Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2001. / Härtill 5 uppsatser.

Made available in DSpace on 2014-06-11T19:23:24Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-04-28Bitstream added on 2014-06-13T18:50:29Z : No. of bitstreams: 1 almeida_cx_me_jabo.pdf: 1204259 bytes, checksum: 236a0af5f42cb1b639ed5de10c3cc693 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A estimativa da curva de resistência do solo à penetração (CRP), a partir de variáveis de fácil obtenção, como o conteúdo de água (Ug), representa uma medida muito útil não só para a quantificação do estado de compactação, mas também para facilitar a interpretação da resistência do solo à penetração (RP), obtida em diferentes condições de campo. O objetivo foi estimar a CRP em solos de diferentes granulometrias e densidades, a partir de dados obtidos com o penetrômetro de impacto. O experimento foi realizado em laboratório, na Faculdade de Ciências Agrárias e Veterinárias (UNESP), Jaboticabal, SP. Foram utilizadas quatro classes de solos: Neossolo Quartzarênico, Argissolo Vermelho-Amarelo, Latossolo Vermelho Distrófico e Latossolo Vermelho Acriférrico, os quais foram amostrados na camada de 0-0,20 m. Colunas de PVC foram preenchidas de forma a se obter diferentes condições de densidade: solo não compactado e compactado. O Ug, inicialmente elevado até o ponto de saturação, foi monitorado diariamente através de um medidor eletrônico composto pelo Profile Probe PR2 acoplado ao Moisture Meter HH2. A RP foi mensurada através de um penetrômetro de impacto adaptado para vaso. Os pares de dados entre a RP e o Ug foram ajustados e as CRP submetidas ao teste de significância. A relação entre a RP e o Ug foi descrita pelo modelo exponencial decrescente, representado pela seguinte equação: RP = a+be Ug/c em que: RP representa a resistência do solo à penetração (MPa); Ug o conteúdo gravimétrico de água (kg kg-1) e a, b e c são os parâmetros da equação. Foram obtidos coeficientes de determinação que variaram de 0,57 a 0,96. / The estimate of soil resistance to penetration curve (RPC) from easy attainment variables, like the water content (Wc), represents a very useful measure not only in the evaluation of soil compaction, but also to simplify the interpretation of the soil resistance to penetration (SR) obtained in different field conditions. The objective was to estimate the RPC in soils of different textures and bulk densities, from data obtained with the impact penetrometer. The experiment was carried out in Faculdade de Ciências Agrárias e Veterinárias (UNESP), Jaboticabal, SP, and four classes of soil were used: Entissol, Alfissol, Oxisol medium texture and clayey Oxisol, which were collected at 0-0.20 m soil depth. The PVC columns filled in manner to obtain a condition of non compacted and compacted soil. The Wc, initially elevated to the saturation point, was daily monitored through an electronic measurer composed by Profile Probe (PR2) connected to a Moisture Meter HH2. The SR was measured by an impact penetrometer adapted to the vase. The pairs of data between SR and Wc were adjusted and the RPC submitted to the significance test. The equation that best described the relationship between the SR and Wc was the exponentially decreasing, as follows: SR = a+be Wc/c where SR is the soil resistance to penetration (MPa), Wc soil water content (kg kg-1) and a, b and c are the parameters of the equation. There was a significant relation between soil resistance to penetration and water content and the equations fit the data with coefficients of determination ranging from 0.57 to 0.96.

Orientador: José Frederico Centurion / Banca: Elias Nascentes Borges / Banca: Itamar Andrioli / Resumo: A estimativa da curva de resistência do solo à penetração (CRP), a partir de variáveis de fácil obtenção, como o conteúdo de água (Ug), representa uma medida muito útil não só para a quantificação do estado de compactação, mas também para facilitar a interpretação da resistência do solo à penetração (RP), obtida em diferentes condições de campo. O objetivo foi estimar a CRP em solos de diferentes granulometrias e densidades, a partir de dados obtidos com o penetrômetro de impacto. O experimento foi realizado em laboratório, na Faculdade de Ciências Agrárias e Veterinárias (UNESP), Jaboticabal, SP. Foram utilizadas quatro classes de solos: Neossolo Quartzarênico, Argissolo Vermelho-Amarelo, Latossolo Vermelho Distrófico e Latossolo Vermelho Acriférrico, os quais foram amostrados na camada de 0-0,20 m. Colunas de PVC foram preenchidas de forma a se obter diferentes condições de densidade: solo não compactado e compactado. O Ug, inicialmente elevado até o ponto de saturação, foi monitorado diariamente através de um medidor eletrônico composto pelo Profile Probe PR2 acoplado ao Moisture Meter HH2. A RP foi mensurada através de um penetrômetro de impacto adaptado para vaso. Os pares de dados entre a RP e o Ug foram ajustados e as CRP submetidas ao teste de significância. A relação entre a RP e o Ug foi descrita pelo modelo exponencial decrescente, representado pela seguinte equação: RP = a+be Ug/c em que: RP representa a resistência do solo à penetração (MPa); Ug o conteúdo gravimétrico de água (kg kg-1) e a, b e c são os parâmetros da equação. Foram obtidos coeficientes de determinação que variaram de 0,57 a 0,96. / Abstract: The estimate of soil resistance to penetration curve (RPC) from easy attainment variables, like the water content (Wc), represents a very useful measure not only in the evaluation of soil compaction, but also to simplify the interpretation of the soil resistance to penetration (SR) obtained in different field conditions. The objective was to estimate the RPC in soils of different textures and bulk densities, from data obtained with the impact penetrometer. The experiment was carried out in Faculdade de Ciências Agrárias e Veterinárias (UNESP), Jaboticabal, SP, and four classes of soil were used: Entissol, Alfissol, Oxisol medium texture and clayey Oxisol, which were collected at 0-0.20 m soil depth. The PVC columns filled in manner to obtain a condition of non compacted and compacted soil. The Wc, initially elevated to the saturation point, was daily monitored through an electronic measurer composed by Profile Probe (PR2) connected to a Moisture Meter HH2. The SR was measured by an impact penetrometer adapted to the vase. The pairs of data between SR and Wc were adjusted and the RPC submitted to the significance test. The equation that best described the relationship between the SR and Wc was the exponentially decreasing, as follows: SR = a+be Wc/c where SR is the soil resistance to penetration (MPa), Wc soil water content (kg kg-1) and a, b and c are the parameters of the equation. There was a significant relation between soil resistance to penetration and water content and the equations fit the data with coefficients of determination ranging from 0.57 to 0.96. / Mestre

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The knowledge of soil moisture is quite important because it indicates soil hydric conditions and it can help on saving water and electric energy, given that monitoring of soil moisture allows controlled and timely applications of water pointing out how much and when to irrigate, according to the crop water requirements. Therefore, soil moisture should be determined before the irrigation and will serve as a parameter for the amount of water to be applied by the system. There are any methods used for determination of soil water content, in this way, the present study aimed to compare the results of soil moisture obtained by different methods for expeditious determination of the water content of the soil in different textural classes. The study was conducted in the Laboratório de Hidráulica Agrícola da Universidade Federal de Santa Maria . Four methods were tested (standard method, M0; electric oven method, M1, microwave oven method, M2; weighing method, M3) with three soil samples (S1, S2, S3) and three repetitions for each. The linear regression was made between the standard method and alternative methods, for obtaining the correlation coefficient (r), the linear coefficient and the slope, the Wilmott concordance index (Iw) and Performance Index (Id). From the results obtained can be stated that the electric oven method and the microwave oven method have excellent performance when compared to the standard method. The method of weighing presented a performance good and very good. In addition, it was concluded that the 20 minutes period for the electric oven method was efficient signifying a time reduction for the moisture content determination. For the microwave oven method the 5 minute drying period was sufficient and did not differ statistically from the standard method. The method of weighing was also reliable in determining soil moisture. Therefore, it is possible to use alternative methods to determine the soil moisture. / O conhecimento da umidade do solo é de fundamental importância, pois indica em que condições hídricas encontra-se o mesmo, podendo auxiliar na redução dos gastos com água e energia elétrica, haja vista que o monitoramento da umidade do solo possibilita aplicações controladas e pontuais de água, respondendo o quanto e quando irrigar em função das necessidades hídricas das culturas. Assim sendo, para a realização da irrigação, a umidade do solo deve ser determinada anteriormente e servirá de parâmetro para a quantidade de água a ser aplicada pelo sistema. Inúmeros são os métodos utilizados para a determinação do conteúdo de água no solo, dessa maneira, o presente trabalho objetivou comparar os resultados de umidade do solo obtidos pelos diferentes métodos expeditos para determinação do conteúdo de água no solo em diferentes classes texturais. O estudo foi desenvolvido no Laboratório de Hidráulica Agrícola da Universidade Federal de Santa Maria. Foram testados quatro métodos (método padrão de estufa, M0; método do forno elétrico, M1, método do forno de micro-ondas, M2; método das pesagens, M3), com três amostras de solo (S1, S2, S3) e três repetições para cada. Foi feita a regressão linear entre os métodos alternativos e o método padrão de estufa, com a finalidade de se obter o coeficiente de correlação (r), o coeficiente linear e o coeficiente angular, o índice de concordância de Wilmott (Iw) e o índice de desempenho (Id). Através dos resultados obtidos pode-se afirmar que o método do forno elétrico e o método do forno de micro-ondas apresentaram desempenho ótimo quando comparados ao método padrão. O método das pesagens apresentou desempenho bom e muito bom. Também concluiu-se que o tempo de 20 minutos para o método do forno elétrico foi eficiente, significando redução no tempo para determinação da umidade. Para o método do forno de micro-ondas o tempo de 5 minutos de secagem foi suficiente, não diferindo estatisticamente do método padrão. O método das pesagens também se mostrou confiável na determinação da umidade do solo. Portanto, existe a possibilidade de usar os métodos alternativos para a determinação da umidade do solo.

Ground Penetrating Radar (GPR) is an effective tool to measure the geological properties. A lot of information can be interpreted from the GPR data, such as soil water content. One of the common approaches is to determine the apparent electrical permittivity from the transmission velocity of the impulse electromagnetic wave, and to use empirical relationships to estimate the soil water content. For example, Ferre equation & Topp equation are all expressing the relationship between soil water content and electrical permittivity. However, this method has some limitations; most notably the necessity to determine the velocity from a known depth to a reflecting surface. Therefore, another approach using the frequency dependent attenuation represented by a parameter called Q* was tested and studied in this thesis. The Q* method was evaluated using laboratory measurements, which consists of a series of experiments. A new empirical model was established using experiments where Q* was estimated from measurements on a soil sample with known water contents using two types of antennas (1.6 GHz & 2.3 GHz). Finally, the adaptability of Topp equation and Ferre equation were verified, and a new empirical equation was defined. What’s more, the other method using Q* was proved to be feasible.

Philosophiae Doctor - PhD / Mountainous areas are important water sources in many landscapes. An understanding of how mountainous catchments function is important particularly in semi-arid areas, where water shortages are prevalent. In addition to climate and physiographic factors, the hydrological responses of mountainous catchments can be influenced by land uses and land cover types. Although the general effects of land use and land cover types on hydrological processes are known, prediction of the specific effects in a given catchment is still problematic. This study characterized flowpaths, and hydrological responses to different land cover types in a semi-arid, mountainous Kromme River catchment (Eastern Cape province of South Africa), located in the Cape Fold Mountains of the Table Mountain Group (TMG) geological region.

Philosophiae Doctor - PhD / This thesis aimed at contributing knowledge on how the widespread changes in land use/cover resulting from increasing human population and their associated activities, are influencing hydrological responses in a sub-humid catchment. The study therefore hypothesised that reduced forest cover over time in favour of agricultural activities is altering hydrological processes of the catchment which is affecting the flow characteristics in a sub-humid catchment. The sub-humid catchment selected to investigate these issues is the Nyangores River Catchment in Kenya.

This study evaluated the effectiveness of chiselling and elemental sulfur fertilization in improving an upland and a swale range site with fine loamy, carbonatic, typic calcixeroll soils in the Ait Rbaa Perimeter of central Morocco. Ponding infiltration, soil water content on a mass basis of the 0- to 10-cm and 10- to 20-cm soil layers, peak season biomass production, and botanical composition were monitored during the two growing seasons following the treatments (1984/85 and 1985/86). Chiselling significantly improved infiltration on both sites, although the improvement was greater on the finer and less stony swale site, where chiselling resulted in more stable ridges. The land treatment also increased the average water content by weight of the 0- to 20-cm soil layer. The increase was more frequent on the upland site and most pronounced on its o- to 10-cm surface soil layer. In the chiselled treatments, average soil water content decreased with soil depth on the upland site while it increased on the swale site because of differential furrow stability and soil texture. Both the average infiltration rates of 5 cm of water and the average water content varied with sampling time, although generally in opposite directions. The application of elemental sulfur at the rates of 0, 30, and 60 kg ha-1 did not significantly affect any of the measured variables. Average peak season biomass production was 11% greater with chiselling. Chiselling also positively affected botanical composition on the upland site by depressing average forb proportion and increasing legume ratio in the first growing season. The gain in biomass does not seem to be high enough to strongly recommend chiselling in the Ait Rbaa Perimeter before performing an economic analysis of the operation.

京都大学 / 0048 / 新制・論文博士 / 博士(農学) / 乙第13181号 / 論農博第2860号 / 新制||農||1061(附属図書館) / 学位論文||H30||N5103(農学部図書室) / (主査)教授 小杉 緑子, 教授 北山 兼弘, 教授 舟川 晋也 / 学位規則第4条第2項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Forestry has been found to increase the accumulation of methyl mercury (MeHg), a highly neurotoxic compound, in forest soils. However, little is known about how forestry influences catchment processes that governs the mercury (Hg) methylation process. Logging residues are used in harvested catchments in stick roads to reduce soil disturbances caused by forestry machinery. Logging residues left on site after harvest have been suggested to act as a source of high-quality organic matter that stimulates the activity of the microorganisms that carry out the methylation of Hg. In addition, logging residues might influence the activity and abundance of methylating bacteria by reducing the temperature fluctuations in soils below residues and by increasing the soil moisture content. To evaluate the impact of logging residues on the accumulation of MeHg, an experimental field study was carried out in three sites, one in Uppland and two in Västerbotten. The concentration of MeHg was compared between soils covered with residues and soils without residues, and between the lower and upper parts residue piles. Logging residues were not found to influence the levels of MeHg in soils. However, an increased accumulation of MeHg was found in the lower part of residue piles. The accumulation of MeHg in the lower parts was accompanied by a reduced temperature amplitude and an increased water content compared to the upper part of the piles. The increased formation of MeHg might have been mediated by an increased water content in the lower part of the residue piles, possibly by increasing the abundance and activity of Hgmethylating microorganisms due to suboxic/anoxic conditions within biofilms around decomposing needles. The dissolved organic matter composition in soil water differed in soils below residues compared to without residues, but the organic matter signature in soil water under residues was not found to be compliant with an elevated mercury methylation rate. As MeHg accumulated in the lower part of residue piles could become mobilized and transferred to surface water, the suitability of using logging residues in stick roads depends on the location within the catchment. The removal of logging residues could prevent the potential mobilization of MeHg from residue piles. Though, as soil disturbances may cause an increased Hg methylation rate and mediate MeHg export to surface waters, other form of protection, e.g. logging mats, should be used if logging residues are not used to protect soils. / Mänsklig aktivitet har lett till förhöjda halter av kvicksilver (Hg) i atmosfären. Genom långväga transport och deposition har detta orsakat förhöjda halter i svensk natur. Den huvudsakliga exponeringsvägen av Hg för människan sker genom konsumtion av fisk. Halterna av Hg i svensk insjöfisk överstiger EU:s gränsvärden för god kemisk status samt Världshälsoorganisationens riktlinjer för konsumtion i majoriteten av svenska vatten. Ackumuleringen av Hg i biota sker främst i form av metylkvicksilver (MeHg) som är starkt neurotoxiskt. Avverkning av skog tros bidra till en ökad bildning av MeHg i skogsmark genom att skapa miljöer som gynnar etableringen och aktiviteten av de mikroorganismer som omvandlar icke-organiskt kvicksilver (Hg(II)) till organiskt kvicksilver (MeHg). Dessutom kan skogsbruk bidra till en ökad export av MeHg till följd av ändrade hydrologiska förhållanden samt markskador. En ökad bildning av MeHg är oönskad då mobilisering sedermera kan ske till vattendrag där MeHg kan ackumuleras i akvatisk biota. Dock är kunskapen om hur skogsbruk påverkar specifika processer som är av betydelse för metyleringen av Hg begränsad. Inom skogsbruk används avverkningsrester, bestående av till exempel grenar och toppar, i rishögar för att skydda marken mot körskador. Avverkningsrester som lämnas kvar på området efter avverkning tros bidra till en ökad metylering genom att utgöra en källa av högkvalitativt organiskt material vilket kan stimulera bakteriell aktivitet. Dessutom kan avverkningsrester bidra till en ökad metylering av Hg genom att minska temperaturfluktuationerna i mark täckt med ris samt öka markens vattenhalt, vilket kan bidra till en ökad etablering samt att stimulera aktiviteten av Hg-metylerande mikroorganismer. För att utvärdera effekten av avverkningsrester på ackumuleringen av MeHg genomfördes en experimentell fältstudie där koncentrationen av MeHg jämfördes i mark täckt med ris och mark utan ris. Dessutom undersöktes huruvida en ökad metylering kan ske i den nedre delen av riset, vilket skulle kunna möjliggöras av bakterier i biofilmer kring ris under nedbrytning. Koncentrationen MeHg var högre i den nedre delen av rishögarna jämfört med den övre delen. I den nedre delen av riset var temperaturfluktuationerna lägre och vattenhalten högre än i den övre delen av riset. Ackumuleringen av MeHg kan ha skett via biofilmer i de nedre delarna av riset, där tillgången till hög kvalitativt organiskt material samt mer syrefria förhållanden kan ha gynnat etableringen och aktiviteten av de bakterier som utför metyleringen av Hg. Däremot hade typen av marktäcke, dvs mark täckt med ris och mark utan ris, inte någon påverkan på metyleringen av Hg. Karaktären av organiskt material i markvatten skiljde sig mellan typ av marktäcke, men visar inte på att avverkningsrester utgör en källa av högkvalitativt organiskt material. Vattenhalten i mark under rishögar skiljde sig inte jämfört med mark utan ris, men temperaturen var lägre med mindre variation i mark under rishögar. Därmed visar resultatet på att avverkningsrester kan bidra till en ökad bildning av MeHg. En potentiell mobilisering av MeHg som bildats i rishögarna skulle därför kunna bidra till en ökad export av MeHg från avverkade områden. Användningen av avverkningsrester, för att skydda marken vid körning med skogsmaskiner, anses ändå vara fördelaktig för att minimera utläckage av MeHg. Körskador kan skapa stående vattensamlingar där MeHg kan bildas samt kompaktera mark och skapa snabba ytliga flödesvägar i området. Däremot tyder resultatet på att användningen bör ske med hänsyn till att förhindra eventuell transport av MeHg till vattendrag. Ifall avverkningsrester inte används för att motverka markskador bör ett substitut användas, exempelvis stock-mattor, då körskador kan bidra till en ökad metylering och mobilisering av MeHg. Dock saknas kunskap om eventuell mobilisering av MeHg från rishögar till vattendrag och detta bör utvärderas i framtida studier.