As propriedades físicas do solo são preponderantes para a qualidade e produtividade da cultura da batata. Assim, o objetivo do presente trabalho foi avaliar algumas propriedades físicas do solo e a produtividade e qualidade dos tubérculos de batata. O experimento foi instalado em áreas de produção de batata na Chapada Diamantina (BA), de abril a agosto de 2005. O solo foi preparado pelo sistema convencional e pelo sistema alternativo MAFES, ambos associados ou não com a aplicação de Microrganismos Eficazes (EM). Foram avaliadas: a densidade do solo, a estabilidade de agregados, a resistência do solo à penetração, a taxa de infiltração de água e a retenção de água no solo. Também foi avaliada a alteração dessas propriedades do solo em relação à área antes do preparo, que estava sob pastagem de Brachiaria brizantha. A massa de torrões e touceiras colhidas juntamente com os tubérculos, bem como os danos mecânicos verificados durante a colheita mecanizada e a porcentagem de tubérculos com danos causados por larva alfinete, sarna e podridões foram quantificados. A produtividade nos diferentes tratamentos foi avaliada dentro da classificação comercial. Em relação ao pasto, os preparos convencional e MAFES alteraram a maioria das propriedades físicas avaliadas. Na área preparada pelo sistema MAFES foi observado, em relação ao preparo convencional, menor resistência à penetração em profundidades de 20 a 45 cm e entre os camalhões. A taxa de infiltração de água foi semelhante entre as áreas preparadas pelos dois sistemas, porém no sistema convencional a infiltração é mais superficial ocorrendo de forma lateral ao longo do perfil. No sistema MAFES a infiltração ocorreu verticalmente no perfil do solo. Menor porcentagem de tubérculos com danos mecânicos foi obtida na área preparada pelo sistema MAFES, devido, principalmente, a menor massa de torrões e touceiras colhidas juntamente com os tubérculos nessa área. A aplicação de EM teve pouca influência nas propriedades físicas do solo, mas propiciou condições que favoreceram o ataque de larva alfinete e sarna aos tubérculos. Apesar da utilização de EM ter reduzido a produção de tubérculos na área preparada pelo sistema MAFES, a produtividade e qualidade dos tubérculos nessa área foi superior a da área preparada pelo sistema convencional. / The physical soil properties have a relevant role on the yield and quality of potato crop. Thus, the purpose of the present research was to evaluate the effects on some soil physical properties on productivity and quality of potato tubers. The trial was set up in a commercial potato production field located in the Chapada Diamantina, BA, from April to August, 2000. Two distinct soil preparation systems (conventional and MAFES system), either associated or not with application of EM, have been trialed. The following soil properties were evaluated: bulk density, aggregate stability, soil penetration resistance, soil water retention and water infiltration rate. In addition, were evaluated the changes of such soil properties in comparison with the area cultivated with the grass Brachiaria brizantha, prior soil preparation. Other evaluations were performed such as the clod mass and clump of roots harvested together with potato tubers, the level of damage to the tubers caused by mechanical harvesting, and the amount of tubers affected by potato tuber moth, rots, and common scab. The yields of the different treatments were evaluated and tubers graded according to commercial patterns. Compared to the grass, both conventional and MAFES soil preparation systems have changed the physical soil properties studied. MAFES system outperformed the conventional preparation giving lesser resistance to penetration at 20 to 45 cm deep and between hills. The water infiltration rate was similar for both soil preparation systems; however for the conventional system the infiltration pattern is superficial occurring laterally in the soil profile. Regarding MAFES systems, the infiltration occurred vertically. The area prepared MAFES system also gave a fewer percentage of tubers exhibiting mechanical damage, due to smaller clod mass and clump of roots harvested together with potato tubers. EM application did not benefit physical soil properties, however influenced a higher attack of potato tuber moth and common scab. Although the yield decrease in the area prepared with MAFES system when the EM was applied, in this area the productivity and tuber quality outperformed the conventional system.

Este ensaio clínico randomizado, cego e controlado com placebo teve como objetivo principal avaliar a eficácia do diamino fluoreto de prata (DFP) a 30% no tratamento não operatório de lesões de cárie em superfícies proximais de molares decíduos e compará-la a eficácia do infiltrante resinoso e a do controle do biofilme interproximal pelo uso do fio dental. Além disso, também avaliou a custo-eficácia e o desconforto dos tratamentos e a satisfação dos participantes quanto ao tratamento recebido. Para isso, foram selecionadas 141 crianças entre 3 e 10 anos de idade, que apresentavam pelo menos uma superfície proximal com lesão de cárie clinicamente em esmalte. A alocação dos participantes foi aleatória, de acordo com o tratamento: DFP a 30%, infiltrante resinoso de cárie e orientação para o uso diário do fio dental (controle). Todos os participantes receberam o tratamento ativo para os quais foram alocados e também o placebo dos tratamentos realizados nos outros grupos. Os custos dos materiais utilizados nos tratamentos foram registrados. Ao final da consulta de tratamento, foi aplicada aos participantes a Escala Facial de Wong-Baker para avaliação do desconforto. Os responsáveis pelos participantes, que concluíram o seguimento da pesquisa, responderam a um questionário de satisfação sobre o tratamento recebido. As crianças foram examinadas após 1 mês para avaliação de higiene bucal e também de presença de biofilme nas superfícies tratadas. Após 6, 12 e 24 meses, foram realizados exames visual e tátil para verificar a progressão das lesões tratadas, além de exame radiográfico aos 12 e 24 meses. Para avaliar a eficácia dos tratamentos, consideraram-se como desfechos: (I) qualquer progressão clínica da lesão tratada e (II) progressão para cavidade em dentina. A progressão radiográfica foi utilizada como um desfecho secundário e para comparar com o padrão clínico de progressão das lesões. Análises de regressão foram realizadas para verificar se os grupos de tratamento influenciaram os desfechos testados após 12 e 24 meses de seguimento (análise por protocolo - Poisson multinível e análise de sobrevida). Valores pontuais de custo-eficácia dos tratamentos foram calculados e, para comparar a custo-eficácia da implementação do uso do DFP em relação às outras opções testadas foi utilizada a razão de custo-eficácia incremental. Análises de regressão de Poisson foram utilizadas para verificar a associação entre o desconforto e variáveis explicativas. A satisfação dos participantes e seus responsáveis foi explorada descritivamente. Um total de 316 superfícies proximais foram incluídas, sendo a maioria classificada como escore 2 do ICDAS (Sistema Internacional de Detecção e Avaliação de Cárie) associadas à ausência de imagem radiográfica (46,8%). As perdas de seguimento foram de 15% e 24% aos 12 e 24 meses, respectivamente. Não houve associação entre o grupo de tratamento e a progressão das lesões aos 12 e 24 meses, tanta pela análise por protocolo como pela análise de sobrevida. A taxa de progressão clínica das lesões para cavidade em dentina foi de 2,5% aos 12 meses e de 5,6% aos 24 meses. As lesões que não apresentavam imagem radiográfica inicial não progrediram para o 1/3 médio de dentina ou mais. A condição clínica inicial das lesões foi associada à progressão das lesões em todas as análises. Já o risco de cárie foi associado à progressão das lesões aos 24 meses e também na análise de sobrevida. O tratamento com infiltrante resinoso apresentou o custo mais elevado, fazendo com que o tratamento com DFP apresentasse melhor relação custo-eficácia do que este primeiro. Os participantes tratados com o DFP e os que receberam orientação para o uso do fio dental relataram menor desconforto do que os tratados com o infiltrante resinoso. Os responsáveis se mostraram satisfeitos com o tratamento recebido, independentemente do grupo ao qual foram alocados. Conclui-se que o tratamento com DFP é tão eficaz quanto o infiltrante resinoso e a orientação para o uso do fio dental no controle das lesões iniciais em proximal de molares decíduos. No entanto, causa menor desconforto e apresenta custo-eficácia superior ao infiltrante resinoso, devendo ser preferível para superfícies proximais de molares decíduos, em situações nas quais o tratamento dessas lesões possa ser necessário, como por exemplo, pacientes com experiência de cárie. / This randomized, blinded and placebo-controlled clinical trial aimed to evaluate the efficacy of 30% silver diamine fluoride (SDF) as a non-operative treatment of the approximal surfaces of primary molars and to compare it with the efficacy of resin infiltration and the mechanical control of the interproximal biofilm by flossing. We also evaluated the cost-efficacy and the discomfort of the treatments as well as the parent\'s satisfaction regarding treatments. One hundred forty-one, 3-to-10-year-old, children were included. They must present at least one caries lesion clinically into enamel sited on an approximal surface of primary molar. Participants were randomly allocated to the following groups according to active treatment to be received: 30% SDF, caries resin infiltration, flossing orientation (control). All participants received the active treatment, in which they were allocated and they also received the placebo treatment corresponding to the other groups. Costs of materials used in the treatment were registered. In the end of treatment session, the Wong-Baker faces scale was applied to evaluate participants\' reported discomfort. Children were examined after 1 month to evaluation of the oral hygiene and the presence of the biofilm on the treated surfaces. After 6, 12 and 24 months, visual and tactile examinations were performed to verify the lesions progression. Radiography was taken at 12- and 24-month follow-ups. To evaluate the efficacy of non-operative treatments, two outcomes were considered: (I) any clinical progression and (II) progression to cavity into dentine. The radiographic progression was used as a secondary outcome and to evaluate with clinical standard of lesions progression. Regression analyses were used to verify if the treatment influenced on these outcomes after 12 and 24 months (per-protocol analyses - multilevel Poisson and survival analysis). Cost-efficacy ratios were calculated for the treatments. To compare the cost-efficacy of implementing the use of DFP versus other options tested, the incremental cost-efficacy ratio was used. Poisson regression analyses were used to verify the association between discomfort and explanatory variables. The parents\' satisfaction about the treatments were explored descriptively. A total of 316 approximal surfaces were included. The majority of them were classified as ICDAS (International Caries Detection and Assessment System) score 2 associated with absence of radiographic image. The dropout in the study was 15% and 24% at 12-month and 24-month follow-up, respectively. There was no association between treatment groups and lesions progression at 12 and 24 months, both for the per-protocol analysis and by survival analysis. The rate of clinical lesions progression to cavity into dentine was 2.5% at 12 months and 5.6% at 24 months. Lesions without initial radiographic image did not progress into the middle of the dentine or more. Baseline clinical condition of caries lesions was associated with lesions progression in all analyses. The caries risk was also associated to caries progression in 24-month analyses and in the survival analyses. The treatment with resin infiltration was costlier. Consequently, the treatment with SDF was more cost-effective than resin infiltration. The participants allocated to SDF and control groups reported less discomfort than those who was allocated to the resin infitrant group. The parents were satisfied with the treatment received during the study, independently of the group to which their children had been allocated. It is possible to conclude that the SDF is as efficacious as the resin infiltration and flossing orientation to control initial lesions in the approximal surfaces of primary molars. However, SDF causes less discomfort and presents superior cost-efficacy relationship than resin infiltration and could be preferable to treat approximal caries in primary molars in those situations in which the treatment could be necessary, for example, depending on patients\' caries experience.

Made available in DSpace on 2017-07-10T15:14:38Z (GMT). No. of bitstreams: 1 Cristiano.pdf: 1521067 bytes, checksum: 8be179f3b8b51910029f0a61831b2fc6 (MD5) Previous issue date: 2016-04-07 / Urbanization and the disorderly occupation of cities have created many environmental problems, ranging from floods to climate change in large urban centers. Among the causes of these occurrences is mainly soil sealing in cities, that occurs by interference and man's need to use more space. The more waterproofed the surface of urban areas, higher runoff, and this, in turn, due to the adopted public politics and the lack of planning, are transferred to adjacent watersheds, causing, these problems such as floods and silting of rivers. The impermeabilized surfaces end up affording a smaller charge of watersheds, transferring to other river basins the amount of water that it should be restored in the region, that way impair the recovery of the basins where the percolations occur. This study is a comparison between two existing technologies in commercially known market as "paver" and "draining floor", and point which of these can help in the recovery of watersheds and, consequently, reduce the problems caused by surface runoff in urban areas. To reach the result precipitations were simulated using a sprinkler infiltrometer in intensities corresponding to 45mm.h-1, 60mm.h-1 and 90mm.h-1, and occurred in lysimeters where the coverages match the public walks characteristics using the technologies to be analyzed as ground cover. This experiment showed that the permeable concrete parts (draining floor) and concrete parts gaskets extended (paver) has percolation rate likened to grass cover and thus can be used as technologies for water infiltration into the soil aiding in the recovery of watersheds in urban areas / A urbanização e a ocupação desordenada das cidades criaram diversos problemas ambientais, que vão desde enchentes até alterações climáticas nos grandes centros urbanos. Entre as causas destas ocorrências está, principalmente, a impermeabilização dos solos nas cidades, que ocorre pela interferência e necessidade do homem em utilizar mais espaço. Quanto mais impermeabilizada a superfície das regiões urbanas, maior o escoamento superficial, e este, por sua vez, devido às políticas públicas adotadas e à falta de planejamento, são transferidos para bacias adjacentes, trazendo problemas a estas, como enchentes e assoreamentos dos rios. As superfícies impermeabilizadas acabam proporcionando uma menor recarga das bacias hidrográficas, transferindo para outras bacias a quantidade de água que deveria ser reposta naquela região, desta forma prejudicam a recuperação das bacias onde ocorrem as percolações. O presente estudo faz um comparativo entre duas tecnologias existentes no mercado comercialmente conhecidos como paver e o piso drenante , e apontará qual destas pode auxiliar na recuperação das bacias hidrográficas e, consequentemente, reduzir os problemas causados pelo escoamento superficial nas regiões urbanas. Para chegar ao resultado foram simuladas precipitações utilizando um infiltrômetro de aspersão em intensidades correspondentes à 45 mm.h-1, 60 mm.h-1 e 90 mm.h-1, e ocorreram em lisímetros onde as coberturas correspondem as características de passeios públicos utilizando as tecnologias a serem analisadas como cobertura de solo. Este experimento apontou que as peças de concreto permeável (piso drenante) e as peças de concreto com juntas alargadas (paver) têm taxa de percolação assemelhada a cobertura de grama e desta forma podem ser utilizadas como tecnologias para infiltração de água no solo auxiliando na recuperação das bacias hidrográficas das zonas urbanas.

<p>Istraživanja predstavljena u disertaciji imala su za cilj formiranje<br />regresionog modela procesa vakuumske infiltracije u postupku vezivne<br />3D štampe, radi uspostavljanja analitičke zavisnosti između ključnih<br />tehnoloških parametara infiltracije i mehaničke čvrstoće<br />infiltriranih epruveta. Dizajn eksperimenta i optimizaciju<br />parametara su izvršeni korišćenjem novog postupka dizajna<br />eksperimenta, Definitive Screening Design. U poređenju sa literaturno<br />dostupnim rezultatima zatezne čvrstoće, dobijenim primenom<br />komercijalnih prahova, vezivnih sredstava i epoksidnih infiltranata,<br />optimizovanim parametrima vakuum infiltracije zatezna čvrstoća<br />epruveta je poboljšana za 23%.</p> / <p>The research presented in this thesis was aimed at forming a regression<br />model of the vacuum-assisted infiltration process in binder printing<br />technology (3DP). The goal was to establish analytical relationship between<br />key infiltration technological parameters and tensile strength of infiltrated<br />parts. The design of experiment and optimization of the infiltration process<br />was performed using a novel Definitive Screening Design method. Compared<br />to the literature results which pertain to tensile strength obtained using<br />commercial powders, binders, and epoxy infiltrates, the optimized model of<br />vacuum-assisted infiltration yielded an increase of 23% in tensile strength.</p>

Le Tea Party entre en scène en février 2009 aux États-Unis. C’est notamment la tirade d’un journaliste qui s’insurge contre les plans de sauvetage de l’économie votés par le Président Barack Obama, en direct sur la chaîne CNBC le 19 février, et invite à organiser une « Tea Party » dans le port de Chicago, qui déclenche ce phénomène sans précédent. S’ensuivent de nombreux rassemblements protestataires de masse à travers le pays, puis la création de dizaines, puis de centaines de groupes Tea Party locaux. La rapidité et l’ampleur de ce mouvement surprennent les spécialistes. D’autant que dès 2010, le Tea Party affirme des objectifs politiques et une volonté d’institutionnalisation, se révélant une menace pour l’establishment républicain. Mais en 2012, la réélection du Président Obama peut être lue comme une défaite colossale pour le mouvement, et des chroniques de mort annoncée sont publiées par la presse libérale (au sens américain). Des résultats peu spectaculaires aux élections de mi-mandat en 2014 semblent confirmer ce pronostic, surtout que le Parti républicain réussit à tenir le mouvement en respect jusqu’aux primaires pour l’investiture présidentielle en 2015. C’est alors qu’on assiste à un retournement de situation ; la radicalisation du Grand Old Party est nette, visible entre autres dans la plate-forme très conservatrice des candidats républicains. En novembre 2016, l’élection de l’outsider Donald Trump à la présidence, conjonction de nombreux facteurs électoraux, est également le résultat d’efforts organisationnels de la Droite auxquels le Tea Party a largement contribué. Pour appréhender ce mouvement, il faut comprendre qu’il combine des forces top-down et bottom-up. Certes, le Tea Party bénéficie depuis son émergence de ressources inestimables de la part de groupes de pression et de think tanks comme FreedomWorks, American Majority, Americans for Prosperity ou Heritage Foundation, ainsi que des médias conservateurs. De nature organisationnelle ou rhétorique, ces ressources sont fondamentales car elles permettent au mouvement de s’organiser et de mener ses actions militantes. Il n’en reste pas moins qu’à la base se trouvent des acteurs bénévoles, qui consacrent leur temps et leur énergie au Tea Party, et revendiquent leur caractère grassroots. Des organisations nationales comme Tea Party Patriots s’imposent pour fédérer les groupes qui leur sont affiliés, cependant certains groupes locaux cherchent à protéger leur indépendance. Autour des groupes Tea Party gravitent des organisations libertariennes et conservatrices, l’ensemble formant une nébuleuse complexe, qui fonctionne par réseaux à différents niveaux et selon diverses configurations. L’objet de cette étude de terrain est donc d’apporter un éclairage de l’intérieur du mouvement Tea Party, par l’observation en immersion de groupes locaux situés dans les régions de Philadelphie en Pennsylvanie, et de Boston dans le Massachusetts. Il s’agit d’abord de comprendre les motivations et l’idéologie des militants, principalement d’orientation conservatrice, libertarienne et populiste. Ce sont les notions de souveraineté individuelle, d’anti-fédéralisme, et de respect de la Constitution qui dictent toute lecture des Tea Partiers. Ensuite, l’analyse des modes opératoires des groupes permet de clarifier le fonctionnement de l’ensemble. Le Tea Party se démarque en tant que mouvement de droite recourant à des stratégies organisationnelles jusqu’ici plutôt réservées aux mouvements progressistes - la façon dont il applique les principes de l’organisation communautaire est l’une de ses forces indéniables, en particulier à l’ère des nouvelles technologies, et des réseaux sociaux. Son utilisation de ressources Web et d’outils concrets pour l’action militante est remarquable. Enfin, il est essentiel de saisir que le Tea Party veut s’implanter dans le tissu décisionnel local. Pour y parvenir, l’une de ses tactiques consiste à infiltrer progressivement le Parti républicain / The Tea Party enters the scene in February 2009 in the United States. On February 19, a CNBC journalist protests on-air against the economic bailout plans voted by President Barack Obama, and invites viewers to organize a « Tea Party » in the Chicago harbor. This contributes to trigger an unprecedented phenomenon, as numerous mass protest rallies soon organize throughout the country, followed by the creation of dozens, then hundreds of local Tea Party groups. Experts are astonished at the swiftness and magnitude of the movement. All the more so in 2010, when the Tea Party starts claiming political objectives and shows intent of institutionalizing, proving a threat to the Republican Establishment. However, President Obama is reelected in 2012 and this is interpreted as a devastating loss for the movement, for which obituaries are published in several liberal media. Lackluster results in the 2014 mid-term elections seem to confirm this forecast, especially since the Republican Party succeeds at keeping the movement at bay until the primaries for the presidential candidate nomination in 2015. But then there is a reversal; the Grand Old Party clearly radicalizes, as the extremely conservative Republican platform notably shows. And the election of outsider Donald Trump to the presidency in November 2016, a conjunction of numerous electoral factors, is also the result of organizational efforts on the right side of the political spectrum, to which the Tea Party largely contributed. To better apprehend this movement, it is necessary to understand that it combines top-down and bottom-up forces. From its appearance, the Tea Party has indisputably benefitted from colossal resources from interest groups and think tanks such as FreedomWorks, American Majority, Americans for Prosperity or The Heritage Foundation, but also from conservative media. Either organizational or rhetorical, these resources are primeval for the movement’s organization and activism. Nevertheless, there are voluntary activists working at the basis of the movement, who devote their time and energy to the Tea Party, and claim its grassroots nature. National organizations such as Tea Party Patriots try to establish themselves as federations for the groups affiliated to them, while some local groups seek to remain independent. Libertarian and conservative organizations gravitate around Tea Party groups, the whole forming a complex cluster that operates at different levels and following diverse configurations. Thus the object of this field study is to shed light on the Tea Party movement from the inside, thanks to the observation of local groups from an embedded position. These groups are located in the Philadelphia and Boston areas, respectively in Pennsylvania and Massachusetts. First, it is necessary to understand activists’ motivations and ideologies, which are mainly conservative, libertarian and populist; and that Tea Partiers interpret everything though the lens of individual sovereignty, anti-Federalism, and respect of the Constitution. Then, analyzing the modi operandi of the groups allows to illuminate how the whole system works. The Tea Party distinguishes itself as a right-wing movement that recurs to organizational strategies that were predominantly used by progressive movements until recently – the way the movement applies the principles of community organizing is undeniably one of its strengths, particularly considering the new media revolution, and social networks. Its use of Web resources and concrete tools to encourage activism is impressive. Lastly, it is indispensable to grasp that the Tea Party aims for local decision-making positions. To this end, one of its tactics consists in progressively infiltrating the Republican Party

: The topic of artificial recharge technology for water supply into the underground, its direct use and application in the field is becoming a more frequent foreign question, but also in the Czech Republic. This is due to the negative trend in groundwater levels over the past 10 years, caused by drought and temperature regression trends. The theoretical part of this thesis presents the knowledge of the use of artificial groundwater recharge, even with specific cases in the world or in the Czech Republic. This work is especially focused on a very specific case of the construction that represent underground dam in the village of Meziboří in the environment of the Czech massif "hard rocks". Specifically, its efficiency and impact on natural groundwater runoff. For this purpose, a numerical model was developed in the program Groundwater Vistas (extension for MODFLOW). From the results we can observe the influence of natural groundwater regime in both static and dynamic model. After simulating the dam in a steady- state regime of unaffected conditions, the groundwater level in the model before the dam increased significantly above ground level. The possible pumping without drying the collector then represents values 5,4 - 5,8 m3 /day (0,063 - 0,067 l/s) from the well just before the dam. The drain...

During the period of October 1974 to August 1976, a study was conducted to measure the effects of surface soil removal on plant production, plant transpiration rates, nitrate nitrogen mineralization rates, and selected hydrologic parameters (infiltration rates, potential sediment production, and chemical quality of runoff water). The treatments were incremental 7.6 centimeter soil layers to a depth of 30.5 centimeters. Plant production and transpiration ratios (or water use efficiencies) were measured in greenhouse studies using Agrogyron desertorum grown in the incremental 7.6 centimeter soil layers from five study sites throughout the state of Utah, (Blanding, Brush Creek, Milford, Huntington, and Dove Creek). Significant decreases in plant production and increases in transpiration ratios were measured for all sites at incremental depths beyond 7.6 centimeters. These changes in plant production and transpiration ratios were found to be linearly related to the nitrate nitrogen content of the soils as determined at the time the soils were collected for use in the greenhouse. Nitrogen mineralization rates for a 6 week period were measured under field conditions at Milford and Blanding for each of the 7.6 centimeter incremental soil layers. Nitrate nitrogen mineralization was linearly correlated to the organic carbon content of the soil. Decreased mineralization rates as measured in the field at both study sites were reflected in significant increases in plant water requirements and also decreases in production as measured in greenhouse studies. Hydrologic parameters were measured at each 7.6 centimeter incremental soil depth using a Rocky Mountain infiltrometer. With one exception, significant differences in infiltration capacities among treatment depths did not occur during either 1975 or 1976 at either the Blanding or Milford site. At the Blanding site a significant decrease in the infiltration capacity occurred beyond the 22.9 centimeter depth due to a hardpan development. A significant change in infiltration capacities was noted between the 1975 and 1976 field seasons as pooled over both treatment depths and study sites. There were no significant differences in potential sediment production between sites or among treatment depths within a site. In terms of runoff water quality, a significant change in phosphorus was observed only at the Blanding site between the 1975 and 1976 field seasons. Significant differences in potassium concentrations were found to exist between sites and among soil depths.

Aggregate breakdown is an important process controlling the availability of fine soil material necessary for structural sealing of soil surfaces under rainfall. It may be caused by slaking resulting from rapid soil wetting and by physical dispersion resulting from direct and indirect energetic raindrop impacts. Relationships have been proposed by others predicting steady infiltration rate and saturated hydraulic conductivity from final aggregate size following high energy rainfall on initially dry, uncovered soil surfaces. Under these extreme conditions, both rapid wetting and energetic raindrop impact result in maximum aggregate breakdown and surface sealing. Knowledge of the relative importance of these two agents under less severe conditions and knowledge of how increased aggregate stability due to conservative soil management may ameliorate them should improve prediction and management of aggregate breakdown and surface sealing. ¶ This study has isolated and quantified effects of rapid soil wetting and energetic raindrop impact on aggregate breakdown and surface sealing. Simulated rainfall was applied to re-packed soils from differing tillage treatments on light textured soils from near Cowra and Condobolin in New South Wales, Australia. Aggregate breakdown was assessed using aggregate size distribution, determined by wet sieving and summarised by a range of statistics. The degree of breakdown was assessed after 66 mm of simulated rainfall whilst the rate of change in aggregate size distribution was assessed by sampling after 5, 10, 15, 30 and 60 mm. The degree of surface sealing was assessed using final surface hydraulic conductivity after 66 mm rainfall calculated from inferred infiltration and measured sub-seal soil water potential. The rate of surface sealing was assessed prior to ponding using cumulative rainfall volume at ponding and throughout the post-ponding phase by decline in surface hydraulic conductivity as a function of cumulative rainfall kinetic energy. Two levels of raindrop kinetic energy flux and three wetting treatments were used to isolate effects of these agents of aggregate breakdown and surface sealing. ¶ Significant surface aggregate breakdown was observed when either rapid soil wetting or highly energetic raindrop impact were allowed to occur. The majority of the data suggest a negative interaction between the two agents. When soil was initially dry rapid soil wetting was the dominant agent causing rapid aggregate breakdown, generally within the first 5 mm of rainfall. When rapid soil wetting was prevented by tension pre-wetting, energetic raindrop impact was the dominant agent and was able to cause aggregate breakdown of an almost equivalent degree. This breakdown occurred over a period lasting for up to 30 mm of rainfall. In contrast, the rate and degree of surface sealing were influenced primarily by raindrop kinetic energy with highly energetic impact leading to significant surface sealing, irrespective of soil wetting. For the soils studied, it was concluded that structural sealing of surface soil, could be significantly reduced by protecting the soil surface from energetic raindrop impact but that prevention of surface aggregate breakdown required amelioration of both processes. ¶ In addition to the negative interaction referred to above, a positive interaction was observed whereby energetic raindrop impact occurring concurrently with rapid soil wetting caused a greater degree of aggregate breakdown and a greater degree of surface sealing than energetic raindrop impact occurring subsequent to rapid soil wetting. The effect on surface sealing may be explained by the effect of lower sub-seal water potential that necessarily results from initially dry soil condition required for concurrent rapid wetting. However, the effect on aggregate breakdown remains unexplained. ¶ Notwithstanding the above, permeability was reduced under high kinetic energy rainfall even when soil wetting was reduced to very slow rates by tension pre-wetting. Likewise, surface sealing did occur under low kinetic energy rainfall for the least stable soil following rapid soil wetting. It was concluded that threshold soil wetting rates and threshold rainfall energy levels, proposed by others, are either not applicable to these soils or are negligible. ¶ The rate and degree of aggregate breakdown was also dependent on the soil with the Cowra soil being more stable than the Condobolin soil. Greater aggregate stability brought about by conservative tillage treatments at both soil locations retarded and reduced surface sealing. Unvalidated simulation modelling was used to illustrate possible effects for the soil water balance. In contrast to the conclusions of Loch (1994b), that were based on soils throughout eastern Queensland, the soil water balance simulations predicted that the residual benefits in ameliorating surface sealing resulting from improved aggregate stability could significantly reduce point runoff under the lower intensity winter rainfalls experienced in southern New South Wales. ¶ Limited testing with Condobolin soil following tension pre-wetting showed that rainfall intensity, varying over the range from 16.5 to 66 mm h-1, had little effect on the decline in surface hydraulic conductivity as a function of cumulative rainfall kinetic energy. This contrasts with greater seal permeability under higher rainfall intensities observed by Romkens et al. (1985) and others. It is proposed that an alternative explanation exists for the observations of Romkens et al. based on reduction in seal permeability due to lower sub-seal water potential under lower intensity rainfall. ¶ Post-ponding reduction in K[subscript sat] under high kinetic energy rainfall exhibited exponential decline as a function of cumulative raindrop kinetic energy as proposed by Moore (1981b). However, inferred rates of decline prior to ponding were more rapid than measured post-ponding rates suggesting that infiltration models using only a single exponential rate of surface K[subscript sat] decline based on post-ponding measurements may be in error. Potential for error is greatest at early times for loose soil that is highly susceptible to sealing. ¶ Pre-ponding decline in surface aggregation was also relatively more rapid than post-ponding decline. This discrepancy was evident irrespective of soil pre-wetting. From this it was concluded that the more rapid initial aggregate breakdown and surface sealing was due, at least in part, to processes other than aggregate slaking due to rapid soil wetting. An explanation has been proposed as follows. Raindrops initially fall on aggregates that have not been subjected to rainfall and therefore each drop has the capacity to cause greater aggregate breakdown than subsequent raindrops that fall on aggregates or soil fragments that have been strong enough to survive preceding rainfall impacts. Such a mechanism could provide an alternative explanation of the findings of Baumhardt et al. (1991) who found that less cumulative raindrop kinetic energy was necessary to achieve a given reduction in surface conductance when the cumulative energy was supplied through lower energy drops. ¶ Relationships predicting rates of surface sealing using aggregate breakdown under rainfall and aggregate stability were evaluated. Post-ponding infiltration rate and surface K[subscript sat] were related to aggregate size by exponential functions. The proportion of surface aggregates less than 0.125 mm in diameter provided slightly more consistent relationships. Parameters of fitted relationships differed among wetting pre-treatments suggesting that the influence of sub-seal water potential on surface K[subscript sat] must be considered whenever such relationships are developed or applied. Aggregate stability determined by wet sieving was related to rainfall volume required for ponding, final K[subscript sat] and final aggregate size but only for initially dry soil suggesting that such relationships may be unique to the rainfall, soils and flow conditions used to develop them. ¶ This study has established the relative importance of rapid soil wetting and energetic raindrop impact in both aggregate breakdown and surface sealing over a range of antecedent soil water and rainfall conditions. It has quantified the effectiveness of culturally induced aggregate stability in ameliorating effects of these two important agents and illustrated the potentially significant consequences for the soil water balance. It has quantified temporal patterns of surface sealing and aggregate breakdown and proposed an alternative mechanism explaining more rapid aggregate breakdown during the initial stages of rainfall. It has identified possible explanations for effects of rainfall intensity on surface sealing observed in other studies. It has also partially evaluated a mechanism proposed to explain important effects of subseal water potential on seal permeability found in this and other studies. These significant findings have been used with the findings of other studies to amend the conceptual model proposed by Le Bissonnias (1990). The amended model gives a more complete description of the relationships between parameters and processes determining aggregate breakdown and structural surface sealing under rainfall.

Cette étude a pour objectifs la compréhension et la modélisation de certains effets importants du semis direct avec paillis de résidus (SDP) sur les bilans hydrique, thermique et azoté d'une culture de maïs pluvial. Elle a été menée dans le contexte d'un climat tropical semi-aride au Mexique. D'un point de vue méthodologique, le travail a consisté tout d'abord à identifier les phénomènes physiques et biologiques principaux qu'implique l'itinéraire technique SDP. En s'appuyant sur les résultats de la littérature et sur les acquis au niveau du terrain d'étude, nous avons retenu comme prédominants les effets du SDP sur i) l'évaporation et la température du sol, ii) la structure de surface du sol et l'infiltration, iii) le ruissellement, et iv) le cycle de l'azote et l'activité biologique des sols.<br />Ces effets identifiés, une lourde campagne de collecte de données de terrain a été réalisée de mai à octobre 1998, sur le site expérimental de la Tinaja (état de Jalisco, Mexique). Des mesures complémentaires ont été faites en juin et juillet 1999 sur le même site. Certaines mesures difficilement réalisables sur le terrain ont été effectuées en laboratoire, et sont venues renforcer les données du terrain. A l'issu de ce travail expérimental important, nous disposons d'une base de données relativement riche sur l'ensemble des phénomènes étudiés.<br />L'étude théorique des effets du SDP s'est déroulée en deux phases. La première s'appuie sur une stratégie d'atomisation de la problématique en volets élémentaires spécifiques, traitant les effets du SDP sur i), ii) et iii), en milieu contrôlé. Le premier volet vise à étudier et modéliser les flux d'eau et de chaleur dans le système sol-paillis-atmosphère (transferts turbulents et radiatifs au sein du paillis). Il permet de comprendre et de quantifier l'effet d'un paillis de résidus sur l'évaporation d'un sol et son amplitude thermique, en fonction du taux de couverture. Le deuxième volet consiste à caractériser les effets cumulatifs du SDP sur les propriétés hydrodynamiques d'un sol et donc sa capacité à l'infiltration. Le troisième volet est dédié à l'étude et la modélisation du ruissellement sur sol paillé éventuellement planté, en tenant compte de l'interception de l'eau de pluie, de la rétention de surface, de l'infiltration, de la canalisation du ruissellement et de son écoulement. La deuxième phase relève de la reconstruction par intégration et consiste en un volet unique. Dans ce volet les résultats des trois volets spécifiques précédents sont synthétisés et intégrés dans un modèle numérique de fonctionnement global. Ce dernier prend en compte à la fois les dynamiques de l'eau, de la chaleur et de l'azote. Il reproduit simultanément et de façon couplée tous les effets majeurs du SDP sur le système sol-paillis-plante-atmosphère.

La détermination de certains paramètres hydrodynamiques dans les modèles d'écoulement en zone non-saturée (et plus généralement dans certains modèles géophysiques) requiert l'utilisation d'un modèle et de données d'observations. Le but de ce travail est de proposer une méthode d'assimilation variationnelle de données permettant de reconstituer ces paramètres en tenant compte des observations et le modèle. La méthode proposée est fondée sur les techniques de contrôle optimal. Le travail mené dans cette étude porte sur l'identification de paramètres sur le modèle de Richards monodimensionnel ainsi que sa mise en oeuvre numérique. Au préalable, une investigation de la physique liée à notre problématique est explorée. Les données à assimiler sont les mesures d'infiltration cumulée et le vecteur de contrôle choisi est constitué de la condition initiale, des conditions aux limites et des paramètres hydrodynamiques. C'est ainsi que suivant certaines distributions des observations (infiltration cumulée observée), le paramètre de contrôle est reconstitué. Cette phase est suivie par une étude a posteriori basée sur les études au second ordre qui permettent d'estimer l'erreur de l'identification, l'influence de la configuration temporelle des observations sur la qualité de l'identification ainsi qu'une bonne compréhension du processus de minimisation. La dérivation automatique à l'aide du logiciel de différentiation automatique ODYSSEE est utilisée pour déduire les informations du premier et du second ordre. Enfin, en se servant des études au second ordre réalisées, nous appliquons l'algorithme de Newton au système d'optimalité.