[superscript -1] ? animal[superscript -1]. These values fall within the wide range of those published for Western Europe and the United States of America. However, unlike studies completed in Europe using similar procedures, the methods used to measure gaseous ammonia concentrations and building ventilation flow rates in this study were validated in controlled environments.
122

Evaluating the impacts of biochar on the fate and dynamics of dairy manure in agricultural soil

Angst, Teri January 2013 (has links)
Biochar is a carbon sequestration technology that has shown potential to inhibit greenhouse gas (GHG) emission and nutrient leaching from soils, however the majority of biochar research thus far has focused on arable cropland rather than livestock systems or grasslands. Livestock production is an important agricultural system, and manure generated from livestock systems is a source of GHG emission as well as nutrient loading to surface- and groundwater. The high environmental impact of livestock production in the very areas that biochar has shown potential may suggest that this would be an ideal system for biochar incorporation. However, as grassland systems in the context of livestock production often receive high nutrient inputs in the form of manure which increases the potential for nutrient leaching or runoff, the high-nutrient ash content of biochar may potentially exacerbate this problem rather than suppress nutrient loss from soils. As private companies and government-funded programmes discuss the possibility of scaling the global manufacturing and soil-incorporation of biochar to a rate of gigatonnes per year, understanding the potential of biochar for use within a livestock system could be crucial in helping to develop an appropriate deployment plan for this material. This thesis is therefore focused on the use of biochar in grassland and livestock systems. It first examines the nutrient release from biochar in a sequential leaching experiment. Phosphorus (P) release indicated that provision of soil P (though quantitatively small) may be sustained over time whilst potassium (K+) release was quantitatively large but declined rapidly following the first extraction. An incubation study was then carried out using soil columns amended with farmyard manure, liquid manure (slurry) or fertiliser (plus an unamended control), each with and without biochar, which sought to determine the impact of biochar on N2O release and N and P leaching from soils with diverse nutrient sources. N2O emission from the columns was significantly suppressed by the presence of biochar, as was the leaching of mineral N. However, the amount of PO4 3--P in leachate was increased in biocharamended columns, relative to their unamended counter-parts. A slurry incubation study was then conducted, with a control slurry and four biochar-amended treatments, which explored whether biochar could suppress GHG and NH3 emission from manure prior to land application. The resulting data indicated that biochar demonstrates potential for GHG suppression but does not demonstrate potential for NH3 suppression from slurry in storage. Finally, a one-year field-based experiment was completed which analysed the impact of biochar on CH4, N2O, and NH3 emission as well as nutrient leaching from grassland soils that had been amended with a high rate of manure application (151.4 m3 ha-1 or 409 kg N ha-1). In this study, biochar demonstrated the potential to suppress each of the three types of gaseous emissions from manure-amended soil, though the differences between mean values were not statistically significant. Extracts from ion exchange resins indicated that annual cumulative K+ leached from biochar-amended plots was significantly higher than the control, and that P and NH4 + leached from biochar-amended plots was higher than the control at the time of the first rain event following biochar and manure application. Together, the results of these component studies indicate that biochar may indeed have potential to suppress GHG emissions from livestock systems, most likely through suppression of microbial activity by organic compounds that are sorbed to the char, though (as the mechanisms of GHG suppression by biochar are thus far not well understood) the capacity of biochar to do so may vary based on the type of biochar used, the soil characteristics, and other factors. Overall, the results of these studies suggest that some types of biochar should be used with caution in systems with high rates of nutrient application, unless the ash is removed prior to soil application.
123

Diversity and effect of the microbial community of aging horse manure on stable fly (Stomoxys calcitrans) fitness

Albuquerque, Thais Aguiar De January 1900 (has links)
Doctor of Philosophy / Department of Entomology / Ludek Zurek / Stable flies (Stomoxys calcitrans L.) are blood-feeding insects with a great negative impact on livestock resulting in annual losses around $2 billion in the USA alone. One of the main reasons for such an impact is because stable fly management is very difficult. Stable fly larvae develop primarily in animal manure and live bacteria were shown to be essential for stable fly development. I hypothesized that the microbial community of horse manure changes over time and plays an important role in stable fly fitness. Two-choice bioassays were conducted using 2 week old horse manure (control) and aging horse manure (fresh to 5 week old) to evaluate the effect of manure age on stable fly oviposition. The results showed that fresh manure did not stimulate oviposition and that the attractiveness increased as manure aged but started to decline after 3 weeks. Stable fly eggs artificially placed on 1, 2, and 3 week old manure resulted in significantly higher survival and heavier adults comparing to those developing in fresh, 4, and 5 week old manure. Analysis of the bacterial community of aging horse manure by 454-pyrosequencing of 16S rDNA revealed a major shift from strict anaerobes (e.g. Clostridium, Eubacterium, Prevotella, Bacteroidales) in fresh manure to facultative anaerobes and strict aerobes (e.g. Rhizobium, Devosia, Brevundimonas, Sphingopyxis, Comamonas, Pseudomonas) in 1-5 week old manure. Identified volatile compounds emitted from 2 and 3 week old horse manure included phenol, indole, p-cresol, and m-cresol. However, none of them stimulated stable fly oviposition in two-choice assays. In conclusion, the microbial community of 2 and 3 week old horse manure stimulates stable fly oviposition and provides a suitable habitat for stable fly development. Manure at this stage should be the main target for disrupting the stable fly life cycle. Volatile compounds acting as oviposition stimulants/attractants and their specific bacterial origin remain to be determined. Better understanding of stable fly microbial ecology is critical for development of novel management strategies based on alteration of the microbial community of stable fly habitat to generate a substrate that is non-conducive to fly oviposition and/or larval development.
124

AVALIAÇÃO DOS TEORES DE METAIS POTENCIALMENTE TÓXICOS NA MICROBACIA DO RIACHO BARRA GRANDE LOCALIZADA NO ENTORNO DO LIXÃO MUNICIPAL DA CIDADE DE IMPERATRIZ - MA.

Gama, Jullys Allan Guimarães 01 August 2013 (has links)
Submitted by admin tede (tede@pucgoias.edu.br) on 2016-08-17T14:44:32Z No. of bitstreams: 1 JULLYS ALLAN GUIMARAES GAMA.pdf: 1826371 bytes, checksum: 230f55a43f1d2ce1894678ed5b77b28c (MD5) / Made available in DSpace on 2016-08-17T14:44:32Z (GMT). No. of bitstreams: 1 JULLYS ALLAN GUIMARAES GAMA.pdf: 1826371 bytes, checksum: 230f55a43f1d2ce1894678ed5b77b28c (MD5) Previous issue date: 2013-08-01 / In the State of Maranhão, only three of the 217 municipalities have dump, the rest being made available only “dumpsters" as units of final disposal of solid waste. The municipality of Imperatriz-MA shares this reality, therefore, is for the municipal dump, which are sent every day all waste produced by the city, without any apparent worry or treatment. Starting this context, this study aimed to analyze the levels of potentially toxic metals, in the creek Barra Grande Watershed, a foremost tributary of the Tocantins River, located around the municipal dump, to evaluate the influence of the pollution effect of leach ate. Therefore, the methodology used was the type quantitative, exploratory and descriptive in nature. The main results showed that the leach ate currently generated is in methanogenic phase (ph = 8.3) and after infiltration and leaching processes, has contaminated streams and springs that are under its influence, and in view of the high concentration of Cu, Cr, Cd, Pb and Fe found in soil Cu and Cd and sediment chain Watershed. / No Estado do Maranhão, apenas três, dos 217 municípios, possuem aterro sanitário, sendo ao restante, disponibilizados apenas “lixões” como unidades de disposição final de resíduos sólidos. O município de Imperatriz-MA compartilha desta realidade, pois, é para o lixão municipal, que todos os dias são encaminhados todos os resíduos produzidos pela cidade, sem qualquer preocupação ou tratamento aparente. Partindo deste contexto, esta pesquisa teve por objetivo, analisar os teores de metais potencialmente tóxicos, na Microbacia do riacho Barra Grande, importante afluente do rio Tocantins, localizada no entorno do lixão municipal, visando avaliar a influência do efeito poluidor do chorume. Para tanto, a metodologia empregada foi do tipo quantitativa, exploratória e de natureza descritiva. Os principais resultados apontaram que, o chorume, atualmente, gerado, encontra-se em fase metanogênica (ph = 8,3) e que, após processos de infiltração e lixiviação, tem contaminado os córregos e nascentes que se encontram sob sua influência, tendo em vista os altos teores de Cu, Cr, Cd e Pb encontrados em água e em solo, e Cu e Cd, no sedimento corrente da Microbacia.
125

Utilisation of animal wastes and sewage sludges and their subsequent effects on higher trophic levels in food chains.

January 1981 (has links)
by Cheung Yun Hing Richard. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1981. / Bibliography: leaves 182-206.
126

Eficiência da utilização de adubos verdes em pomar de laranjeira 'Pêra' (Citrus sinensis (L.) Osbeck) /

Ragozo, Carlos Renato Alves, 1970- January 2005 (has links)
Orientador: Sarita Leonel / Banca: Sérgio Lázaro de Lima / Banca: João Domingos Rodrigues / Banca: José Eduardo Creste / Banca: José Orlando de Figueiredo / Resumo: O trabalho teve como objetivo avaliar a eficiência da utilização de adubos verdes em pomar de laranjeira 'Pêra' (Citrus sinensis (L.) Osbeck) e foi instalado na fazenda Três Irmãos, no município de Botucatu/SP. O solo da propriedade é denominado Neossolo Quartzarênico. As plantas estão enxertadas em limoeiro 'Cravo' e foram plantadas num espaçamento de sete por quatro metros, no ano de 1996, estando com sete e oito anos de idade respectivamente nos anos de 2003 e 2004, ocasião em que foi realizado o experimento. Foram empregados quatro tratamentos correspondentes aos adubos verdes avaliados, sendo eles: feijão de porco (FP) (Canavalia ensiformis DC), labe-labe (LL) (Dolichus lablab L.), feijão guandu anão (GA) (Cajanus cajan L. Millsp) e braquiária (BQ) (Brachiaria brizantha Hochst ex A. Rich. Stapf). Os adubos verdes foram semeados no mês de dezembro dos anos de 2003 e 2004, sendo ceifados e direcionados para a linha da cultura na ocasião do pleno florescimento, o que corresponde a cento e vinte dias após a semeadura dos mesmos. Adotou-se os mesmos tratos culturais indicados para a cultura, nos dois anos de experimentação. O delineamento experimental foi em blocos ao acaso com quatro tratamentos, seis repetições, duas plantas úteis para as avaliações, completamente rodeadas por plantas bordadura. As características avaliadas foram: análise química de solo nas linhas e entrelinhas da cultura, diagnose foliar, diagnóstico nutricional através do DRIS (Sistema Integrado de Diagnose e Recomendação), circunferência do tronco (cm), volume de copa (m3), índice relativo de clorofila (índice Spad), peso médio dos frutos (g) número de frutos por caixa, rendimento de suco (%), acidez total (g de ácido cítrico / 100g de polpa), sólidos solúveis totais (SS), ratio, produtividade, porcentagem de matéria seca dos adubos verdes...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The purpose of the experimental was to evaluate the efficiency of the use of the green manures on an orchard planted with orange (Citrus sinensis Osbeck) cv. 'Pera' and was carried out in a farm named 'Três Irmãos', situated in Botucatu/SP/Brazil. The soil is Oxic Quartzipsamments. Plants are grafted on 'Cravo' lemon tree and were planted spaced 7 x 4 m apart, in 1996, and were seven and eight years old in 2003 and 2004, respectively when the experiment was conducted. Four different treatments were applied corresponding to the three green manures: jack bean (FP) (Canavalia ensiformis DC), lab-lab (LL) (Dolichus lablab L.), dwarf guandu (GA) (Cajanus cajan L. Millsp) and brachiaria (BQ) (Brachiaria brizantha Hochst ex A. Rich. Stapf) as a control. They were sown on December, 2003 and 2004, being mowed and directed to the line plants by the occasion of the full flowering, wich happened one hundred and twenty days after sowing. The same treatments were utilized in both experimental years. The experimental design was a randomized blocks with four treatments, six replications, and two useful plants per plot. Characteristics evaluated were: chemical analysis of the soil over the planting lines and in the middle of the citrus orchard rows, chemical analysis of the leaves, nutritional diagnosis through the DRIS, trunk circumference (cm), volume of the canopy (m3), relative index of chlorophyll (SPAD index), average fruits weight (g), number of fruits per boxes, juice content (%), total acidity (g of citric acid / 100 g of pulp), total soluble solids, ratio, productivity, percentage of dry matter and the contents of macro and micronutrients in the green manures and control (BQ). The results obtained allowed the following conclusions: the nutritional diagnosis elaborated through DRIS showed...(Complete abstract click electronic access below) / Doutor
127

The Effect of Different Methods of Handling Chicken Manure on the Viability of Weed Seed

Stoker, Golden L. 01 May 1938 (has links)
It is well known that weeds spread and are perpetuated by means of seed and vegetative reproduction. The seeds in turn are spread by various agencies such as wind, water, animals and man. These agencies are aided by especially adapted seed mechanisms for dissemination.
128

Response of nitrogen and phosphorus leaching and soil properties to applications of biosolids during turfgrass establishment

Kerns, James Patrick 17 February 2005 (has links)
Regulations for total maximum daily loads require management of phosphorus loading from farms and municipalities. This study evaluated environmental impacts of a system for using and exporting the phosphorus in composted dairy manure (CDM) and composted municipal biosolids (CMB) through turfgrass sod. Responses of soil physical, chemical, and biological properties within and below the sod layer were monitored during turfgrass establishment in two experiments under greenhouse conditions. During turf establishment in column lysimeters, phosphorus and nitrogen leaching from an amended surface layer through soil were evaluated. In addition, growth of turf was related to the observed changes in soil nutrients and properties. In the first experiment, four replications of a factorial design comprised three soil types (USGA greens sand, Windthorst fine sandy loam [fine, mixed, thermic Udic Paleustalf], Houston black clay [fine, smectitic, thermic, Udic Hapustert]), two dairy manure rates ( 200 kg P ha-1, 400kg P ha-1), and two turf species (St. Augustinegrass (Stenotaphrum secundatum [Walt.] Kuntze var. Raleigh) and Tifway 419 Bermudagrass (Cynodon dactylon [L.] Pers. x C. transvaaleensis Burtt-Davy). Columns received three separate leaching events in which a 9-cm depth of distilled water was applied. A similar experimental design was implemented for Experiment 2 in January 2004. Treatments consisted of the same three soils and three volume-based rates of CDM and CMB (0, 150, 250 cm3 L-1) during establishment of St. Augustinegrass turf. Columns received one pore volume of distilled water on three separate occasions. In both experiments, soil physical properties (bulk density, water infiltration rate, and water content) and microbial populations were unaffected by CDM or CMB. Applications of CDM at P-based rates utilized in the first experiment yielded no variation of leaching loss among rates of P or N. Most of the P applied was retained in the top 10 cm of soil. When large volume-based rates were used, leaching losses of P and N varied among CDM or CMB application rates. Leaching losses were only observed in the USGA sand and were highest for the 250 cm3 L-1 rate of CDM or CMB. Regardless of compost source, applications of organic amendments at volume-based rates can increase leaching loss of P and N on sandy soils. However, if P-based rates are used there is little risk for leaching loss of N and P during sod establishment.
129

Phosphorus reduction in dairy effluent through flocculation and precipitation

Bragg, Amanda Leann 17 February 2005 (has links)
Phosphorus (P) is a pollutant in freshwater systems because it promotes eutrophication. The dairies in the North Bosque and its water body segments import more P than they export. Dairies accumulate P-rich effluent in lagoons and use the wastewater for irrigation. As more P is applied as irrigation than is removed by crops, P accumulates in the soil. During intense rainfall events, P enters the river with stormwater runoff and can become bio-available. Reducing the P applied to the land would limit P build up in the soil and reduce the potential for P pollution. Since wastewater P is associated with suspended solids (SS), the flocculants, poly-DADMAC and PAM, were used to reduce SS. To precipitate soluble P from the effluent, NH4OH was added to raise the pH. Raw effluent was collected from a dairy in Comanche County, TX, and stored in 190-L barrels in a laboratory at Texas A&M University. Flocculant additions reduced effluent P content by as much as 66%. Addition of NH4OH to the flocculated effluent raised the pH from near 8 to near 9, inducing P precipitation, further reducing the P content. The total P reduction for the best combination of treatments was 97%, a decrease from 76 to 2 mg L-1. If this level of reduction were achieved in dairy operations, P pollution from effluent application would gradually disappear.
130

Lincomycin and Spectinomycin : persistence in liquid hog manure and their transport from manure-amended soil

Kuchta, Sandra Louise 03 March 2008
Antimicrobials administered to livestock can be excreted up to 80% in the feces and urine. Liquid swine manure from confined animal feeding operations is generally retained in lagoon storage until it is applied as a nutrient source to cropland. Thus, the applied manure becomes a possible source of antimicrobials to aquatic ecosystems. Veterinary antimicrobials have been detected in surface and ground waters in Canada, the United States and Europe, however, their environmental fate is not well known. Lincomycin and spectinomycin are two antimicrobials administered as a mixture to swine in the prairie region of Canada for the prevention of post-weaning diarrhea. In order to assess the potential for contamination of prairie wetlands, concentrations of both antimicrobials were monitored in the liquid manure from the nursery area of a commercial-scale barn during a 5-week study, and their persistence during simulated manure storage investigated. The potential for transport of lincomycin and spectinomycin to surface waters via surface runoff and to leach to groundwater was also assessed. This was achieved by monitoring manure-amended soil, simulated rainfall runoff, snow melt runoff and groundwater over a two-year period at two study sites in Saskatchewan, Canada following fall application of liquid swine manure from two commercial barns to crop and pasture land. Liquid chromatography coupled with tandem mass spectrometry was used to quantitate these antimicrobials in all matrix extracts. <p>In the nursery area of a commercial-scale barn, concentrations of lincomycin and spectinomycin in the cumulating liquid manure at the end of the study were equivalent to 32 and 3.0%, respectively, of doses administered in the feed. In a laboratory study, using fortified liquid manure, concentrations of both antimicrobials showed a rapid initial decrease during simulated lagoon storage, followed by a slower dissipation over a period of 5 months. The average time required for 50% dissipation of lincomycin was greater than one year (365 d) and was approximately 90 d for spectinomycin. <p>Lincomycin concentrations in soil (46.3 to 117 µg kg-1) collected immediately after fall manure application, decreased to non-detectable levels by mid-summer the following year. Lincomycin was present in simulated rainfall runoff (0.1 to 2.7 µg L-1) immediately after manure application with similar concentrations present in snow meltrunoff the following spring. Concentrations in groundwater were generally <0.005 µg L-1. Spectinomycin was not detected in the manure applied at the study sites nor in soil, runoff water or groundwater samples. This study confirms that some antimicrobials, including lincomycin, may be present in lagoon manure. Thus, the management practice of utilizing livestock manure from confined animal feeding operations as a plant nutrient source on cropland may result in antimicrobial transport to surface and ground waters.

Page generated in 0.0524 seconds