No description available.

Honors project (B.A.) -- Carson-Newman College, 2009. / Project advisor: Dr. Christine Dalton. Includes bibliographical references (p. 40-41).

A extração de água do solo pelas plantas esta intimamente relacionada com a produtividade das culturas. O objetivo do presente estudo foi avaliar o desempenho das funções de redução de Jong Van Lier et al. (2008) e de Feddes, Kowalik e Zaradny (1978) na estimativa da extração de água por plantas de soja sob condições úmidas. A primeira e formalizada a partir de modelos microscópicos de extração de água e presume um potencial da água na superfície da raiz constante com a profundidade do sistema radicular, que e estimado pela transpiração da planta. A segunda e uma função de redução empírica, largamente utilizada em simulações de extração de água que não considera o mecanismo de compensação. O desempenho de ambas as funções de redução foi analisado através das variáveis (potencial e conteúdo da água no solo) simuladas pelo modelo agrohidrológico SWAP (Soil Water Plant Atmosphere). Um experimento foi conduzido em uma área do Campus da Escola Superior de Agricultura \\Luiz de Queiroz\". O conteúdo de água do solo e potencial matricial foram monitorados ao longo ciclo da cultura nas profundidades de 0,05, 0,15 e 0,30 m. Os dados diários das variáveis meteorológicas requeridas pelo SWAP foram obtidos do posto meteorológico da ESALQ, que dista, aproximadamente, 50 m do experimento. De acordo com os resultados obtidos, as funções de redução de transpiração apresentaram diferentes estimativas de distribuições temporais de extração de água ao longo da profundidade do solo. Essa diferença foi devido principalmente ao fato de a função de redução de Feddes, Kowalik e Zaradny (1978) não considerar o mecanismo de compensação de extração de água do solo. Em conseqüência, a função de redução diminuiu drasticamente o potencial matricial do solo nas camadas superficiais, em desacordo com as medições. A função de redução de Jong Van Lier et al. (2008) distribuiu a extração de água do solo regida pela distribuição do potencial de fluxo matricial. Mesmo nas condições úmidas ocorridas durante o período experimental, a distribuição radicular não influenciou na distribuição da extração de água do solo pelo modelo. Em alguns dias, o modelo extraiu toda a água demandada pela transpiração de apenas uma camada de solo (espessura de 1 cm). Esse comportamento simulado foi atribuído ao fato de a função de redução considerar um potencial de fluxo matricial constante com a profundidade, por desconsiderar a resistência radicular. Comparando tanto os valores do potencial matricial, quanto os do conteúdo de água do solo estimados pelo modelo SWAP para as três profundidades analisadas com os dados experimentais, a função de redução de Jong Van Lier (2008) apresentou desempenho superior ao da func~ao de Feddes, Kowalik e Zaradny (1978) . / Root water extraction is intrinsically associated to crop yield. In this work, we assessed the performance of Jong Van Lier et al. (2008) and Feddes, Kowalik e Zaradny (1978) reduction functions on estimating root water extraction by a soybean crop under nonlimiting soil hydraulic conditions. The rst reduction function is based on microscopic root water extraction models and assumes a depth-independent value of root surface pressure head, which is determined by plant transpiration. The latter is a classical and widely used empirical reduction function that does not take into consideration any compensation mechanism. The performance of both reduction functions was evaluated by means of simulated variables (soil water content and pressure head) by the agrohydrological model SWAP (Soil Water Plant Atmosphere). A eld experiment was carried out at the Escola Superior de Agricultura \\Luiz de Queiroz\" campus in Piracicaba, Brazil. Soil water content and pressure head was monitored during the entire crop cycle at 0.5, 0.15 and 0.30 m depths. Daily weather variables required by the SWAP model were obtained from the campus weather station, located at 50 m from the experiment. According to the results, the reduction functions presented dierent temporal root water extraction patterns along depth. This dierence occurred mainly because Feddes, Kowalik e Zaradny (1978) reduction function does not take into consideration a compensation mechanism. Thus, unlike in the eld measurements, pressure head in the top layers was substantially reduced. The Jong Van Lier (2008) reduction function distributed soil water extraction according to matric ux potential. Even under the wet (non-limiting) conditions during the experiment, root density did not in uence the root water extraction pattern predicted by the model. At some days, the reduction function extracted all the water for transpiration from only one soil layer (1 cm layer thickness). This simulated behavior was attributed to the depth-independent matric ux potential assumed by the reduction function as a consequence of disregarding internal root resistance. Comparing both pressure head and soil water content observations estimated by SWAP for the three analyzed depths to the experimental data, the De Jong van Lier (2008) reduction function showed a better performance than the Feddes, Kowalik e Zaradny (1978) reduction function.

A extração de água do solo pelas plantas esta intimamente relacionada com a produtividade das culturas. O objetivo do presente estudo foi avaliar o desempenho das funções de redução de Jong Van Lier et al. (2008) e de Feddes, Kowalik e Zaradny (1978) na estimativa da extração de água por plantas de soja sob condições úmidas. A primeira e formalizada a partir de modelos microscópicos de extração de água e presume um potencial da água na superfície da raiz constante com a profundidade do sistema radicular, que e estimado pela transpiração da planta. A segunda e uma função de redução empírica, largamente utilizada em simulações de extração de água que não considera o mecanismo de compensação. O desempenho de ambas as funções de redução foi analisado através das variáveis (potencial e conteúdo da água no solo) simuladas pelo modelo agrohidrológico SWAP (Soil Water Plant Atmosphere). Um experimento foi conduzido em uma área do Campus da Escola Superior de Agricultura \\Luiz de Queiroz\". O conteúdo de água do solo e potencial matricial foram monitorados ao longo ciclo da cultura nas profundidades de 0,05, 0,15 e 0,30 m. Os dados diários das variáveis meteorológicas requeridas pelo SWAP foram obtidos do posto meteorológico da ESALQ, que dista, aproximadamente, 50 m do experimento. De acordo com os resultados obtidos, as funções de redução de transpiração apresentaram diferentes estimativas de distribuições temporais de extração de água ao longo da profundidade do solo. Essa diferença foi devido principalmente ao fato de a função de redução de Feddes, Kowalik e Zaradny (1978) não considerar o mecanismo de compensação de extração de água do solo. Em conseqüência, a função de redução diminuiu drasticamente o potencial matricial do solo nas camadas superficiais, em desacordo com as medições. A função de redução de Jong Van Lier et al. (2008) distribuiu a extração de água do solo regida pela distribuição do potencial de fluxo matricial. Mesmo nas condições úmidas ocorridas durante o período experimental, a distribuição radicular não influenciou na distribuição da extração de água do solo pelo modelo. Em alguns dias, o modelo extraiu toda a água demandada pela transpiração de apenas uma camada de solo (espessura de 1 cm). Esse comportamento simulado foi atribuído ao fato de a função de redução considerar um potencial de fluxo matricial constante com a profundidade, por desconsiderar a resistência radicular. Comparando tanto os valores do potencial matricial, quanto os do conteúdo de água do solo estimados pelo modelo SWAP para as três profundidades analisadas com os dados experimentais, a função de redução de Jong Van Lier (2008) apresentou desempenho superior ao da func~ao de Feddes, Kowalik e Zaradny (1978) . / Root water extraction is intrinsically associated to crop yield. In this work, we assessed the performance of Jong Van Lier et al. (2008) and Feddes, Kowalik e Zaradny (1978) reduction functions on estimating root water extraction by a soybean crop under nonlimiting soil hydraulic conditions. The rst reduction function is based on microscopic root water extraction models and assumes a depth-independent value of root surface pressure head, which is determined by plant transpiration. The latter is a classical and widely used empirical reduction function that does not take into consideration any compensation mechanism. The performance of both reduction functions was evaluated by means of simulated variables (soil water content and pressure head) by the agrohydrological model SWAP (Soil Water Plant Atmosphere). A eld experiment was carried out at the Escola Superior de Agricultura \\Luiz de Queiroz\" campus in Piracicaba, Brazil. Soil water content and pressure head was monitored during the entire crop cycle at 0.5, 0.15 and 0.30 m depths. Daily weather variables required by the SWAP model were obtained from the campus weather station, located at 50 m from the experiment. According to the results, the reduction functions presented dierent temporal root water extraction patterns along depth. This dierence occurred mainly because Feddes, Kowalik e Zaradny (1978) reduction function does not take into consideration a compensation mechanism. Thus, unlike in the eld measurements, pressure head in the top layers was substantially reduced. The Jong Van Lier (2008) reduction function distributed soil water extraction according to matric ux potential. Even under the wet (non-limiting) conditions during the experiment, root density did not in uence the root water extraction pattern predicted by the model. At some days, the reduction function extracted all the water for transpiration from only one soil layer (1 cm layer thickness). This simulated behavior was attributed to the depth-independent matric ux potential assumed by the reduction function as a consequence of disregarding internal root resistance. Comparing both pressure head and soil water content observations estimated by SWAP for the three analyzed depths to the experimental data, the De Jong van Lier (2008) reduction function showed a better performance than the Feddes, Kowalik e Zaradny (1978) reduction function.

A major problem in irrigated agriculture in the Western U.S. is the gradual accumulation of salinity in the plant root zone. These nonuniformly saline soils contain increasing amounts of salinity with depth, and salt accumulation is accelerated in situations where leaching is minimized. Root growth and thus plant yield is limited in these soils due to decreased water uptake. We studied the root growth of two subpopulations of alfalfa differing in their ability to produce fibrous roots to determine if altering root morphology would increase plant yield and water extraction, in an irrigated saline soil. Soil profiles for a control and three treatments with increasing salinity were packed in to PVC cylinders fitted with a flat window down one side for root measurements. A single alfalfa plant was grown from seed in each cylinder, and irrigated with water enriched primarily in sulfate salts. Alfalfa plants were grown for five successive harvests in a greenhouse, and water extraction was measured in the control and high Salinity treatment by time-domain reflectometry. Final electrical conductivities of the soil ranged from 3.0 to 23 dS m-1. The yield of the high fibrous root subpopulation was not reduced by the soil salinity by the fifth harvest, while that of the low fibrous subpopulation was reduced 22%. Root growth of the high fibrous subpopulation was significantly increased by as much as 54% in the upper 30 cm of the root zone, compared to that of the low fibrous subpopulation. Water extraction was higher in the upper, least saline portion of the root zone for the high fibrous root subpopulation. The results of this study support the use of alfalfa with increased fibrous root production under saline irrigation with minimal leaching.

The purpose of this study was to develop a model to predict water extraction patterns and therefore salt distribution patterns in a one dimensional homogeneous soil profile for a specified root distribution . Water extraction was simulated as a function of the total potential and the root density at any level of the profile. Salt redistribution caused by irrigation was simulated by assuming a partial and proportional displacement of the water in each soil layer. A computer program was written for the model in Fortran language and implemented on the Vax. To evaluate the performance of the model, test studies were carried out in the laboratory using two lysimeters and wheat as a crop. A neutron probe and the four-probe electrode method were used to follow the change in the soil moisture and the salinity in the profile during the growing season. Comparisons were made between the measured and simulated values of water content and salinity. Application of the model results and recommendations for further research were suggested to improve the performance of the model.

No description available.

New vigorous regulations have been established for decreasing the allowable formaldehyde emissions from nonstructural wood based composites. Two main sources of formaldehyde emission in non-structural wood based composites are adhesive and wood. Adhesives are quite well known and great efforts have been conducted to decrease their formaldehyde content; however formaldehyde emission from wood has received little attention and it is not completely understood. Wood-borne formaldehyde emission exists in a complex equilibrium in wood matrix. The reaction between formaldehyde and wood hydroxyl groups/water can hinder the complete formaldehyde extraction. In order to have a complete formaldehyde extraction, a stronger nucleophile than hydroxyl and water groups is needed. In this study cross-linked poly (allylamine) (PAA) beads were synthesized and used as a strong nucleophile to extract all the biogenic and synthetic free-formaldehyde within the woody matrix of never-heated and heat-treated Virginia pines; the results were compared to simple water extraction. A new formaldehyde capturing device was also developed using a serum bottle. Results showed that there was no advantage of using PAA beads over simple water extraction for extracting woody matrix free-formaldehyde. This means that simple water extraction can extract all the free-formaldehyde from the woody matrix. It was also found that thermal treatment resulted in generating more wood-borne formaldehyde. The other important finding was the new developed formaldehyde capturing device. The device was very promising for detecting wood-borne formaldehyde from very small pieces of wood (5-70 mg) and can be very useful in future studies. / Master of Science

A facilidade com que uma raiz pode extrair água do solo é determinada pela condutividade hidráulica do solo e gradiente do potencial energético da água, ambos função do teor de água no solo. Nessa dissertação descreve-se o teste experimental de um modelo de extração e de partição da água do solo pelo sistema radicular de uma planta cujo sistema radicular se divide entre camadas de solo com propriedades hidráulicas contrastantes. O estudo foi conduzido em ambiente protegido com plantas de sorgo (Sorghum bicolor (L.) Moench) cultivadas em lisímetros com dois compartimentos separados fisicamente (splitpot). Quatro desses lisímetros foram construídos, preenchidos com material de dois tipos de solo de diferentes classes texturais (um solo de textura média - AR e outro de textura argilosa - AG). Durante um mês e meio foi aplicado um regime hídrico alternando a irrigação entre os compartimentos. O teor de água nos compartimentos dos lisímetros foi monitorado com TDR e tensiômetros. O material dos dois solos foi analisado conforme metodologia padrão quanto às suas propriedades de retenção e condução da água. A densidade radicular foi determinada por pesagem no fim do experimento, tendo ficado em torno de duas vezes maior no solo AR do que no AG. Foi possível observar que a extração de água ocorreu preferencialmente do compartimento do lisímetro com maior potencial de fluxo matricial. Em certas ocasiões houve transferência de água do lado de maior ao lado de menor potencial de fluxo matricial, com a liberação da água ao solo pelo sistema radicular (hydraulic lift). Em relação ao modelo, para compensar pelo efeito da heterogeneidade da distribuição radicular, da atividade radicular e do contato solo-raiz, incluiu-se um fator empírico f de correção no modelo. O valor de f foi determinado por ajuste numérico procurando-se uma correlação máxima entre modelo e observação nos quatro lisímetros. Para os solos AR e AG, os valores de f assim determinados foram 0,01506 e 0,003713, respectivamente. O modelo testado descreveu razoavelmente bem as observações com a utilização desses valores de f. / Root water extraction is determined by soil hydraulic conductivity and water potential gradients, both dependent on soil water content. In this dissertation the experimental test of a root water extraction and partition model is described for a plant whose root system is divided over soil layers with distinct hydraulic properties. An experiment was conducted in a greenhouse with Sorghum (Sorghum bicolor (L.) Moench) plants growing in split-pot lysimeters containing two physically divided compartments. Four of these lysimenters were built, filled with material from two soils with different texture (a médium textured soil - AR and a clayey soil - AG). During a month and a half a water regime was applied alternating the irrigation among the compartments. The soil water content in the compartments was measured with TDR and tensiometer equipment. Soil hydraulic properties retention and conductivity were analyzed by standard methods. Root density was determined by weighing at the end of the experiment, resulting in values twice as high in soil AR compared to soil AG. It could be observed that water extraction occurred preferentially from the lysimeter compartments with the highest matric flux potential. At certain occasions, water transfer from the compartment with higher matric flux potential to the lower one was observed, transferring water from root to soil (hydraulic lift). Referring to the model, in order to compensate for root distribution heterogeneity, root activity and soil-root contact, an empirical factor f was added to the model. Its value was determined by a numerical fitting procedure aiming the highest correlation between model and observation in the four lysimeters. For soils AR and AG, the values of f determined were 0.01506 and 0.003713, respectively. The tested model described the observations reasonably well using these values of f.

A facilidade com que uma raiz pode extrair água do solo é determinada pela condutividade hidráulica do solo e gradiente do potencial energético da água, ambos função do teor de água no solo. Nessa dissertação descreve-se o teste experimental de um modelo de extração e de partição da água do solo pelo sistema radicular de uma planta cujo sistema radicular se divide entre camadas de solo com propriedades hidráulicas contrastantes. O estudo foi conduzido em ambiente protegido com plantas de sorgo (Sorghum bicolor (L.) Moench) cultivadas em lisímetros com dois compartimentos separados fisicamente (splitpot). Quatro desses lisímetros foram construídos, preenchidos com material de dois tipos de solo de diferentes classes texturais (um solo de textura média - AR e outro de textura argilosa - AG). Durante um mês e meio foi aplicado um regime hídrico alternando a irrigação entre os compartimentos. O teor de água nos compartimentos dos lisímetros foi monitorado com TDR e tensiômetros. O material dos dois solos foi analisado conforme metodologia padrão quanto às suas propriedades de retenção e condução da água. A densidade radicular foi determinada por pesagem no fim do experimento, tendo ficado em torno de duas vezes maior no solo AR do que no AG. Foi possível observar que a extração de água ocorreu preferencialmente do compartimento do lisímetro com maior potencial de fluxo matricial. Em certas ocasiões houve transferência de água do lado de maior ao lado de menor potencial de fluxo matricial, com a liberação da água ao solo pelo sistema radicular (hydraulic lift). Em relação ao modelo, para compensar pelo efeito da heterogeneidade da distribuição radicular, da atividade radicular e do contato solo-raiz, incluiu-se um fator empírico f de correção no modelo. O valor de f foi determinado por ajuste numérico procurando-se uma correlação máxima entre modelo e observação nos quatro lisímetros. Para os solos AR e AG, os valores de f assim determinados foram 0,01506 e 0,003713, respectivamente. O modelo testado descreveu razoavelmente bem as observações com a utilização desses valores de f. / Root water extraction is determined by soil hydraulic conductivity and water potential gradients, both dependent on soil water content. In this dissertation the experimental test of a root water extraction and partition model is described for a plant whose root system is divided over soil layers with distinct hydraulic properties. An experiment was conducted in a greenhouse with Sorghum (Sorghum bicolor (L.) Moench) plants growing in split-pot lysimeters containing two physically divided compartments. Four of these lysimenters were built, filled with material from two soils with different texture (a médium textured soil - AR and a clayey soil - AG). During a month and a half a water regime was applied alternating the irrigation among the compartments. The soil water content in the compartments was measured with TDR and tensiometer equipment. Soil hydraulic properties retention and conductivity were analyzed by standard methods. Root density was determined by weighing at the end of the experiment, resulting in values twice as high in soil AR compared to soil AG. It could be observed that water extraction occurred preferentially from the lysimeter compartments with the highest matric flux potential. At certain occasions, water transfer from the compartment with higher matric flux potential to the lower one was observed, transferring water from root to soil (hydraulic lift). Referring to the model, in order to compensate for root distribution heterogeneity, root activity and soil-root contact, an empirical factor f was added to the model. Its value was determined by a numerical fitting procedure aiming the highest correlation between model and observation in the four lysimeters. For soils AR and AG, the values of f determined were 0.01506 and 0.003713, respectively. The tested model described the observations reasonably well using these values of f.