• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 17
  • 15
  • 10
  • 7
  • 1
  • Tagged with
  • 62
  • 20
  • 11
  • 9
  • 8
  • 8
  • 7
  • 7
  • 7
  • 7
  • 7
  • 6
  • 6
  • 6
  • 6
  • 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.
21

Propiedades químicas de suelo en líneas de piedra con Atriplex nummularia Lindl. y aplicación de estiércol de caprino en una ladera degradada de la Región de Coquimbo / Soil chemical properties at stone lines with Atriplex nummularia Lindl. and goat manure applications on a degraded hillside at the Coquimbo Region

Gacitúa Fefer, Camila Paz January 2017 (has links)
Memoria para optar al Título Profesional de Ingeniera Agrónoma / El presente estudio busca evaluar los eventuales cambios en las propiedades químicas de un suelo en condición de ladera con severos signos de degradación, sometido a un sistema de cosecha de agua de lluvia (líneas de piedra). Durante el año 2011, se construyeron 3 líneas de piedra junto con el establecimiento de Atriplex nummularia Lindl. y aplicación de estiércol de caprino (4 Mg ha-1). Para dos temporadas, 2014 y 2015, se evaluaron pH, conductividad eléctrica (CE), materia orgánica (MO) y macronutrientes totales (NPK); además se determinó el crecimiento (altura y masa seca total) y NPK tanto en hoja como en tallo de las plantas. El estiércol en general mostró un aumento significativo pero temporal en el pH, el contenido de MO y NPK evaluados en los suelos. Además, se observaron incrementos de CE en la superficie del suelo, siendo asociados a la caída de las hojas de la planta. Se aprecia un menor crecimiento de A. nummularia bajo la línea de piedra y, aunque sin diferencias significativas, el crecimiento fue levemente mayor en el tratamiento con estiércol animal, al igual que para los NPK medidos en la planta. El mayor crecimiento vegetal sobre la línea de piedra, contribuye directamente a la protección del suelo contra los procesos de erosión dominantes. Además, la incorporación del estiércol de caprino generó un mejoramiento en las propiedades químicas de suelo evaluadas, pero su efecto al ser temporal determina que es necesario considerar un plan de aplicaciones periódicas para obtener un efecto prolongado en el tiempo.
22

Evaluación de fitorremediación de suelos contaminados con plomo mediante el cultivo de Atriplex halimus L. / Evaluation of phytoremediation of polluted soils with lead by culturing of Atriplex Halimus L.

Queupuan Colil, Millaray Elba January 2017 (has links)
Memoria para optar al título profesional de Ingeniero Agrónomo / En la actualidad, la preocupación por el efecto de los elementos traza metálicos ha ido en aumento debido a su persistencia, a su acumulación progresiva en distintos medios naturales y fundamentalmente, por el efecto tóxico que manifiestan en pequeñas concentraciones, llegando a ocasionar problemas en ecosistemas y en la salud humana. Uno de ellos, el plomo, es uno de los elementos que constituye el grupo de los elementos traza metálicos, no esencial y contaminante ambiental. Para disminuir el impacto de suelos contaminados, se emplea la técnica de fitorremediación que implica la utilización de plantas capaces de contener, extraer o reducir los contaminantes a través de la acción de las raíces y su microflora. Además, complementariamente, se utilizan agentes quelantes, que tienen como propósito aumentar la biodisponibilidad de metales en el suelo. El presente trabajo tiene como objetivo aplicar la fitorremediación inducida como estrategia de mitigar la contaminación de suelos por plomo mediante el cultivo de Atriplex halimus L.
23

Palatability variation between the sex phenotypes of bladder saltbush (Atriplex vesicaria)

Maywald, Dionne Lee. January 1998 (has links) (PDF)
Bibliography: leaves 105-121. This study reports the first thorough investigation of palatability variation in Atriplex vesicaria Heward ex Benth. (bladder saltbush). Intensive small-plot dietary trials, supported by a paddock dietary experiment, cross-fence comparisons and cafeteria trials, showed that sheep preferentially grazed female saltbushes over male and bisexual ones. Sheep avoided male saltbushes due to a chemical deterrent, and used visual (male flower spike) and olfactory cues to detect male plants. The effect of this selective grazing was to reduce the size and reproductive output of female shrubs. Sheep also tended to return to shrubs they had grazed previously. In the semi-arid regions of South Australia, where bladder saltbush is grazed year-round, physical protection is recommended to maximise survival and reproductive output of heavily grazed shrubs.
24

Palatability variation between the sex phenotypes of bladder saltbush (Atriplex vesicaria) / by Dionne Lee Maywald.

Maywald, Dionne Lee January 1998 (has links)
Includes bibliographical references (leaves 105-121) / x, 121, [39] leaves : ill., maps ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Investigates the palatability variation in Atriplex vesicaria Heward ex Benth. (bladder saltbush). The main aim of the research was to examine the idea that the sex phenotypes of this species differ in their palatability to sheep, and to characterise some of the temporal and spatial features of the phenomenon. Intensive small-plot dietary trials, supported by a paddock dietary experiment, cross-fence comparisons and cafeteria trials, showed that sheep preferentially grazed female saltbushes over male and bisexual ones. Sheep avoided male saltbushes due to a chemical deterrent, and used visual (male flower spike) and olfactory cues to detect male plants. The effect of this selective grazing was to reduce the size and reproductive output of female shrubs. Sheep also tended to return to shrubs they had grazed previously. In the semi-arid regions of South Australia, where bladder saltbush is grazed year-round, physical protection is recommended to maximise survival and reproductive output of heavily grazed shrubs. / Thesis (Ph.D.)--University of Adelaide, Depts. of Environmental Science & Management and Botany, 1999?
25

Palatability variation between the sex phenotypes of bladder saltbush (Atriplex vesicaria) / by Dionne Lee Maywald.

Maywald, Dionne Lee January 1998 (has links)
Includes bibliographical references (leaves 105-121) / x, 121, [39] leaves : ill., maps ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Investigates the palatability variation in Atriplex vesicaria Heward ex Benth. (bladder saltbush). The main aim of the research was to examine the idea that the sex phenotypes of this species differ in their palatability to sheep, and to characterise some of the temporal and spatial features of the phenomenon. Intensive small-plot dietary trials, supported by a paddock dietary experiment, cross-fence comparisons and cafeteria trials, showed that sheep preferentially grazed female saltbushes over male and bisexual ones. Sheep avoided male saltbushes due to a chemical deterrent, and used visual (male flower spike) and olfactory cues to detect male plants. The effect of this selective grazing was to reduce the size and reproductive output of female shrubs. Sheep also tended to return to shrubs they had grazed previously. In the semi-arid regions of South Australia, where bladder saltbush is grazed year-round, physical protection is recommended to maximise survival and reproductive output of heavily grazed shrubs. / Thesis (Ph.D.)--University of Adelaide, Depts. of Environmental Science & Management and Botany, 1999?
26

The distribution and abundance of nematodes (especially the plant parasites) in the arid region of South Australia /

Nobbs, J. M. January 1987 (has links) (PDF)
Thesis (Ph. D.)--University of Adelaide, Dept. of Plant Pathology, 1987. / Includes bibliographical references.
27

Winterfat seed viability and dormant season livestock grazing /

Leary, Ryan. January 1900 (has links)
Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 39-44). Also available on the World Wide Web.
28

Contribuição de solutos orgânicos e inorgânicos no potencial osmótico de folhas de atriplex nummularia submetidas ao NaCl, SECA E PEG. / Contribution of organic and inorganic solutes in the osmotic potential of leaves of Atriplex nummularia submitted to NaCl, DROUGHT AND PEG.

Brilhante, Jean Carlos de Araújo January 2006 (has links)
BRILHANTE, J. C. A. Contribuição de solutos orgânicos e inorgânicos no potencial osmótico de folhas de atriplex nummularia submetidas ao NaCl, SECA E PEG. 2006. 195 f. Dissertação (Mestrado em Agronomia/Fitotecnia) - Centro de Ciências Agrárias, Universidade Federal do Ceará, Fortaleza, 2006. / Submitted by Francisco Lacerda (lacerda@ufc.br) on 2014-07-15T19:39:06Z No. of bitstreams: 1 2006_dis_jcabrilhante.pdf: 1463347 bytes, checksum: 7f27bb350d9b7a07d32ec4ecef65c90f (MD5) / Approved for entry into archive by José Jairo Viana de Sousa(jairo@ufc.br) on 2014-07-16T20:06:44Z (GMT) No. of bitstreams: 1 2006_dis_jcabrilhante.pdf: 1463347 bytes, checksum: 7f27bb350d9b7a07d32ec4ecef65c90f (MD5) / Made available in DSpace on 2014-07-16T20:06:44Z (GMT). No. of bitstreams: 1 2006_dis_jcabrilhante.pdf: 1463347 bytes, checksum: 7f27bb350d9b7a07d32ec4ecef65c90f (MD5) Previous issue date: 2006 / Uma das características fisiológicas mais importantes das halófitas pertencentes ao gênero Atriplex é a enorme habilidade de acumular solutos orgânicos e inorgânicos com o intuito de se ajustar osmoticamente em condições de elevada salinidade e deficiência hídrica. Contudo estudos compreensivos sobre a contribuição relativa desses solutos inorgânicos e orgânicos no ajustamento osmótico de folhas dessas halófitas ainda são poucos explorados na literatura. Esse trabalho pretende pela primeira vez na literatura fazer um estudo detalhado, da participação e da contribuição relativa da maioria dos solutos orgânicos e inorgânicos no potencial osmótico de folhas de Atriplex nummularia, submetidas a concentrações crescentes de NaCl, ciclos sucessivos de seca e ao polietileno glicol (PEG). Para responder as questões acima mencionadas foram conduzidos três grandes experimentos seqüenciais. No primeiro experimento, mudas de Atriplex nummularia com quatro meses de idade, foram cultivadas em vasos de argila contendo como substrato areia, sendo irrigadas a cada dois dias com solução contendo concentrações crescentes de NaCl (0, 100, 200, 300 e 400 mmol L-1) durante 120 dias. O experimento foi realizado em condições de casa de vegetação. No segundo experimento, mudas de A. nummularia, com idade de 18 meses foram transplantadas para recipientes de polietileno contendo 5.0 kg de vermiculita, em condições de casa de vegetação, onde foram submetidas aos seguintes tratamentos (Controle; seca; NaCl + seca; NaCl) por três ciclos sucessivos de seca-reidratação (3 semanas) seguido de uma recuperação no final do último ciclo (após 48 h). No terceiro experimento, plântulas de A.nummularia, com idade de dois meses foram transplantadas para cultivo hidropônico em vasos plásticos com capacidade para 0,8 em sala de crescimento sob condições controladas onde sofrerão um pré-condicionamento com ou sem NaCl por duas semanas. Após foram submetidas aos seguintes tratamentos (controle; PEG; NaCl; NaCl + PEG). Em conclusão, os resultados da presente investigação demonstram que as plantas de Atriplex nummularia foram capazes de manter o seu crescimento mesmo em condições de alta salinidade, principalmente pela capacidade de manutenção de seu status hídrico. Os resultados também sugerem que a GB é o maior soluto orgânico envolvido com o ajustamento osmótico (AO) do citoplasma e que sua acumulação parece ser uma resposta adaptativa ao estresse provocado pelo NaCl. Em adição, o íons salinos Na+ e Cl- contribuíram para a maioria do AO das folhas submetidas ao NaCl. O impacto relativo do K+ sobre o AO das folhas foi reduzido consideravelmente com o aumento da dose externa de NaCl. Os resultados evidenciam também que o pré-condicionamento com NaCl influenciou positivamente no crescimento de Atriplex nummularia, em condições de seca, evidenciado pelo maior acúmulo de massa seca e melhor status hídrico das folhas. Dentre os solutos inorgânicos analisados, o Na+ e o Cl- foram os que mais contribuíram para a osmorregulação das folhas em condições de deficiência hídrica. Enquanto, GB foi o soluto orgânico mostrou o maior percentual de contribuição para o potencial osmótico. Entretanto os resultados mostraram que o pré-condicionamento das plântulas de Atriplex nummularia com NaCl não foram capazes de atenuar os efeitos induzidos pelo PEG.
29

Utilização de atriplex nummularia e gesso de jazida na fitorremediação de solo salino-sódico

LEAL, Isaac Gomes 01 August 2005 (has links)
Submitted by (lucia.rodrigues@ufrpe.br) on 2016-08-01T13:42:33Z No. of bitstreams: 1 Isaac Gomes Leal.pdf: 364436 bytes, checksum: df547cba6f7f5a24a0d9703117c5407d (MD5) / Made available in DSpace on 2016-08-01T13:42:33Z (GMT). No. of bitstreams: 1 Isaac Gomes Leal.pdf: 364436 bytes, checksum: df547cba6f7f5a24a0d9703117c5407d (MD5) Previous issue date: 2005-08-01 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The amelioration and use of saline-sodic soils through Atriplex nummularia cropping is economically attractive, especially because such species can be used as forrage crop or in landscape architeture projects. We evaluated the potential of Atriplex nummularia for phytoextraction of Na from a saline-sodic soil irrigated with saline water. Additionally, gypsum was tested for phytoremediation enhancement. The treatments were set up as follows: G0 = No gypsum and G1 = 50% of the regular recommended gypsum dose; Three water classes for irrigation: C1 = 175 μS cm-1; C2 = 500 μS cm-1; C3 = 1500 μS cm-1; and four sampling periods: T1 = 40; T2 = 70; T3 = 100 and T4 = 130 days after A. nummularia transplanting. The results showed that there was a 93%-increase in root dry matter as a result of gypsum application. The Na accumulation in shoots was significant increased at the third (90,1 g kg-1) and fourth (109,7 g kg-1) sampling. Such an effect was hastened owing to gypsum application. For the T3 treatment, Na content in soil decreased 30,75 and 25,78%, with and without gypsum addition. The percentage of exchangeable sodium was alsolower in the T3 treatment either with (19%) or without gypsum (11%). Our results indicate that A. Nummularia is a Na accumulator species. Gypsum was effective as a phytoextraction enhancer. A. nummularia irrigation aiming at Na phytoremediation can be implemented with saline waters ranging from 175 to 1500 uS cm-1. / Atriplex nummularia, apresenta-se como alternativa de uso e recuperação de solos salino-sódicos de baixo custo, podendo servir como suporte forrageiro e folhagem na floricultura e paisagismo. Com o objetivo de avaliar o potencial desta halófita na fitorremediação de solo salino-sódico sob irrigação com águas salinas e verificar o potencial do gesso como potencializador da fitoextração de sódio, foi conduzido um experimento em casa de vegetação, com os sguintes tratamentos: G0 = ausência de aplicação e G1 = 50% da dose recomendada pela necessidade de gesso; três classes de água para irrigação: C1 = 175 μS cm-1; C2 = 500 μS cm-1; C3 = 1500 μS cm-1; e quatro períodos de coleta: T1 = 40; T2 = 70; T3 = 100 e T4 = 130 dias após o transplantio da A. nummularia. O gesso influenciou significativamente a matéria seca de raiz, apresentando acréscimo de 93 %. O acúmulo de sódio nas folhas foi significativo a partir do terceiro tempo de coleta com valores de 90,1 e 109,7 g kg-1, rspectivamente para T3 e T4. Este efeito foi aumentado em 30 % com a aplicação de gesso. O teor de Na+ no solo foi menor em média 30,75 e 25,78 % a partir de tratamento T3 com e sem gesso respectivamente. A porcentagem de sódio trocávelfoi consideravelmente reduzida a partir do terceiro tempo de coleta, nos solos com e sem adição de gesso, apresentando reduções de 19 e 11 %, respectivamente. Com base nas condições estudadas, pode-se concluir que a Atriplex nummularia comportou-se como planta hiperacumuladora de sódio, possuindo potencial de uso na fitoextração deste elemento no solo. O uso do gesso de jazida promoveu o aumento da capacidade extrativa de sódio do solo pela planta, podendo ser usado como potencializador da fitoextração. A irrigação da A. numularia para uso de fitorremediação pode ser feita com águas salinas na faixa de 175 a 1500 μS cm-1.
30

Qualitative characteristics of selected Atriplex nummularia (Hatfield Select)

Snyman, Leendert D. 02 April 2007 (has links)
This study was conducted in two trials. The aim was firstly to identify the qualitative characteristics of Atriplex nummularia (Hatfield Select). Goats and sheep were used to identify three palatability groups of plants in the A. nummularia (Hatfield Select) paddock. These palatability groups were compared in terms of quality to one another. Secondly, qualitative and quantitative intakes of A. nummularia (Hatfield Select) by goats and sheep were determined. This was done in a grazing trial lasting five days. A comparison was conducted between goats and sheep as well as between the different days of the grazing period. During the first trial, goats and sheep were used to identify the most-, medium- and least-palatable A. nummularia (Hatfield Select) plants. The regrowth on these plants were harvested and used for laboratory analysis to identify the qualitative differences between these three groups. These samples were also used to determine and compare degradability between the three groups as well as between goats and sheep. Goats and sheep preferred A. nummularia (Hatfield Select) plants with a significantly (p ¡Ü 0.05) higher crude protein (CP), phosphorus (P) and magnesium (Mg) content. The most preferred plants also had higher neutral detergent fibre (NDF), Ca, K, Na, Cl- and Cu content than the least preferred plants, but these were not significant (p > 0.05). A. nummularia (Hatfield Select) provides enough CP for maintenance and production in both goats and sheep. All mineral requirements for maintenance in goats and sheep can be satisfied on A. nummularia (Hatfield Select), except that of Cu. For production (growth and lactation) only P is deficient and needs to be supplemented. A. nummularia (Hatfield Select) makes an ideal drought fodder crop to support the natural veld during the dry season. An overall higher DM, N and NDF rumen degradability of Atriplex was recorded with goats than with sheep. Goats exhibited a significantly (p ¡Ü 0.05) higher DM and N degradation and although a higher NDF degradation was also recorded, this was not significant. The rate of DM, N and NDF rumen degradation was also higher in goats than in sheep. This means that goats have a more favorable rumen environment for the digestion of A. nummularia (Hatfield Select). DM and N degradation were also significantly (p ¡Ü 0.05) higher in the most palatable group than the least palatable group. NDF degradability decreased with palatability. This means that the most palatable plants have a higher digestibility and quality than the least palatable plants. In the second experiment, rumen and oesophageal fistulated sheep and goats were allowed to graze A. nummularia (Hatfield Select) for five days. Qualitative and quantitative intakes were determined. The quality and quantity of ingested material were compared between goats and sheep as well as between the different grazing days. There was a significant decline in the quality and quantity of intake over the grazing period. Some parameters were significant, for example CP. The CP concentration declined from 18% to 3.91 % for goats and from 19.88% to 6.61% for sheep. The cell wall constituents (NDF) increased by about 10% from the start to the end of the grazing period. IVDOM decreased by 14% and intakes were almost halved from the start to the end of the grazing period. Other authors have also observed this decrease in quality and quantity of intake over time. The lower quality and quantity in intake was because of a decline in the availability of high quality edible material. At the end of the grazing period, there was very little edible material left which caused an extremely low quality and quantity of intake. Rumen NH3-N concentrations also declined as the dietary CP declined, but it was still present in high enough concentrations to sustain the rumen micro flora population. Rumen VFA decreased over the grazing period. The acetic acid to propionic acid ratio increased towards the end of the grazing period. This caused a decline in the efficiency of utilization of ME for maintenance as acetic acid has an efficiency in utilization of ME of 59% and propionic acid of 86% (McDonald et al., 1995). This means that energy will have to be supplemented to sustain maintenance. / Dissertation (MSc (Agric) Animal Science, Nutrition)--University of Pretoria, 2007. / Animal and Wildlife Sciences / unrestricted

Page generated in 0.0473 seconds