Thesis (M.S.)--University of Wisconsin--Madison, 1964. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 133-140.

Phosphorus and micronutrient (Fe, Mn, Cu & Zn) behaviour was investigated under flooded and aerated soil conditions, typical of paddy rice and wheat rotations in Pakistan. Pyrophosphate was used in small proportions with orthophosphate to investigate its effects on P and micronutrient, particular Zn availability, during both laboratory incubations and glass house experiments. Hydrolysis of pyrophosphate, its effects on P sorption by lime and different soils with or without added "organic acids" were also studied. Flooded conditions during both laboratory incubations and glass house trials greatly increased the extractability of soil P in comparison to controls and orthophosphate treated samples. Moist aerated conditions enhanced the sorption of applied P, with further sorption being observed in alternating flooded and moist aerated conditions. Increases in the extractability of soil P were related to iron oxidases/hydroxides. Soil Fe, Mn and Cu increased with flooding whereas soil Zn decreased. Soil P availability increased with the addition of lime, the 10% level being more effective than 5%, either due to increases in pH and/or due to precipitation of iron, the active site for P sorption. Pyrophosphate with or without added Zn decreased p sorption by lime and the soils studied, with the greatest effects being observed in the presence of lime. Added pyrophosphate, in the presence of lime, also maintained lower pH values in the solution compared with orthophosphate treated samples. Among the soils, pyrophosphate proved to be more effective when added to a calcareous Pakistani soil rather than the local soils (brown earth + brown podzolic). Added "organic acids", like extracts of soil and rice straw, decreased P sorption whereas the addition of (0.1M) citric acid increased it. Added Zn decreased P sorption by agricultural lime and the soils studied. In the presence of added pyrophosphate, sorption of Zn by agricultural lime decreased whereas sorption increased in soils.

O arroz irrigado está entre os principais cereais produzidos no mundo. Determinar a evapotranspiração (ET) para as grandes áreas de arroz irrigado é um desafio devido a pouca disponibilidade de dados. Diversos Modelos de ET vêm sendo desenvolvidos com a intenção de monitorar áreas agrícolas, porém poucos estudos experimentais são realizados sobre áreas de arroz irrigado. Este trabalho tem como objetivo geral estimar a ET sobre cultivos de arroz irrigado através de um modelo que utiliza informações meteorológicas in situ (Priestley-Taylor) e outro remoto (MOD16). O Priestley-Taylor (PT) é um modelo de ET que utiliza informações de temperatura do ar e componentes relacionadas ao balanço de energia, juntamente com um parâmetro adimensional α. O modelo MOD16 foi criado para monitorar a ET em grandes áreas, utilizando informações meteorológicas de um banco de dados de reanálise juntamente com dados remotos. Ambos os métodos não apresentam calibração e validação sobre áreas de arroz irrigado no Sul do Brasil. Neste trabalho validamos estes dois modelos a partir de dois sítios experimentais com medidas de ET através da técnica de Eddy Covariance. Os resultados encontrados nesta pesquisa mostraram-se satisfatórios quando comparado o método PT com dados experimentais, recomendando-se a utilização de 1,22 do parâmetro α. A simplificação no método PT realizada a partir das componentes do balanço de energia, com substituição pela variável de radiação global através de uma regressão linear, mostrou-se válida apresentando erros poucos expressivos, e com valor de 1,18 para parâmetro α. Já o modelo de ET MOD16 mostrou-se pouco preciso sobre as áreas de arroz irrigado. A validação de ET MOD16 foi realizada sobre uma área de 3 x 3 km e pixel central, resultando em menor subestimativa do modelo para o pixel central em relação aos dados de Eddy Covariance. Além disso, a correlação foi realizada em função das variáveis ambientais, encontrando maior correlação do dado experimental com as componentes do balando de energia, enquanto o MOD16 apresentou maior correlação com a temperatura do ar. Por fim, sugerem-se melhorias na parametrização da energia disponível no modelo de ET MOD16. Além disso, a aplicação do método simplificado de PT é indicada sobre áreas de arroz irrigado. / Irrigated rice is among principal produced cereals in the world. Determining the evapotranspiration (ET) for large areas of irrigated rice is a challenge task, due to poor data availability. Several ET models have been developed with the intention of monitoring agricultural areas, however few experimental studies are accomplished on areas of irrigated rice. This study aims to estimate ET on irrigated rice crops using a model which employs meteorological information in situ (Priestley-Taylor) and one remote (MOD16). Priestley-Taylor (PT) is a model of ET that uses air temperature and related components to the energy balance as information and a dimensionless parameter α. The MOD16 model was designed to monitor ET in large areas using meteorological information obtained from the reanalysis database together with remote data. Both methods do not present calibration and validation on areas of irrigated rice in Southern Brazil. In this work we validate these two models from two experimental sites with ET measurements employing the Eddy Covariance technique. The results found in this research was satisfactory when compared to the PT method with experimental data. It was suggested 1.22 for the α parameter. The simplification in the PT method performed from the components of the energy balance, with substitution for the global radiation variable using a linear regression. It was validated with few expressive errors, with a value of 1.18 for α parameter. On the other hand, the MOD16 model did not showed good accuracy on the areas of irrigated rice. The validation of ET MOD16 was performed over an area of 3 x 3 km and central pixel, resulting in a small underestimation of the model for the central pixel in relation to Eddy Covariance data. In addition, was performed the correlation in function of the environmental variables, finding a higher correlation of the experimental data with the components of the energy balance, while the MOD16 showed a high correlation with the air temperature. Finally, it was suggested improvements in the parameterization of the available energy in the model of ET MOD16, and to indicate the application of the simplified method of PT on the areas with irrigated rice.

O arroz irrigado está entre os principais cereais produzidos no mundo. Determinar a evapotranspiração (ET) para as grandes áreas de arroz irrigado é um desafio devido a pouca disponibilidade de dados. Diversos Modelos de ET vêm sendo desenvolvidos com a intenção de monitorar áreas agrícolas, porém poucos estudos experimentais são realizados sobre áreas de arroz irrigado. Este trabalho tem como objetivo geral estimar a ET sobre cultivos de arroz irrigado através de um modelo que utiliza informações meteorológicas in situ (Priestley-Taylor) e outro remoto (MOD16). O Priestley-Taylor (PT) é um modelo de ET que utiliza informações de temperatura do ar e componentes relacionadas ao balanço de energia, juntamente com um parâmetro adimensional α. O modelo MOD16 foi criado para monitorar a ET em grandes áreas, utilizando informações meteorológicas de um banco de dados de reanálise juntamente com dados remotos. Ambos os métodos não apresentam calibração e validação sobre áreas de arroz irrigado no Sul do Brasil. Neste trabalho validamos estes dois modelos a partir de dois sítios experimentais com medidas de ET através da técnica de Eddy Covariance. Os resultados encontrados nesta pesquisa mostraram-se satisfatórios quando comparado o método PT com dados experimentais, recomendando-se a utilização de 1,22 do parâmetro α. A simplificação no método PT realizada a partir das componentes do balanço de energia, com substituição pela variável de radiação global através de uma regressão linear, mostrou-se válida apresentando erros poucos expressivos, e com valor de 1,18 para parâmetro α. Já o modelo de ET MOD16 mostrou-se pouco preciso sobre as áreas de arroz irrigado. A validação de ET MOD16 foi realizada sobre uma área de 3 x 3 km e pixel central, resultando em menor subestimativa do modelo para o pixel central em relação aos dados de Eddy Covariance. Além disso, a correlação foi realizada em função das variáveis ambientais, encontrando maior correlação do dado experimental com as componentes do balando de energia, enquanto o MOD16 apresentou maior correlação com a temperatura do ar. Por fim, sugerem-se melhorias na parametrização da energia disponível no modelo de ET MOD16. Além disso, a aplicação do método simplificado de PT é indicada sobre áreas de arroz irrigado. / Irrigated rice is among principal produced cereals in the world. Determining the evapotranspiration (ET) for large areas of irrigated rice is a challenge task, due to poor data availability. Several ET models have been developed with the intention of monitoring agricultural areas, however few experimental studies are accomplished on areas of irrigated rice. This study aims to estimate ET on irrigated rice crops using a model which employs meteorological information in situ (Priestley-Taylor) and one remote (MOD16). Priestley-Taylor (PT) is a model of ET that uses air temperature and related components to the energy balance as information and a dimensionless parameter α. The MOD16 model was designed to monitor ET in large areas using meteorological information obtained from the reanalysis database together with remote data. Both methods do not present calibration and validation on areas of irrigated rice in Southern Brazil. In this work we validate these two models from two experimental sites with ET measurements employing the Eddy Covariance technique. The results found in this research was satisfactory when compared to the PT method with experimental data. It was suggested 1.22 for the α parameter. The simplification in the PT method performed from the components of the energy balance, with substitution for the global radiation variable using a linear regression. It was validated with few expressive errors, with a value of 1.18 for α parameter. On the other hand, the MOD16 model did not showed good accuracy on the areas of irrigated rice. The validation of ET MOD16 was performed over an area of 3 x 3 km and central pixel, resulting in a small underestimation of the model for the central pixel in relation to Eddy Covariance data. In addition, was performed the correlation in function of the environmental variables, finding a higher correlation of the experimental data with the components of the energy balance, while the MOD16 showed a high correlation with the air temperature. Finally, it was suggested improvements in the parameterization of the available energy in the model of ET MOD16, and to indicate the application of the simplified method of PT on the areas with irrigated rice.

O arroz irrigado está entre os principais cereais produzidos no mundo. Determinar a evapotranspiração (ET) para as grandes áreas de arroz irrigado é um desafio devido a pouca disponibilidade de dados. Diversos Modelos de ET vêm sendo desenvolvidos com a intenção de monitorar áreas agrícolas, porém poucos estudos experimentais são realizados sobre áreas de arroz irrigado. Este trabalho tem como objetivo geral estimar a ET sobre cultivos de arroz irrigado através de um modelo que utiliza informações meteorológicas in situ (Priestley-Taylor) e outro remoto (MOD16). O Priestley-Taylor (PT) é um modelo de ET que utiliza informações de temperatura do ar e componentes relacionadas ao balanço de energia, juntamente com um parâmetro adimensional α. O modelo MOD16 foi criado para monitorar a ET em grandes áreas, utilizando informações meteorológicas de um banco de dados de reanálise juntamente com dados remotos. Ambos os métodos não apresentam calibração e validação sobre áreas de arroz irrigado no Sul do Brasil. Neste trabalho validamos estes dois modelos a partir de dois sítios experimentais com medidas de ET através da técnica de Eddy Covariance. Os resultados encontrados nesta pesquisa mostraram-se satisfatórios quando comparado o método PT com dados experimentais, recomendando-se a utilização de 1,22 do parâmetro α. A simplificação no método PT realizada a partir das componentes do balanço de energia, com substituição pela variável de radiação global através de uma regressão linear, mostrou-se válida apresentando erros poucos expressivos, e com valor de 1,18 para parâmetro α. Já o modelo de ET MOD16 mostrou-se pouco preciso sobre as áreas de arroz irrigado. A validação de ET MOD16 foi realizada sobre uma área de 3 x 3 km e pixel central, resultando em menor subestimativa do modelo para o pixel central em relação aos dados de Eddy Covariance. Além disso, a correlação foi realizada em função das variáveis ambientais, encontrando maior correlação do dado experimental com as componentes do balando de energia, enquanto o MOD16 apresentou maior correlação com a temperatura do ar. Por fim, sugerem-se melhorias na parametrização da energia disponível no modelo de ET MOD16. Além disso, a aplicação do método simplificado de PT é indicada sobre áreas de arroz irrigado. / Irrigated rice is among principal produced cereals in the world. Determining the evapotranspiration (ET) for large areas of irrigated rice is a challenge task, due to poor data availability. Several ET models have been developed with the intention of monitoring agricultural areas, however few experimental studies are accomplished on areas of irrigated rice. This study aims to estimate ET on irrigated rice crops using a model which employs meteorological information in situ (Priestley-Taylor) and one remote (MOD16). Priestley-Taylor (PT) is a model of ET that uses air temperature and related components to the energy balance as information and a dimensionless parameter α. The MOD16 model was designed to monitor ET in large areas using meteorological information obtained from the reanalysis database together with remote data. Both methods do not present calibration and validation on areas of irrigated rice in Southern Brazil. In this work we validate these two models from two experimental sites with ET measurements employing the Eddy Covariance technique. The results found in this research was satisfactory when compared to the PT method with experimental data. It was suggested 1.22 for the α parameter. The simplification in the PT method performed from the components of the energy balance, with substitution for the global radiation variable using a linear regression. It was validated with few expressive errors, with a value of 1.18 for α parameter. On the other hand, the MOD16 model did not showed good accuracy on the areas of irrigated rice. The validation of ET MOD16 was performed over an area of 3 x 3 km and central pixel, resulting in a small underestimation of the model for the central pixel in relation to Eddy Covariance data. In addition, was performed the correlation in function of the environmental variables, finding a higher correlation of the experimental data with the components of the energy balance, while the MOD16 showed a high correlation with the air temperature. Finally, it was suggested improvements in the parameterization of the available energy in the model of ET MOD16, and to indicate the application of the simplified method of PT on the areas with irrigated rice.

Salinity intrusion, caused by global sea-level rise, is a major threat to paddy cultivation in the Mekong Delta of Vietnam (MKD). Salinity exposure reduces crop yields, increases soil salinity, and exacerbates fresh water scarcity, resulting in altered land use decisions and decreased paddy farming profitability. This study evaluates the effects of salinity intrusion on paddy yields and planted acreage, using a 21-year district-level panel dataset from the 13 provinces in the MKD. Specifically, we analyze the relationship between current salinity levels and paddy yield, as well as the relationship between lagged salinity levels and the paddy planted area. We examine these relationships across all districts, as well as for salinity-prone and non-salinity-prone districts and by proximity to the coast (20 km, 20-60 km, and 60+ km). The results indicate that salinity intrusion poses a significant challenge to paddy production in salinity-prone and coastal regions. Salinity level significantly and adversely affects paddy yields in salinity-prone and coastal districts. Similarly, high salinity levels in the past five years significantly reduce planted paddy acreage in these same regions. We also find that paddy yields in the MKD peaked in 2015 and have been declining since. The study highlights the regional differences in challenges associated with salinity intrusion in paddy production. Policymakers and agricultural managers need to take a region-specific approach to ensure that interventions are tailored to the specific needs and challenges faced by farmers. This entails supporting intensified paddy production in less salinity-prone areas and facilitating transitions to economically profitable alternatives to paddy in more salinity-prone areas. / Master of Science / Salinity intrusion, resulting from rising sea levels worldwide, poses a significant threat to paddy cultivation in the Lower Mekong Delta, Vietnam (MKD). The increased exposure to salinity adversely affects crop yields, exacerbates soil salinity levels, and contributes to freshwater scarcity. Consequently, this study aims to assess the effects of salinity intrusion on paddy yields and planted acreage in the MKD. By using a 21-year dataset covering thirteen provinces within the MKD, this study examines the relationship between current salinity levels and paddy yield, as well as the association between lagged salinity levels and the planted area of paddy crops. The analysis considers all districts within the region, distinguishing between salinity-prone and non-salinity-prone districts, as well as the proximity to the coast (20 km, 20-60 km, and 60+ km). The findings indicate that salinity intrusion presents a significant challenge to paddy production in both salinity-prone and coastal regions. High salinity levels substantially and adversely affect paddy yields in these districts. Furthermore, elevated salinity levels within the past five years significantly reduce the planted acreage of paddy crops in the same regions. Notably, paddy yields in the MKD reached their peak in 2015 and have been declining since. This study highlights the need for tailored strategies to address the diverse challenges faced by farmers in different regions. Policymakers and agricultural managers must support intensified rice production in areas that are less prone to salinity, while also promoting alternative crops in regions more vulnerable to salinity. By doing so, we can help sustain agricultural productivity and livelihoods in Vietnam's Mekong Delta, even in the face of salinity intrusion.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第20448号 / 農博第2233号 / 新制||農||1050(附属図書館) / 学位論文||H29||N5069(農学部図書室) / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 神﨑 護, 教授 北島 薫, 教授 柴田 昌三 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

Le delta du Rhône est une vaste plaine alluviale recouverte d’étangs et de lagunes, parsemée de cultures diverses, principalement du riz (21’100 ha en 2009, Centre Français du Riz, 2010). Des herbicides répandus en avril (pré levée, prétilachlor) et en juin (poste levée, bentazone ; MCPA et dichlorprop) sont utilisés dans la riziculture pour lutter contre les mauvaises herbes. L’étang de Vaccarès, qui est classé «réserve de biosphère» par l’UNESCO pour sa grande richesse biologique reçoit des pesticides directement issus des rizières par les canaux de drainage. D’un point de vue scientifique, peu d’études sont consacrées au devenir des pesticides dans les eaux estuariennes. En outre, la plupart de ces études ont été focalisées sur la photochimie bien que la biodégradation soit impliqué dans l’atténuation des pesticides. Alors le but de ce travail de thèse est de comprendre le devenir des herbicides de riziculture en évaluant le rôle de la photochimie direct et indirect et de la biodégradation. Nous avons développé donc un modèle capable de décrire la transformation de molécules organique par la voie photochimique dans les eaux estuariennes. Enfin nous avons déterminé les processus principaux impliqués dans l'atténuation rapide des herbicides de riziculture en Camargue. / The Ile de Camargue basin is the central part of the Rhône Delta in the south of France included between the two branches of the river. The higher parts of this area are agricultural lands, mainly rice fields, whereas the lower parts are lagoons and natural wetlands of international importance for biodiversity preservation.Bentazone, dichlorprop, and MCPA are post-emerging herbicides applied in rice fields from mid April to mid June. Rice fields grown under flooded conditions represent an environment where these conditions increase the potential for pesticides to transport in runoff from rice fields to non- target surface waters.To predict their fate in the surface waters of the Camargue and to asses their risk, it is necessary to understand their chemical reaction under environmental conditions.Reactive photoinduced species (RPS, hydroxyl radical HO., singlet oxygen 1O2 and dissolved organic matter triplet state) in estuarine waters (Vaccarès lagoon) were characterized experimentally to estimate the role of photochemistry in rice paddy. We then developed a kinetic model describing the solar photo-transformation of xenobiotic organic compounds induced by the three different photooxidants RPS. Sunlight photodegradation of bentazone, dichlorprop (DCPP), MCPA and alachlor (used as a surrogate for the similar Pretilachlor, pre-emergence herbicide) and microbial transformation were conducted experimentally to estimate near-surface half-lives in surface water. Parallel to the experimental study, an assessment of the elimination rates of those herbicides by sorption and sedimentation, and volatilization were obtained by the model MASAS (Modelling of Anthropogenic Substances in Aquatic Systems).The half-lives of the herbicides obtained experimentally were then compared with those obtained from field data. This allowed to assessing the main processes involved in the attenuation of herbicide concentrations.

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