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Qureshi, Suhail Ahmad. "Soil water balance of intercropped corn under water table management." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23289.
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A one year water table management field study was conducted on a Soulanges sandy loam soil in Soulanges county, Quebec. Two controlled water table levels, i.e. 0.5 m and 0.75 m from the soil surface, as well as free outlet conventional drainage treatments were established in monocropped corn (Zea mays L.) and corn intercropped with ryegrass (Lolium multiflorum Lam) plots.Cropping system showed no significant effects on evapotranspiration, and on soil moisture distribution. It was observed that the 0.5 m and 0.75 m controlled water tables (CWT) provided the same soil moisture trends in both cropping systems. The soil moisture was always higher in controlled water table plots compared to freely drained plots. The water use efficiency of 0.75 m CWT in both cropping systems was high compared to 0.5 m CWT.
The soil moisture contents at three depths were only 2% to 10% less in intercropped plots compared to monocropped plots. The soil moisture was 12 to 13% higher in CWT plots compared to freely drained plots for both cropping systems. The soil moisture in 0.5 m CWT and 0.75 m CWT plots was not significantly different. The average water table levels in monocropped plots were not significantly different from intercropped plots.
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Al-Ali, Mahmoud. "Soil water conservation and water balance model for micro-catchment water harvesting system." Thesis, Loughborough University, 2012. https://dspace.lboro.ac.uk/2134/10941.
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A simple water balance model was applied to a micro-catchment water harvesting system for a semi-arid area in the North-Eastern part of Jordan. Two Negarim micro-catchment water harvesting systems were built at Al-Khanasri research station. A Randomized complete block design (RCBD) in factorial combination was used with six treatments and three replicates. Each plot was divided into two parts; a runoff area, and a run-on area. Two different treatments were used for the catchment area, these were: compacted (T1) and Natural treatments (T2). Three treatments were used for the run-on area, these were: disturbed (S1), stones (S2), and crop residue mulch (S3). Soil water content was measured over a depth of 0-1 m during the seasons 96-97 in these micro-catchments. In this model; daily rainfall, runoff, and evaporation were used. Runoff was calculated by the curve number method; evaporation was calculated by the Penman equation, the Priestley and Taylor method and the Class A pan approach. The least squares method was used for optimizing model parameters. The performance of the model was assessed by different criteria, such as root mean square error, relative root mean square error, coefficient of determination and the Nash-Sutcliffe efficiency method. The performance of the micro-catchments system was also evaluated. Results showed that with limited but reliable hydrological data good agreement between predicted and observed values could be obtained. The ratio of water storage in a one meter soil depth to the rainfall falling on each catchment indicated that T1S2 and T1S3 have the highest values in size1 plots while T2S1 and T2S2 have the highest values in size 2 plots. Modelling results showed that for all the size 1 plots, the required ratio of the cultivated to catchment area, (C/CA), required to ensure sufficient harvested water, was less than the actual ratio used in the experimental design. For the size 2 plots this was only true for the T1 treatments. Consequently for the majority of plot sizes and treatments, the results showed that a smaller catchment area is capable of providing sufficient harvested water to meet crop growth requirements. The experimental ratio was based on a typical yearly design rainfall for the region having either a 50% or 67% probability of occurrence. Results also indicated that using stones and crop residue as mulch on the soil surface in the cultivated area was effective in decreasing the evaporation rate. S3 was more efficient than S2 as it stored more water due to the higher infiltration rate (12.4 cm/hr) when compared to S2 (4.1 cm/hr).
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Buchanan, Margaret MacNeill. "Soil Water Flow and Irrigated Soil Water Balance in Response to Powder River Basin Coalbed Methane Product Water." Thesis, Montana State University, 2005. http://etd.lib.montana.edu/etd/2005/buchanan/BuchananM0505.pdf.
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A repacked soil columns experiment and a series of computer soil water balance simulations were conducted to examine potential impacts of coalbed methane (CBM) water from Montana's Powder River Basin (PRB) on soil water flow and water balance in PRB soils. CBM water is often high in sodium, which may separate soil clay particles, particularly after soil exposure to low-salinity rainfall or snowmelt, and when soils contain expansible smectite clay minerals. Aggregates in soils exposed to sodic water may swell and slake, and clays and other fine particles may disperse, clogging soil pores and slowing or preventing soil water flow. In the soil columns experiment, A and B horizon materials from sandy loam, silt loam, and clay loam soils were pre-treated with water having salinity and sodicity typical of PRB CBM water or of Powder River (PR) water currently used for irrigation in the basin. Tension infiltrometer measurements were used to determine infiltration flux, first using pre-treatment water, and subsequently deionized (DI) water, simulating rainwater. Measurements were compared by pre-treatment water, horizon, and soil type. Under pre-treatment water testing, the sandy loam and clay loam soils pre-treated with CBM water exhibited smaller infiltration flux values than when pre-treated with PR water. Only the sandy loam soil showed a greater decrease in infiltration flux with DI water on soils pre-treated with CBM relative to PR water pre-treated soils. There was no difference in infiltration flux decrease with DI water between A and B horizon soils, or between smectite and non-smectite soils. The soil water balance numerical simulations modeled potential effects of sodic irrigation waters on sandy loam, silt loam, clay loam and silty clay PRB soils under sprinkler or flood irrigation, during one growing season. Baseline soil water retention functions were constructed for the five soils, and adjusted via trends identified in the literature to create five additional functions for each soil, simulating exposure to five increasingly sodic irrigation waters. Simulation results showed greater impact of sodic irrigation under flood than sprinkler irrigation. The fine sandy loam and silty clay loam soils exhibited the fewest changes in water balance partitioning, while the silt loam and silty clay soils showed the greatest changes, especially in increased runoff and reduced transpiration.
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Oliveira, Paulo Tarso Sanches de. "Water balance and soil erosion in the Brazilian Cerrado." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/18/18138/tde-16012015-170452/.
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Deforestation of the Brazilian savanna (Cerrado) region has caused major changes in hydrological processes. These changes in water balance and soil erosion are still poorly understood, but are important for making land management decisions in this region. Therefore, it is necessary to understand the magnitudes of hydrological processes and soil erosion changes on local, regional and continental scales, and the consequences that are generated. The main objective of the study presented in this doctoral thesis was to better understand the mechanism of hydrological processes and soil erosion in the Cerrado. To achieve that, I worked with different scales (hillslope, watershed and continental) and using data from experimental field, laboratory, and remote sensing. The literature review reveals that the annual rainfall erosivity in Brazil ranges from 1672 to 22,452 MJ mm ha-1 h-1 yr-1. The smallest values are found in the northeastern region, and the largest in the north and the southeastern region. I found that the canopy interception may range from 4 to 20% of gross precipitation and stemflow around 1% of gross precipitation in the cerrado. The average runoff coefficient was less than 1% in the plots under cerrado and that the deforestation has the potential to increase up to 20 fold the runoff coefficient value. The results indicate that the Curve Number method was not suitable to estimate runoff under undisturbed Cerrado, bare soil (hydrologic soil group A), pasture, and millet. Therefore, in these cases the curve number is inappropriate and the runoff is more aptly modeled by the equation Q = CP, where C is the runoff coefficient. The water balance from the remote sensing data across the Brazilian Cerrado indicates that the main source of uncertainty in the estimated runoff arises from errors in the TRMM precipitation data. The water storage change computed as a residual of the water budget equation using remote sensing data (TRMM and MOD16) and measured discharge data shows a significant correlation with terrestrial water storage change obtained from the GRACE data. The results show that the GRACE data may provide a satisfactory representation of water storage change for large areas in the Cerrado. The average annual soil loss in the plots under bare soil and cerrado were 15.25 t ha-1 yr-1 and 0.17 t ha-1 yr-1, respectively. The Universal Soil Loss Equation cover and management factor (C-factor) for the plots under native cerrado vegetation was 0.013. The results showed that the surface runoff, soil erosion and C-factor for the undisturbed Cerrado changes between seasons. The greatest C-factor values were found in the summer and fall. The results found in this doctoral thesis provide benchmark values of the water balance components and soil erosion in the Brazilian Cerrado that will be useful to evaluate past and future land cover and land use changes for this region. In addition, I conclude that the remote sensing data are useful to evaluate the water balance components over Cerrado regions, identify dry periods, and assess changes in water balance due to land cover and land use change.O desmatamento nas regiões de Cerrado tem causado intensas mudanças nos processos hidrológicos. Essas mudanças no balanço hídrico e erosão do solo são ainda pouco entendidas, apesar de fundamentais na tomada de decisão de uso e manejo do solo nesta região. Portanto, torna-se necessário compreender a magnitude das mudanças nos processos hidrológicos e de erosão do solo, em escalas locais, regionais e continentais, e as consequências dessas mudanças. O principal objetivo do estudo apresentado nesta tese de doutorado foi de melhor entender os mecanismos dos processos hidrológicos e de erosão do solo no Cerrado Brasileiro. Para tanto, utilizou-se diferentes escalas de trabalho (vertentes, bacias hidrográficas e continental) e usando dados experimentais in situ, de laboratório e a partir de sensoriamento remoto. O estudo de revisão de literatura indica que a erosividade da chuva no Brasil varia de 1672 to 22,452 MJ mm ha-1 h-1 yr-1. Os menores valores encontram-se na região nordeste e os maiores nas regiões norte e sudeste do Brasil. Verificou-se que os valores de interceptação da chuva variam de 4 a 20% e o escoamento pelo tronco aproximadamente 1% da precipital total no cerrado. O coeficiente de escoamento superficial foi menor que 1% nas parcelas de cerrado e o desmatamento tem o potencial de aumentar em até 20 vezes esse valor. Os resultados indicam que o método Curve Number não foi adequado para estimar o escoamento superficial nas áreas de cerrado, solo exposto (grupo hidrológico do solo A), pastagem e milheto. Portanto, nesses casos o uso do CN é inadequado e o escoamento superficial é melhor estimado a partir da equação Q = CP, onde C é o coeficiente de escoamento superficial. O balanço hídrico a partir de dados de sensoriamento remoto para todo o Cerrado Brasileiro indica que a principal fonte de incerteza na estimativa do escoamento superficial ocorre nos dados de precipitação do TRMM. A variação de água na superfície terrestre calculada como o residual da equação do balanço hídrico usando dados de sensoriamento remoto (TRMM e MOD16) e valores observados de vazão mostram uma correlação significativa com os valores de variação de água na superfície terrestre provenientes dos dados do GRACE. Os dados do GRACE podem representar satisfatoriamente a variação de água na superfície terrestre para extensas regiões do Cerrado. A média anual de perda de solo nas parcelas de solo exposto e cerrado foram de 15.25 t ha-1 yr-1 and 0.17 t ha-1 yr-1, respectivamente. O fator uso e manejo do solo (fator C) da Universal Soil Loss Equation para o cerrado foi de 0.013. Os resultados mostraram que o escoamento superficial, erosão do solo e o fator C na área de cerrado variam de acordo com as estações. Os maiores valores do fator C foram encontrados no verão e outono. Os resultados encontrados nesta tese de doutorado fornecem valores de referência sobre os componentes do balanço hídrico e erosão do solo no Cerrado, que podem ser úteis para avaliar o uso e cobertura do solo atual e futuro. Além disso, conclui-se que os dados de sensoriamento remoto apresentam resultados satisfatórios para avaliar os componentes do balanço hídrico no Cerrado, identificar os períodos de seca e avaliar as alterações no balanço hídrico devido à mudanças de uso e cobertura do solo.
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Haigh, R. A. "Water balance and water quality studies in an underdrained clay soil catchment." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371543.
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Mhlauli, Ntuthuzelo Columbus. "Growth analysis and soil water balance of selected vegetable crops." Diss., University of Pretoria, 2000. http://hdl.handle.net/2263/26200.
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Please read the abstract in the section 00front of this documentDissertation (M Inst Agrar (Horticulture Science))--University of Pretoria, 2000.
Plant Production and Soil Science
unrestricted
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Chen, Liping. "Soil Characteristics Estimation and Its Application in Water Balance Dynamics." Thesis, University of North Texas, 2008. https://digital.library.unt.edu/ark:/67531/metadc9789/.
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This thesis is a contribution to the work of the Texas Environmental Observatory (TEO), which provides environmental information from the Greenbelt Corridor (GBC) of the Elm Fork of the Trinity River. The motivation of this research is to analyze the short-term water dynamic of soil in response to the substantial rainfall events that occurred in North Texas in 2007. Data collected during that year by a TEO soil and weather station located at the GBC includes precipitation, and soil moisture levels at various depths. In addition to these field measurements there is soil texture data obtained from lab experiments. By comparing existing water dynamic models, water balance equations were selected for the study as they reflect the water movement of the soil without complicated interrelation between parameters. Estimations of water flow between soil layers, infiltration rate, runoff, evapotranspiration, water potential, hydraulic conductivity, and field capacity are all obtained by direct and indirect methods. The response of the soil at field scale to rainfall event is interpreted in form of flow and change of soil moisture at each layer. Additionally, the analysis demonstrates that the accuracy of soil characteristic measurement is the main factor that effect physical description. Suggestions for model improvement are proposed. With the implementation of similar measurements over a watershed area, this study would help the understanding of basin-scale rainfall-runoff modeling.
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Chen, Liping Acevedo Miguel Felipe. "Soil characteristics estimation and its application in water balance dynamics." [Denton, Tex.] : University of North Texas, 2008. http://digital.library.unt.edu/permalink/meta-dc-9789.
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Mbarushimana, Kagabo Desire. "Modelling the soil water balance of potatoes for improved irrigation management." Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-07192007-134318.
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Moreira, LuÃs ClÃnio JÃrio. "Estimating irrigated watermelon evapotranspiration using sebal, soil-water balance and eddy correlations." Universidade Federal do CearÃ, 2009. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=5217.
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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgicoIn applications of the SEBAL (Surface Energy Balance Algorithm for Land) algorithm parameters for physical processes adjusted for other regions of the planet are commonly used. Therefore, there is a need for validation of the estimates made with the algorithm compared with other conventional methods of estimating evapotranspiration. Thus, this study main goal was to evaluate the satellite-based algorithm to estimate evapotranspiration of irrigated watermelon using as comparative methods: soil water balance and eddy correlation. The studied area was a plot of 1 ha located in the irrigated district of the low Acaraà River. Foliar coverage was obtained from digital images taken from a camera. Sensors were installed from the soil surface to a height of 1.5 m for monitoring the temperature in the air. The unsaturated hydraulic conductivity function of the soil was obtained using the instantaneous profile method. The water balance in the soil was done on days 17, 18 and 19 December, 2008, in the 0 to 30 cm depth using soil moisture capacitive sensors. To evaluate the components of net radiation and evapotranspiration using the method of eddy correlation, a micrometeorological tower was installed in the center of the studied area, where latent heat flux (LE), sensible heat flux (H) and evapotranspiration were determined. With climate data from a meteorological station nearby and using the FAOÂs methodology, net radiation (Rn) and soil heat flow (G) were determined. The SEBAL algorithm was applied in two Landsat5 satellite images acquired in 17/12/2008 and 02/01/2009 for estimating the net radiation and daily evapotranspiration. The measured temperature at the soil surface and in the air at 10 cm high was over 40  C near noon time. The unsaturated hydraulic conductivity function found was of the form K (θ) = 0.089 e28, 53θ and K (θ) = 0.0469 e48, 773θ, respectively for 0 - 15 and 15 - 30 cm. The evapotranspiration obtained from soil water balance with capacitive sensors in the study period was 9.37; 12.18 and 11.27 mm day-1, respectively in 17; 18 and December 19, 2008. For the radiation balance it was found that the latent heat flux was underestimated by using the method of eddy correlation with maximum values of the order of 150 W m-2. The sensible heat flux was always larger than the LE during the day, with maximum values near 300 W m-2. The energy balance done but accounting H + LE and Rn â G produced a residual error of around 60%. The daily average values of ETc (eddy correlations) for part of the experimental period were in the range of 0.91 to 1.18 mm day-1, with an average of 0.96 mm day-1. The satellite image that was applied to SEBAL algorithm presented many clouds, affecting the estimation of the components of radiation balance and evapotranspiration. In the area of watermelon, SEBAL estimates of evapotranspiration for dates 17/12/2008 and 02/01/2009 were 6.5 and 4.0 mm day-1, respectively. For validation, the ETo obtained by Penman-Montheith method at the time of satellite overpass was 0.53 mm h-1, while Etc obtained with SEBAL, eddy correlation and soil-water balance was 0.78; 0.11 and 0.55 mm h-1, respectively.
Nas aplicaÃÃes feitas com o SEBAL (Surface Energy Balance Algorithm for Land), estÃo sendo utilizadas parametrizaÃÃes de processos fÃsicos ajustados para outras regiÃes do planeta. Portanto, existe uma necessidade de validaÃÃo das estimativas feitas com o algoritmo comparando com outros mÃtodos usuais de estimativa de evapotranspiraÃÃo. Assim, esse trabalho teve como objetivo avaliar o algoritmo SEBAL na estimativa da evapotranspiraÃÃo da melancia irrigada usando como mÃtodos comparativos o balanÃo hÃdrico no solo e mÃtodo das correlaÃÃes turbulentas (eddy correlation). A Ãrea estudada foi um lote de 1 ha localizado no PerÃmetro Irrigado Baixo AcaraÃ. A cobertura Foliar foi obtida a partir de fotografias digitais. Foram instalados sensores a partir da superfÃcie do solo atà a altura de 1,5 m para monitoramento da temperatura no ar. Para fazer o balanÃo hÃdrico no solo foi encontrada a funÃÃo da condutividade hidrÃulica nÃo saturada atravÃs da metodologia do perfil instantÃneo. O balanÃo hÃdrico no solo foi feito nos dias 17, 18 e 19/12/2008 na camada de 0 a 30 cm usando sensores capacitivos de umidade. Para avaliar os componentes do balanÃo de radiaÃÃo e a evapotranspiraÃÃo atravÃs do mÃtodo das correlaÃÃes turbulentas foi instalada uma torre micrometeorolÃgica no centro da Ãrea, onde o fluxo de calor latente (LE), o fluxo de calor sensÃvel (H) e a evapotranspiraÃÃo foram determinados. Com dados climÃticos de uma estaÃÃo meteorologia prÃximo a Ãrea e usando a metodologia da FAO foi estimado a radiaÃÃo lÃquida (Rn) e o fluxo de calor no solo (G). O algoritmo SEBAL foi usado nas imagens do TM-Landsat 5 dos dias 17/12/2008 e 02/01/2009 para estimar o balanÃo de radiaÃÃo e a evapotranspiraÃÃo diÃria. A temperatura na superfÃcie e a 10 cm de altura prÃximos ao meio dia foi superior a 40ÂC. A funÃÃo da condutividade hidrÃulica no solo nÃo saturado para camada de 0 â 15 e 15 â 30 cm foi: K(θ) = 0,089e28,53θ e K(θ) = 0,0469e48,773θ, respectivamente. A evapotranspiraÃÃo obtida atravÃs do balanÃo hÃdrico com sensores capacitivos nos dias analisados foi 9,37; 12,18 e 11,27 mm dia-1, respectivamente em 17; 18 e 19 de dezembro de 2008. No balanÃo de energia observou-se que o fluxo de calor latente foi subestimado usando o mÃtodo das correlaÃÃes turbulentas apresentando valores mÃximos no dia nunca superiores a 150 W m-2. O fluxo de calor sensÃvel esteve sempre maior que o LE durante o dia, apresentando valores mÃximos prÃximos a 300 W m-2. O erro de fechamento da equaÃÃo do balanÃo de energia obtido atravÃs do equacionamento entre H + LE e Rn â G foi de cerca de 60%. Os valores mÃdios diÃrios da ETc (correlaÃÃes turbulentas) para parte do perÃodo experimental estiveram na faixa de 0,91 a 1,18 mm dia-1, com mÃdia de 0,96 mm dia-1. As imagens de satÃlites em que foi usado o algoritmo SEBAL apresentaram nuvens comprometendo a estimativa dos componentes do balanÃo de radiaÃÃo e a evapotranspiraÃÃo. Na Ãrea da melancia, a evapotranspiraÃÃo diÃria usando o SEBAL nos dias 17/12/2008 e 02/01/2009 foi 6,5 e 4,0 mm dia-1, respectivamente. Na anÃlise comparativa, a ETo na hora da passagem do satÃlite foi de 0,53 mm h-1, enquanto a ETc foi de 0,78; 0,11 e 0,55 mm h-1 estimada com o SEBAL, mÃtodos das correlaÃÃes turbulentas e balanÃo hÃdrico, espectivamente.
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Pinto, Victor Meriguetti. "Simulation of water and nitrogen dynamics in a Cerrado soil under coffee cultivation using SWAP and ANIMO models." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/64/64134/tde-02022016-105753/.
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Agriculture when only focused on production leads to an unsustainable use of inputs with negative consequences to the environment and human health. One consequence of the excessive use of fertilizers is the pollution of surface and underground water resources in agricultural eco-systems and their boundaries. The Brazilian Cerrado has been suffering the transformations of the intensive agriculture during the last decades. Due to the poor fertility of soils, in general very sandy and of low pH, the use of agricultural inputs is intensified and the nutrient downward transport by leaching becomes a serious problem in different regions. Information about the current use practices of fertilizer use in the Cerrado environment must be gathered for a healthy transition of this biome. Models based on physical and chemical processes are useful tools to simulate water and nutrient dynamics in agricultural systems, including the related losses due to adopted managements. They have the potential to evaluate different scenarios to predict outcomings of such practices. Among the available models for such processes, SWAP (Soil, Water, Atmosphere and Plant model) has been used under several agronomic conditions to describe hydrologic processes, and ANIMO (Nitrogen in Agriculture model) to simulate N cycling in agricultural systems. Our study presents an application of SWAP to adult perennial coffee crops along one productive cycle, with focus on deep drainage losses and irrigation management in a representative Brazilian Cerrado management system. The SWAP/ANIMO combination was used in this study to simulate N absorption by coffee plants and N leaching in the form NO3-N, as a result of an intensive fertilizer management practice. The ANIMO program was calibrated in relation to one N treatment, of 400 kg ha-1 year-1, and was evaluated with independent data of NO3-N in soil solution of another treatment of 800 kg ha-1 year-1. The yearly water balance (WB) obtained from SWAP was similar to that obtained through a sequential climatologic WB of Thornthwaite and Matter. However, the monthly deep drainage values obtained by SWAP as compared to the WB values presented differences with a determination coefficient of 0.77 in a linearization of the results. Irrigation scenarios with intervals of 3(IF3), 5(IF5), 10 (IF10) e 15 (IF15) days between water applications were simulated by SWAP and compared with the irrigation management practiced in the farm where the experiment was carried out. These simulations showed for longer intervals (IF15) drainage losses were smaller, water productivity higher, as well as relative productivity. Measurements of N absorption by plants obtained experimentally were similar to ANIMO simulations. Sensitivity analyses of the model showed that leaching and soil solution concentration of NO3-N are sensitive to soil pH and temperature of the decomposition processes. We conclude that the combination of SWAP with ANIMO was efficient for the description of the N cycle in a Cerrado soil-plant-atmosphere systemA agricultura focada apenas na produção leva ao uso insustentável de recursos resultando em consequências negativas para o meio ambiente e a saúde humana. Uma consequência do uso excessivo de fertilizantes é a contaminação dos recursos hídricos subterrâneos e superficiais em ecossistemas agrícolas e nos seus arredores. Devido o solo da região do Cerrado ser pobre em nutrientes, predominantemente arenoso e com alta acidez, o uso de insumos agrícolas é intensificado e o transporte químico de nutrientes via lixiviação é um problema para a agricultura intensiva nas diferentes regiões. Informações sobre as atuais práticas de uso de fertilizantes e seus efeitos no ambiente de Cerrado precisam ser coletadas para reduzir os impactos da agricultura nesse ecossistema. Modelos baseados em processos físicos e químicos são ferramentas úteis para simular a dinâmica da água e nutrientes no meio agrícola e as perdas associadas aos manejos adotados, com potencial para avaliar diferentes cenários de previsão dos resultados dessas práticas. Entre os modelos baseados em processos, o SWAP (modelo Solo, Água, Atmosfera e Planta) tem sido utilizado com sucesso em várias condições agronômicas para descrever processos hídricos, e o ANIMO (modelo de nitrogênio na agricultura) para simular o ciclo do nitrogênio em sistemas agrícolas. Nosso estudo apresenta uma aplicação do SWAP para culturas de café perenes maduras ao longo de um ciclo produtivo, com foco nas perdas por drenagem e no manejo da irrigação em um sistema típico do Cerrado Brasileiro. A combinação dos modelos SWAP/ANIMO foi utilizada nesse estudo para simular a absorção de N pelas plantas de café e a lixiviação do nitrogênio na forma de nitrato (NO3-N) resultante de uma prática de manejo de fertilizantes intensiva. O ANIMO foi calibrado para o cenário correspondente à aplicação de 400 kg ha-1 ano-1 de fertilizante mineral, e foi avaliado com dados independentes de NO3-N na solução do solo medidos em parcelas de outro tratamento que receberam 800 kg ha-1 ano-1. O balanço hídrico anual obtido pelo SWAP foi semelhante ao obtido pelo balanço sequencial climatológico, de Thornthwaite e Matter. No entanto, os valores mensais de drenagem profunda obtidos pelo SWAP e comparados com os resultados do balanço climatológico apresentaram diferenças, com um coeficiente de determinação de 0,77 na linearização dos resultados. Cenários de irrigação com intervalos de 3 (IF3), 5 (IF5), 10 (IF10) e 15 (IF15) dias entre aplicações de água foram simulados utilizando o SWAP e comparados com a prática de manejo da fazenda onde o estudo experimental foi realizado. As simulações dos cenários com o SWAP mostraram que as irrigações com intervalos mais longos (IF15) apresentam menores quantidades de perdas por drenagem, maior produtividade da água e produtividade relativa da cultura. As medidas de absorção de N pelas plantas obtidas experimentalmente foram similares às estimativas do modelo ANIMO. As analises de sensibilidade do modelo mostraram que as previsões da lixiviação e concentração de NO3-N na solução do solo são sensíveis às variáveis pH do solo e temperatura de referência dos processos de decomposição. Conclui-se que a combinação dos modelos unidimensionais baseados em processos SWAP/ANIMO foi eficaz na descrição do ciclo do N avaliado no sistema solo-planta do Cerrado
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Abebe, Yibekal Alemayehu. "Managing the soil water balance of hot pepper (Capsicum annuum L.) to improve water productivity." Thesis, University of Pretoria, 2010. http://hdl.handle.net/2263/25257.
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A series of field, rainshelter, growth cabinet and modelling studies were conducted to investigate hot pepper response to different irrigation regimes and row spacings; to generate crop-specific model parameters; and to calibrate and validate the Soil Water Balance (SWB) model. Soil, climate and management data of five hot pepper growing regions of Ethiopia were identified to develop irrigation calendars and estimate water requirements of hot pepper under different growing conditions. High irrigation regimes increased fresh and dry fruit yield, fruit number, harvest index and top dry matter production. Yield loss could be prevented by irrigating at 20-25% depletion of plant available water, confirming the sensitivity of the crop to mild soil water stress. High plant density markedly increased fresh and dry fruit yield, water-use efficiency and dry matter production. Average fruit mass, succulence and specific leaf area were neither affected by row spacing nor by irrigation regimes. There were marked differences among the cultivars in fruit yields despite comparable top dry mass production. Average dry fruit mass, fruit number per plant and succulence were significantly affected by cultivar differences. The absence of interaction effects among cultivar and irrigation regimes, cultivars and row spacing, and irrigation regimes and row spacing for most parameters suggest that appropriate irrigation regimes and row spacing that maximize productivity of hot pepper can be devised across cultivars. To facilitate irrigation scheduling, a simple canopy cover based procedure was used to determine FAO-type crop factors and growth periods for different growth stages of five hot pepper cultivars. Growth analysis was done to calculate crop-specific model parameters for the SWB model and the model was successfully calibrated and validated for five hot pepper cultivars under different irrigation regimes or row spacings. FAO basal crop coefficients (Kcb) and crop-specific model parameters for new hot pepper cultivars can now be estimated from the database, using canopy characteristics, day degrees to maturity and dry matter production. Growth cabinet studies were used to determine cardinal temperatures, namely the base, optimum and cut-off temperatures for various developmental stages. Hot pepper cultivars were observed to require different cardinal temperatures for various developmental stages. Data on thermal time requirement for flowering and maturity between plants in growth cabinet and open field experiments matched closely. Simulated water requirements for hot pepper cultivar Mareko Fana production ranged between 517 mm at Melkassa and 775 mm at Alemaya. The simulated irrigation interval ranged between 9 days at Alemaya and 6 days at Bako, and the average irrigation amount per irrigation ranged between 27.9 mm at Bako and 35.0 mm at Zeway.Thesis (PhD)--University of Pretoria, 2010.
Plant Production and Soil Science
unrestricted
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Pinheiro, Everton Alves Rodrigues. "Hydrological modeling of soil-water availability in the Caatinga biome." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/11/11152/tde-10112016-170843/.
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Northeastern Brazil is hydrologically characterized by recurrent droughts leading to a highly vulnerable natural water resource system. The region contains the Caatinga biome, a sparsely studied ecosystem, covering an area of approximately 800,000 km2. Reduced wateravailability is projected to take place in large regions of the globe, including Northeastern Brazil. Given the strong interactions between climate and vegetation, research has addressed climate change effects on natural and agricultural ecosystems. In this context, soil hydraulic properties are essential to assess soil water flow, and thus the ability of soil to supply water to plants at potential rates under different ranges of pressure head. Based on that, the aims of this thesis are: to increase insight in water balance components for the Caatinga biome, under current and future climate scenarios; and to assess the ability of soils in supplying water to plants by the further development of an existing matric flux potential approach, followed by its application to a group of soils from two Brazilian climatic zones (semi-arid and subhumid). Both for current and future climate scenarios, hydrological simulations were performed with SWAP model parameterized for a preserved Caatinga basin of 12 km2. The validation of the simulations was performed using a dataset of daily soil-water content measurements taken at 0.2 m depth in the period from 2004 to 2012. The soil water supplying capacity was evaluated through a multilayer matric flux potential approach, coupling the soil hydraulic properties, root length density and plant transpiration. Regarding the current climate conditions, the Caatinga biome returns 75% of the annual precipitation to the atmosphere, whereas the partitioning of total evapotranspiration into its components (transpiration, evaporation and interception) on annual basis accounts for 41%, 40% and 19%, respectively. Evapotranspiration and air temperature are most sensitive to soil moisture during the periods June-September and December-January. Concerning the future climate, transpiration was enhanced by 36%, soil evaporation and interception losses reduced by 16% and 34%, respectively. The amount of precipitation returned to the atmosphere was on average 98%. For both climate scenarios, the soil-plant-atmosphere fluxes seem to be controlled by the surface soil layer (0-0.2 m) which provides, on average, 80% of the total transpiration, suggesting that the Caatinga biome may become completely soil-water pulse dominated under scenarios of reduced water availability. The matric flux potential analysis revealed that soils from the semiarid zone were able to deliver water to plants at potential rates under a wider range of bulk soil pressure head (-36 to -148 m), whereas the soils from the wetter zone showed more hydraulic restriction with limiting soil water potential above -1.5 m. For the analyzed soils, only a negligible increase in available water results from decreasing the root water potential below -150 m, therefore, in order to adapt to water-limited conditions, plant species may invest in other adaptive strategies, rather than spending energy in structures that allow a reduction of the lower suction limit in their tissues.O Nordeste do Brasil é hidrologicamente caracterizado por secas recorrentes, tornando os recursos hídricos naturais altamente vulneráveis. Nesta região está o bioma Caatinga, ocupando uma área de aproximadamente 800.000 km2. Cenários de déficit hídrico são projetados para grandes regiões do globo, incluindo o Nordeste brasileiro. Devido às interações entre clima e vegetação, várias pesquisas têm abordado os efeitos das mudanças climáticas sobre os ecossistemas naturais e agrícolas. Neste contexto, as propriedades hidráulicas do solo são essenciais para avaliar o movimento de água, e assim a capacidade de fornecimento de água às plantas. Com base nesta contextualização, os objetivos desta tese são: simular os componentes do balanço hídrico do bioma Caatinga para cenários climáticos atuais e futuros; e avaliar a capacidade de alguns solos em fornecer água às plantas a partir de uma abordagem de potencial de fluxo matricial. Para os cenários climáticos atuais e futuros, simulações hidrológicas foram realizadas com o modelo SWAP, parametrizado para uma microbacia de 12 km2, inserida em área de Caatinga preservada. A validação das simulações foi processada a partir de medidas diárias do conteúdo de água do solo na profundidade de 0,2 m no período de 2004 a 2012. A capacidade do solo em fornecer água às plantas foi avaliada através da atualização de uma função de potencial de fluxo matricial, que acopla as propriedades hidráulicas do solo, densidade de comprimento radicular e transpiração das plantas, aplicada a um grupo de solos da zona climática semiárida e sub-úmida. Como resultados principais destacam-se: nas condições climáticas atuais, o bioma Caatinga retorna 75% da precipitação anual para a atmosfera como evapotranspiração, particionada entre seus componentes (transpiração, evaporação e intercepção) em 41%, 40% e 19%, respectivamente. Evapotranspiração e temperatura do ar foram sensíveis à umidade do solo durante os períodos de junho-setembro e dezembro-janeiro. Em relação ao cenário climático futuro, a taxa de transpiração foi acrescida em 36%. A evaporação do solo e a interceptação foram reduzidas em 16% e 34%, respectivamente. A quantidade de precipitação devolvida para a atmosfera foi em média 98%. Para ambos os cenários climáticos, é sugerido que os fluxos de água no sistema solo-planta-atmosfera são controlados pela camada superior do solo (0-0,2 m), fornecendo, em média, 80% do total transpirado, indicando que, caso os cenários de disponibilidade hídrica reduzida se confirmem, o bioma Caatinga pode se tornar completamente dependente dos pulsos de água no solo. A partir do potencial de fluxo matricial limitante revelou-se que os solos da região semiárida são capazes de manter o fluxo de água às plantas em taxas potenciais em condições de solo seco (potencial matricial limitante variando de -36 a -148 m), enquanto que, os solos da região mais úmida indicaram severa restrição hidráulica, com potencial matricial limitante maior do que -1,5 m. Ainda para os solos analisados, a atribuição de potencial na superfície da raiz inferior a -150 m não ocasionou aumento de disponibilidade hídrica, indicando que valores menores que -150 m não implicam em uma estratégia viável para suportar baixa disponibilidade hídrica.
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Tesfamariam, Eyob Habte. "Modelling the soil water balance of canola Brassica napus L (Hyola 60)." Diss., Pretoria : [s.n.], 2004. http://upetd.up.ac.za/thesis/available/etd-09212004-082030.
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Zhang, Shulan. "Soil hydraulic properties and water balance under various soil management regimes on the Loess Plateau, China /." Umeå : Dept. of Forest Ecology, Swedish University of Agricultural Sciences, 2005. http://epsilon.slu.se/2005126.pdf.
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Gärdenäs, Annemieke. "Soil organic matter in forest soils : effects of climate and water balance /." Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1998. http://epsilon.slu.se/avh/1998/91-576-5530-8.gif.
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Thadei, Simon Yuda. "Evaluation of effective rainfall by a physically-based soil-water balance model." Thesis, University of Newcastle Upon Tyne, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316263.
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Gustafsson, David. "Boreal land surface water and heat balance : Modelling soil-snow-vegetation-atmosphere behaviour." Doctoral thesis, KTH, Mark- och vattenteknik, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3406.
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The water and heat exchange in thesoil-snow-vegetation-atmosphere system was studied in order toimprove the quantitative knowledge of land surface processes.In this study, numerical simulation models and availabledatasets representing arable land, sub-alpine snowpack, andboreal forest were evaluated at both diurnal and seasonaltimescales. Surface heat fluxes, snow depth, soil temperatures andmeteorological conditions were measured at an agriculturalfield in central Sweden during three winters and two summersfrom 1997 to 2000 within the WINTEX project. A one-dimensionalsimulation model (COUP) was used to simulate the water and heatbalance of the field. Comparison of simulated and measured heatfluxes in winter showed that parameter values governing theupper boundary condition were more important for explainingmeasured fluxes than the formulation of the internal mass andheat balance of the snow cover. The assumption of steady stateheat exchange between the surface and the reference height wasinadequate during stable atmospheric conditions. Independentestimates of the soil heat and water balance together with thecomparison of simulated and measured surface heat fluxes showedthat the eddy-correlation estimates of latent heat fluxes fromthe arable field were on average 40 % too low. The ability of a multi-layered snowpack model (SNTHERM) tosimulate the layered nature of a sub-alpine snowpack wasevaluated based on a dataset from Switzerland. The modelsimulated the seasonal development of snow depth and densitywith high accuracy. However, the models ability to reproducethe strong observed snowpack layering was limited by theneglection of the effect of snow microstructure on snowsettling, and a poor representation of water redistributionwithin the snowpack. The representation of boreal forest in the land surfacescheme used within a weather forecast (ECMWF) model was testedwith a three-year dataset from the NOPEX forest site in centralSweden. The new formulation with separate energy balances forvegetation and the soil/snow beneath the tree cover improvedthe simulation of seasonal and diurnal variations in latent andsensible heat flux. Further improvements of simulated latentheat fluxes were obtained when seasonal variation in vegetationproperties was introduced. Application of the COUP model withthe same dataset showed that simulation of evaporation fromintercepted snow contributed to a better agreement with themeasured sensible heat flux above forests, but also indicatedthat the measurements might have underestimated latent heatflux. The winter sensible heat flux above the forest wasfurther improved if an upper limit of the aerodynamicresistance of 500 s m-1 was applied for stable conditions. A comparison of the water and heat balance of arable landand forest confirmed the general knowledge of the differencesbetween these two surface types. The forest contributed withconsiderably more sensible heat flux to the atmosphere than thearable land in spring and summer due to the lower albedo andrelatively less latent heat flux. Latent heat flux from theforest was higher in winter due to the evaporation ofintercepted snow and rain. The net radiation absorbed by theforest was 60 % higher than that absorbed by the arable land,due to the lower surface albedo in winter. Key words:soil; snow; land surface heat exchange;forest; arable land; eddy-correlation.QC 20100614
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Eilers, V. H. M. "The estimation of groundwater recharge by soil water balance in semi-arid regions." Thesis, Cranfield University, 2002. http://dspace.lib.cranfield.ac.uk/handle/1826/4215.
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Quantification of groundwater recharge is a crucial prerequisite for sustainable groundwater resource management, particularly in semi-arid areas where there are large demands for groundwater supplies. This research presents an alternative approach for recharge estimation based on the soil water balance technique. The purpose is to develop a model which provides a suitable balance between physical credibility and data which realistically can be gathered. A spreadsheet model was written based on the conceptual representation of the principal physical processes which actually affect recharge in a semi-arid area. Alternative procedures were included in order to represent: (a) the estimation of runoff, (b) the inclusion of the period with predominant bare soil evaporation and (c) the accounting for evapotranspiration following rainfall on dry soil. The model was tested using real data from a semi-arid region (Northeast Nigeria) making use of selected periods of days and years in order to illustrate the principal model characteristics. The results were presented in the form of diagrams and graphs helping to visualise the interactions between the physical components and the effect of the additional procedures on recharge estimation. The credibility of the model was investigated using an alternative concept of 'analysis of plausibility'. This concept makes use of as wide as possible a range of quantitative and qualitative information from the hydrological system in order to verify the robustness of the model when extensive datasets required by conventional validation techniques are not available. The results suggested that the modelled recharge is physically sound and it is in line with the overall determination of recharge in semi-arid areas by a range of methods. The soil water balance model was utilised to explore important aspects of recharge in semi-arid regions showing the effect of the field variability on the model's output. The preliminary results show that the developed concept reasonably represents the inherent field variability, thus corroborating the strength of the approach for recharge estimation in semi-arid regions.
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Rim, Chang-Soo. "Daily estimation of local evapotranspiration using energy and water balance approaches." Diss., The University of Arizona, 1995. http://hdl.handle.net/10150/191190.
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Meteorological and environmental (i.e. soil water content) data measured from semiarid watersheds (Lucky Hills and Kendall) during the summer rainy and winter periods were used to study the interrelationships between variables, and to evaluate the effects of variables on the daily estimation of actual evapotranspiration (AET). The relationship between AET and potential evapotranspiration (PET) as a function of an environmental factor was the major consideration of this research. The relationship between AET and PET as a function of soil water content as suggested by Thornthwaite-Mather, Morton and Priestley-Taylor was studied to determine its applicability to the study area. Furthermore, multiple linear regression (MLR) analysis was employed to evaluate the order of importance of the meteorological and soil water factors involved. Finally, the information gained was used for MLR model development. The results of MLR analysis showed that the combined effects of available energy, soil water content and wind speed were responsible for 77 % of the observed variations in AET at Lucky Hills watershed and 70 % at Kendall watershed during the summer rainy period. The analyses also indicated that the combined effects of available energy, vapor pressure deficit and wind speed were responsible for 70 % of the observed variations in AET at Lucky Hills watershed and 72 % at Kendall watershed during the winter period. However, the test results of three different approaches, using the relationships between AET and PET as a function of soil water content indicated some inadequacy. The low correlation between PET, AET, and soil moisture conditions raised some doubt concerning the validity of methods developed elsewhere, and indicated the effects of energy availability on the relationship between PET, AET, and soil water content regardless of the soil water condition. In contrast, agreement between observed AET and estimated AET from MLR models during the summer rainy and winter periods at both watersheds indicated that MLR models can give reasonable estimates of AET, at least under the climatic conditions in which the formulae were developed.
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Pollacco, Joseph. "Inverse methods to determine parameters in a physically based model of soil water balance." Thesis, University of Newcastle Upon Tyne, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413964.
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Hakamada, Rodrigo Eiji. "Physiological responses and soil water balance of clonal Eucalyptus under contrasting spacings and genotypes." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/11/11150/tde-28112016-113417/.
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Planting density and genotype have close relationship with the water relations in plants. The scenario of increased occurrence of extreme weather events and the change of Eucalyptus forest plantations to high water deficit regions, led us to the three key questions of this study: (1) What is the relationship between planting density and the potential water stress? (2) The planting spacing interferes the water use efficiency (WUE), i.e. the amount of biomass produced by the amount of water transpired? (3) Can the planting density change the soil water balance (BHS)? To develop this work, we settled a field trial in Mogi Guacu, SP, in February 2012. We planted four genetic material (Eucalyptus grandis x E.urophylla1 {Urograndis1}, Eucalyptus grandis x E.urophylla2, E.urophylla and E.grandis x E.camaldulensis {Grancam}) with different levels of tolerance to drought and four planting spacings (3.4, 7.0, 10.5 and 16.9 m2 plant-1, which correspond to densities of 2,949 , 1,424 and 1,028 and 591 plants ha-1). In Chapter 1, we evaluated the leaf water potential (representing potential water stress) of the four clones for 1 year, between 1.5 and 2.5 years. Regardless of the genetic material, the higher the wood productivity, the greater the leaf water potential. The denser planting (2,949 plants ha-1) stands generated 39% more wood, however, water stress potential reached up to 33% higher than the least dense planting (591 plants ha-1). In the second chapter, during the same period, we evaluated the efficiency of water use, which did not vary according to the change of planting density, but showed differences between genotypes with US 2.3, 2.2 and 1, 5 g L-1 to Urograndis, Urophylla and Grancam, respectively, at a density of 1,424 plants ha-1. Finally, the third chapter evaluated for two years, between 1.7 and 3.7 years, transpiration (T), soil evaporation (Es) and canopy interception (Ei), which together made up evapotranspiration (ET). Subtraction of precipitation (P) per ET resulted in soil water balance (SWB). The SWB was positive or near zero for the two clones evaluated (Urograndis1 and Grancam) when planting density was less than or equal to 1,028 trees ha-1. In the denser planting, the balance was -25%. These studies show that: a higher wood growth results in a higher potential drought stress, generating a clear trade-off between production and survival of trees. However, the detailed study of genetic materials fall under that there are increasing opportunities in water use efficiency, though without the increase in water use, bringing a greater share of water in the watershed scale. Finally, plantations above 1,028 ha-1 trees resulted in a negative soil water balance of -25% at the peak of growth. Together, this study reveals that spacing associated with genotypes can serve as tools in the search for balance between timber production and conservation of natural resources.A densidade de plantio e o genótipo possuem estreita relação com as relações hídricas nas plantas. Sob um cenário de maior ocorrência de eventos climáticos extremos e do avanço dos plantios florestais de eucalipto para regiões de elevado déficit hídrico, elaboramos três perguntas-chave para esse estudo: (1) Qual a relação entre a densidade de plantio e o potencial estresse hídrico? (2) O espaçamento de plantio interfere na eficiência do uso da água (EUA), i.e., na quantidade de biomassa produzida pela quantidade de água transpirada? (3) Pode a densidade de plantio alterar o balanço hídrico do solo (BHS)? Para responder a essas questões, instalou-se um ensaio de campo em Mogi Guacu, SP, em fevereiro de 2012. Foram plantados quatro materiais genéticos (Eucalyptus grandis x E.urophylla1 {Urograndis1}, Eucalyptus grandis x E.urophylla2, E.urophylla e E.grandis x E.camaldulensis {Grancam}) com distintos níveis de tolerância à seca e quatro espaçamentos de plantio (3,4, 7,0, 10,5 e 16,9 m2 planta-1, que correspondem às densidades de 2.949, 1.424 e 1.028 e 591 plantas ha-1). No capítulo 1, avaliou-se o potencial hídrico foliar (representando o potencial estresse hídrico) dos quatro clones durante 1 ano, entre 1,5 e 2,5 anos. Independentemente do material genético, quanto maior a produtividade madeireira atingida, maior o potencial hídrico foliar. Os plantios mais adensados (2.949 plantas ha-1) geraram povoamentos 39% mais produtivos, no entanto, o potencial estresse hídrico chegou a atingir 33% acima do plantio menos adensado (591 plantas ha-1). No segundo capítulo, durante o mesmo período, avaliou-se a eficiência do uso da água, que não variou conforme a mudança de densidade de plantio, mas apresentou diferença entre os genótipos, com EUA de 2,3, 2,2 e 1,5 g L-1 para os clones Urograndis, Urophylla e Grancam, respectivamente, na densidade de 1.424 plantas ha-1. Por fim, o terceiro capítulo avaliou durante dois anos, entre 1,7 e 3,7 anos, a transpiração (T), evaporação do solo (Es) e interceptação de água pela copa (Ei), que somados compunham e evapotranspiração (ET). A subtração da precipitação (P) da ET resultou no balanço hídrico do solo (BHS). O BHS foi positivo ou próximo de zero para os dois clones avaliados (Urograndis1 e Grancam) quando a densidade de plantio foi inferior ou igual a 1.028 árvores ha-1. No plantio mais adensado, o balanço foi de -25%. Estes estudos demonstram que: a maior produtividade madeireira acarreta em maior potencial estresse hídrico, gerando um claro dilema entre a produção e a sobrevivência dos plantios. No entanto, o estudo detalhado dos materiais genéticos releva que há possibilidades de incremento na eficiência do uso da água sem que ocorra o aumento no uso da água, trazendo um maior compartilhamento da água na escala da microbacia. Por fim, plantios acima de 1.028 árvores ha-1 resultaram em um balanço hídrico do solo negativo médio de -25% no pico do crescimento. Em conjunto, o presente trabalho releva que o espaçamento associado a materiais genéticos específicos, podem servir como ferramenta na busca pelo equilíbrio entre a produção madeireira e a conservação de recursos naturais.
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Junior, Paulo Ponce Arroio. "Aprimoramento das rotinas e parâmetros dos processos hidrológicos do modelo computacional Soil and Water Assessment Tool - SWAT." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/18/18139/tde-25052017-084925/.
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O modelo Soil and Water Assessment Tool (SWAT) tem sido utilizado para avaliar os impactos do uso e manejo da terra nos recursos hídricos, sedimentos e agroquímicos em diversas escalas e condições ambientais em todo o mundo. Entretanto, pelo fato de ter sido desenvolvido em centros de pesquisa norte-americanos, alguns parâmetros e rotinas de simulação não refletem adequadamente determinados processos de bacias localizadas em regiões tropicais. Nesse sentido, o presente trabalho visou aprimorar a modelagem hidrológica do SWAT através da revisão e modificação de processos relacionados à simulação da evapotranspiração. Os procedimentos propostos incluíram a alteração das rotinas de dormência vegetal no código fonte do modelo e a modificação dos cronogramas de operações de manejo e parâmetros do banco de dados de crescimento das plantas, visando reproduzir com maior precisão o ciclo das culturas em bacias tropicais. As modificações foram testadas em cinco bacias localizadas no Estado de São Paulo, com áreas entre 42 e 5.959 km², sendo comparados os resultados obtidos antes e depois da implementação das mesmas. Com as alterações, a análise do balanço hídrico anual evidenciou um aumento nos valores de evapotranspiração de cerca de 61% nas bacias, aproximando-se dos totais anuais de evapotranspiração calculados através de métodos empíricos, bem como houve redução significativa do escoamento superficial. Verificou-se uma melhoria da simulação de vazão em todas as bacias, sendo obtidos valores superiores para o Coeficiente de Eficiência de Nash-Sutcliffe (NSE) quando comparados à simulação sem as alterações. A calibração e validação foram realizadas com base na simulação modificada, sendo obtidos valores de NSE mensais entre 0,71 e 0,93 na calibração e 0,53 e 0,88 na validação, enquanto os valores diários de NSE situaram-se entre 0,51 e 0,82 na calibração e 0,38 e 0,83 na validação. A calibração a partir de uma simulação na qual as distorções dos processos hidrológicos da bacia estivessem previamente minimizadas resultou em bons resultados sem alteração excessiva dos parâmetros, indicando uma simulação hidrológica de melhor consistência.The Soil and Water Assessment Tool (SWAT) has been used to predict the impact of land management practices on water, sediment, and agricultural chemical yields in a wide range of scales and environmental conditions across the globe. However, originally developed in the United States, some parameters and routines are unrealistic for simulating in tropical watersheds. In this sense, this work aims to improve the hydrologic modeling of SWAT model by reviewing and modifying parameters and routines related to evapotranspiration process. In order to adequately represent crop growth in tropical basins, the proposed procedures included changes in dormancy routines of SWAT source code and modifications of scheduled management operations and plant growth database parameters. These modifications were tested in five different basins at São Paulo State, Brazil, with areas ranging from 42 to 5959 km², by comparing the results before and after their implementation. Annual water balance analysis showed an increase in evapotranspiration about 61% for basins, approaching the total annual evapotranspiration estimated by empirical methods. Hence, it was observed that surface runoff and base flow components showed a decrease. The modifications resulted in improved flow simulation for all basins, showing better Nash-Sutcliffe Efficiency Coefficient (NSE) values compared to the unchanged simulation. Calibration and validation processes used the modified simulation database, being achieved monthly NSE between 0.71 – 0.73 at calibration and 0.53 – 0.88 at validation, while daily NSE were 0.51 – 0.82 at calibration and 0.38 – 0.83 at validation. Overall, minimizing distortions in hydrological processes at pre-calibration step resulted in good estimations without excessive modification of parameters at calibration, attesting a consistent hydrological modeling for the basins analyzed.
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HAMED, LAMY MAMDOH MOHAMED. "NITROGEN BALANCE IN SOIL PROFILE AS AFFECTED BY DIFFERENT SOIL TYPE, SOIL WATER REGIMES, NITROGEN RATE AND APPLICATION METHODS USING 15N TRACER TECHNIQUE." Doctoral thesis, Università degli Studi di Milano, 2014. http://hdl.handle.net/2434/232140.
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The interaction effect of “Soil type, Soil water regime, Nitrogen fertilizer application Rates and Timing” on Nitrogen balancein soil were studied; in terms of nitrogen gained by plant portions, remained in soil, and losses through different ways under wheat (Triticum aestivum L. Giza 168), in order to identify the most proper and effective combinations of above-studied variables that provides a satisfactory grain wheat yield and minimizes the use of chemical nitrogen fertilizers, to save the surrounding environment and to achieve good water saving.
Two fields of experiments were carried out during November and December –April 2012-13, under Egyptian conditionsrepresents two different textured soils, i.e clay located at (30o 16- N latitude, 30o 56- E longitude), and sand soils located at (30o 24- N latitude, 31o 35- E longitude) as growth media of wheat crop. The application methods of Nitrogen rates, 100, 80 and 60% of recommended rates (Clay, 178 kg N & Sand, 238 kg N), were applied as Mode A, 25% at seedling, 25% and tillering, 50% at jointing AND Mode B, 35% at seedling, 65% at tillering.
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Möller, Jason John. "The use of remote sensing for soil moisture estimation using downscaling and soil water balance modelling in Malmesbury and the Riebeek Valley." Thesis, University of the Western Cape, 2014. http://hdl.handle.net/11394/4105.
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>Magister Scientiae - MScSoil moisture forms an integral part of the hydrological cycle and exerts considerable influence on hydrological processes at or near the earth’s surface. Knowledge of soil moisture is important for planning and decision-making in the agricultural sector, land and water conservation and flood warning. Point measurements of soil moisture, although highly accurate, are time consuming, costly and do not provide an accurate indication of the soil moisture variation over time and space as soil moisture has a high degree of spatial and temporal variability. The spatial variability of soil moisture is due to the heterogeneity of soil water holding properties, the influence of plants, and land uses. The downscaling of satellite microwave soil moisture estimates and soil water balance modelling was investigated at six transects in the semi-arid, Western Cape Province of South Africa, as alternatives to in situ soil measurements. It was found that microwave soil moisture estimates compared well to in situ measurements at the six transects (study sites), with coefficient of determination (r2) values greater than 0.7 and root mean square error (RMSE) values less than 1.5%. Downscaling using the universal triangle method, performed well at 4 of the 6 transects, with r2 values great than 0.65 and low to moderate RMSE values (0.5-12%). Soil water balance modelling similarly performed well in comparison with in situ measurements at 4 of the transects with regards to r2 values (>0.6) but had moderate to high RMSE (4.5-19%). Poor downscaling results were attributed to fine scale (within 1 km) surface heterogeneity while poor model performance was attributed to soil hydrological and rainfall heterogeneity within the study areas.
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Geremew, Eticha Birdo. "Modelling the soil water balance to improve irrigation management of traditional irrigation schemes in Ethiopia." Pretoria : [s.n.], 2008. http://upetd.up.ac.za/thesis/available/etd-05242009-121531.
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Krümmelbein, Julia. "Influence of various grazing intensities on soil stability and water balance of a steppe soil in Inner Mongolia, P.R. China /." Kiel : Inst. für Pflanzenernährung und Bodenkunde, 2007. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=016796677&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Paredes, Paula Cristina Santana. "Modelação água-produção para culturas Mediterânicas visando a produtividade da água na prática da rega." Doctoral thesis, ISA/UL, 2014. http://hdl.handle.net/10400.5/7359.
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Dolling, P. J. "Lucerne (Medicago sativa) productivity and its effect on the water balance in southern Western Australia /." Connect to this title, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0108.
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da, Silva Cerozi Brunno, and Silva Cerozi Brunno da. "Phosphorus Dynamics, Mass Balance and Mineralization in Aquaponics Systems." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/620832.
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This study involves tracing inputs, partitioning, and outputs of phosphorus (P) through an aquaponics system. A mathematical model was developed to describe the dynamics of phosphorus in an aquaponics nutrient solution, and to maximize P use efficiency and minimize P waste. We assessed the influence of pH on the availability and speciation of phosphorus in an aquaponics nutrient solution. By using Visual MINTEQ, a freeware chemical equilibrium model for the calculation of element speciation, solubility equilibria, and sorption for natural waters, it was discovered that high pH values favor the formation of calcium phosphate complexes, decreasing the concentration of free phosphorus in aquaponics nutrient solutions. In addition, the mineralization of organic phosphorus in aquaponics systems was evaluated using treatments with phytase supplementation to fish diets, and incorporation of a microbial inoculant in the aquaponics nutrient solution. Overall, dietary phytase and microorganisms promoted phosphorus mineralization and enhanced phosphorus utilization in aquaponics systems. In the end, we conclude that aquaponics systems can keep the same growth performance and quality of vegetable crops grown in conventional systems when the availability and dynamics of phosphorus are well managed.
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George, Brendan Hugh. "Comparison of techniques for measuring the water content of soil and other porous media." University of Sydney, 1999. http://hdl.handle.net/2123/491.
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The measurement of water in soil on a potential, gravimetric or volumetric basis is considered, with studies concentrating on the measurement of water by dielectric and neutron moderation methods. The ability of the time-domain reflectometry technique to measure water content simultaneously at different spatial locations is an important advantage of the technique. The reported apparent dielectric by the TRASE� time-domain reflectometer and Pyelab time-domain reflectometry systems is sensitive to change in extension cable length. In some soil, e.g. a commercial sand, the response to increasing extension length of extension cable is linear. For other soil a linear response occurs for certain lengths of cable at different moisture contents. A single model accounting for clay content, extension cable length, time-domain reflectometry system, probe type and inherent moisture conditions explained 62.2 % of variation from the control (0 m extension) cable. The extension cable causes a decrease in the returning electromagnetic-wave energy; leading to a decline in the slope used in automatic end-point determination. Calibration for each probe installation when the soil is saturated, and at small water contents is recommended. The ability of time-domain reflectometry, frequency-domain and neutron moderation techniques in measuring soil water content in a Brown Chromosol is examined. An in situ calibration, across a limited range of water contents, for the neutron moderation method is more sensitive to changing soil water content than the factory supplied 'universal' calibration. Comparison of the EnviroSCAN� frequency-domain system and the NMM count ratio indicates the frequency-domain technique is more sensitive to change in soil water conditions. The EnviroSCAN� system is well suited to continuous profile-based measurement of soil water content. Results with the time-domain reflectometry technique were disappointing, indicating the limited applicability of time-domain reflectometry in profile based soil water content measurement in heavy-textured soil, or soil with a large electrical conductivity. The method of auguring to a known depth and placement of the time-domain reflectometry probe into undisturbed soil is not recommended. A time-domain reflectometry system is adapted for in situ measurement of water in an iron ore stockpile. The laboratory calibration for water content of the processed iron ore compares favourably to a field calibration. In the field study, the 28 m extension cable used to connect the probes to the time-domain reflectometry affected the end-point determination of the time-domain reflectometry system. To account for this, 0.197 should be subtracted from the reported apparent dielectric before calculation of volumetric moisture content.
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Larsbo, Mats. "An improved dual-permeability model of solute transport in structured soils : model development and parameter identification in laboratory and field experiments /." Uppsala : Dept. of Soil Sciences, Swedish University of Agricultural Sciences, 2005. http://epsilon.slu.se/200551.pdf.
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Beletse, Yacob Ghebretinsae. "Modelling the soil water and salt balance of planted pastures irrigated with sodium sulphate rich mine effluent." Diss., Pretoria : [s.n.], 2004. http://upetd.up.ac.za/thesis/available/etd-01182005-083427.
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Dolling, Perry. "Lucerne (Medicago sativa) productivity and its effect on the water balance in southern Western Australia." University of Western Australia. Faculty of Natural and Agricultural Sciences, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0108.
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[Truncated abstract] In southern Western Australia the replacement of deep-rooted native vegetation with annual species has resulted in rising water tables and increased salinity due to insufficient water use. The area has a Mediterranean-type climate where rainfall during summer is generally low but variable resulting in limited plant growth. However, if rainfall does occur it potentially can contribute to to the increased water excess or drainage by increasing the soil water content before the main drainage period in winter. The first study investigated factors controlling soil water content changes during the fallow (December to May) in annual farming systems. This was achieved by examining variation in available soil water storage to a depth of 1.0-1.5 m at three sites within 13 seasons. Reasons for the variation were examined using the Agricultural Production Systems Simulator (APSIM). This study also investigated the relationship between soil water content at the end of the fallow period (1 May) and the amount of drainage below 2.5 m by using APSIM coupled to historical weather records at three locations. At the end of the fallow a mean of 24 mm (or 25%) of rainfall during the fallow was retained in the soil. Losses of soil water during the fallow were due to evaporation (mean of 60 mm), transpiration from plant cover (mean of 12 mm) and drainage below the root zone and run off (combined mean of 13 mm). Soil water accumulation during the fallow period had a significant impact on simulated drainage under wheat in the following growing season. Every 1 mm increase in soil wetness at the end of the fallow resulted in a 0.7-1 mm increase in simulated drainage during the growing season. ... Variation in the water excess due to variation in rainfall was greater than the reduction in water excess due to lucerne. This makes the decisions about when to grow lucerne to reduce water excess difficult if livestock enterprises are less profitable than cropping enterprises. The findings of this PhD indicate that lucerne does have a place in Mediterranean-type environments because of its greater water use than current farming practices. However, its use needs to be strategic and the strategy will vary from region to region. For example, in the low rainfall region lucerne sowings need to be matched with high soil water contents and phase length will generally be short (2-3 years). In comparison at high rainfall regions lucerne will need to be grown for longer or combined with other strategies to increase water use.
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Harlow, Jeanette. "Assessing Spatial and Temporal Patterns of Groundwater Recharge on Catalina Island, California, from Soil Water Balance Modeling." Thesis, California State University, Long Beach, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10743700.
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Quantifying groundwater recharge is of crucial importance for sustainable groundwater management. While many recharge quantification techniques have been devised, few provide spatially and temporally distributed estimates for regional-scale water resource assessments. In this study, a GIS-based and USGS-developed recharge quantification tool ? the Soil Water Balance (SWB) model ? was applied to produce fine-tuned recharge constraints and document spatial and temporal dynamics of recharge. SWB has, as of yet, been tested solely in coastal and continental temperate-humid climate zones. This study expands testing of SWB to a Mediterranean climate zone, focusing on Catalina Island, California. Catalina has experienced significant water supply issues due to a prolonged drought. Using available climate, land use/land cover and hydrology data, the SWB model yields annual recharge values for the time period 2008-2014 of 0.05 mm/year to over 82 mm/year. Results of this thesis provide information on spatial and temporal patterns of groundwater recharge on Catalina Island.
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Manyame, Comfort. "On farm yield and water use response of pearl millet to different management practices in Niger." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1203.
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Niaghi, Ali Rashid. "Advanced Evapotranspiration Measurement for Crop Water Management in the Red River Valley." Diss., North Dakota State University, 2019. https://hdl.handle.net/10365/31644.
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As the main component of terrestrial energy and water balance, evapotranspiration (ET) moves a large amount of water and energy in the form of latent heat flux from bare soil and vegetated surfaces into the atmosphere. Despite the development of many methods and equations through past decades, accurate ET estimation is still a challenging task, especially for the Red River Valley of the North (RRV) that has limited updated information on ET either for landscape or agricultural water management.
The overall objective of first study was to evaluate the ASCE-EWRI reference ET (ETo) method by developing an accurate crop coefficient (Kc) using an eddy covariance (EC) system over an unirrigated turfgrass site. The results showed that with mean ETgrass/ETo ratio as 0.96 for the entire growing seasons of turfgrass, the ASCE-EWRI ETo method is valid for guiding the turfgrass irrigation management in cold climate conditions. In a Controlled drainage with subirrigation (CD+SI) field, an EC system was used to measure and quantify energy flux components along with soil water content (SWC) and water table depth (WTD) measurements during four corn growing. This study showed that the subsurface drainage along with the CD + SI system can be used for optimal water management with an improvement of 26.7% and 6.6% of corn yield during wet and dry year, respectively.
For the final task, ET was measured using EC, Bowen ratio system (BREB), and soil water balance (SWB) method during the corn growing season. The comparison of the EC and the BREB system illustrated the advantages of using the residual method to close the energy balance closure of EC. Among the different time approaches for SWB method, ET by the SWB method using the average soil water contents between 24:00 to 2:00 time period showed non-significant differences (alpha = 0.05) compared to the BREB system during the observation periods.USDA National Institute of Food and Agriculture project
USDA NCR SARE project
ND Soybean Council
ND Water Resources Research Institute
ND Agricultural Experimental Station
USDA Hatch project
NASA ROSES Project
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Minasny, Budiman. "Efficient Methods for Predicting Soil Hydraulic Properties." Thesis, The University of Sydney, 2000. http://hdl.handle.net/2123/853.
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Both empirical and process-simulation models are useful for evaluating the effects of management practices on environmental quality and crop yield. The use of these models is limited, however, because they need many soil property values as input. The first step towards modelling is the collection of input data. Soil properties can be highly variable spatially and temporally, and measuring them is time-consuming and expensive. Efficient methods, which consider the uncertainty and cost of measurements, for estimating soil hydraulic properties form the main thrust of this study. Hydraulic properties are affected by other soil physical, and chemical properties, therefore it is possible to develop empirical relations to predict them. This idea quantified is called a pedotransfer function. Such functions may be global or restricted to a country or region. The different classification of particle-size fractions used in Australia compared with other countries presents a problem for the immediate adoption of exotic pedotransfer functions. A database of Australian soil hydraulic properties has been compiled. Pedotransfer functions for estimating water-retention and saturated hydraulic conductivity from particle size and bulk density for Australian soil are presented. Different approaches for deriving hydraulic transfer functions have been presented and compared. Published pedotransfer functions were also evaluated, generally they provide a satisfactory estimation of water retention and saturated hydraulic conductivity depending on the spatial scale and accuracy of prediction. Several pedotransfer functions were developed in this study to predict water retention and hydraulic conductivity. The pedotransfer functions developed here may predict adequately in large areas but for site-specific applications local calibration is needed. There is much uncertainty in the input data, and consequently the transfer functions can produce varied outputs. Uncertainty analysis is therefore needed. A general approach to quantifying uncertainty is to use Monte Carlo methods. By sampling repeatedly from the assumed probability distributions of the input variables and evaluating the response of the model the statistical distribution of the outputs can be estimated. A modified Latin hypercube method is presented for sampling joint multivariate probability distributions. This method is applied to quantify the uncertainties in pedotransfer functions of soil hydraulic properties. Hydraulic properties predicted using pedotransfer functions developed in this study are also used in a field soil-water model to analyze the uncertainties in the prediction of dynamic soil-water regimes. The use of the disc permeameter in the field conventionally requires the placement of a layer of sand in order to provide good contact between the soil surface and disc supply membrane. The effect of sand on water infiltration into the soil and on the estimate of sorptivity was investigated. A numerical study and a field experiment on heavy clay were conducted. Placement of sand significantly increased the cumulative infiltration but showed small differences in the infiltration rate. Estimation of sorptivity based on the Philip's two term algebraic model using different methods was also examined. The field experiment revealed that the error in infiltration measurement was proportional to the cumulative infiltration curve. Infiltration without placement of sand was considerably smaller because of the poor contact between the disc and soil surface. An inverse method for predicting soil hydraulic parameters from disc permeameter data has been developed. A numerical study showed that the inverse method is quite robust in identifying the hydraulic parameters. However application to field data showed that the estimated water retention curve is generally smaller than the one obtained in laboratory measurements. Nevertheless the estimated near-saturated hydraulic conductivity matched the analytical solution quite well. Th author believes that the inverse method can give a reasonable estimate of soil hydraulic parameters. Some experimental and theoretical problems were identified and discussed. A formal analysis was carried out to evaluate the efficiency of the different methods in predicting water retention and hydraulic conductivity. The analysis identified the contribution of individual source of measurement errors to the overall uncertainty. For single measurements, the inverse disc-permeameter analysis is economically more efficient than using pedotransfer functions or measuring hydraulic properties in the laboratory. However, given the large amount of spatial variation of soil hydraulic properties it is perhaps not surprising that lots of cheap and imprecise measurements, e.g. by hand texturing, are more efficient than a few expensive precise ones.
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Minasny, Budiman. "Efficient Methods for Predicting Soil Hydraulic Properties." University of Sydney. Land, Water & Crop Sciences, 2000. http://hdl.handle.net/2123/853.
Full textAbstract:
Both empirical and process-simulation models are useful for evaluating the effects of management practices on environmental quality and crop yield. The use of these models is limited, however, because they need many soil property values as input. The first step towards modelling is the collection of input data. Soil properties can be highly variable spatially and temporally, and measuring them is time-consuming and expensive. Efficient methods, which consider the uncertainty and cost of measurements, for estimating soil hydraulic properties form the main thrust of this study. Hydraulic properties are affected by other soil physical, and chemical properties, therefore it is possible to develop empirical relations to predict them. This idea quantified is called a pedotransfer function. Such functions may be global or restricted to a country or region. The different classification of particle-size fractions used in Australia compared with other countries presents a problem for the immediate adoption of exotic pedotransfer functions. A database of Australian soil hydraulic properties has been compiled. Pedotransfer functions for estimating water-retention and saturated hydraulic conductivity from particle size and bulk density for Australian soil are presented. Different approaches for deriving hydraulic transfer functions have been presented and compared. Published pedotransfer functions were also evaluated, generally they provide a satisfactory estimation of water retention and saturated hydraulic conductivity depending on the spatial scale and accuracy of prediction. Several pedotransfer functions were developed in this study to predict water retention and hydraulic conductivity. The pedotransfer functions developed here may predict adequately in large areas but for site-specific applications local calibration is needed. There is much uncertainty in the input data, and consequently the transfer functions can produce varied outputs. Uncertainty analysis is therefore needed. A general approach to quantifying uncertainty is to use Monte Carlo methods. By sampling repeatedly from the assumed probability distributions of the input variables and evaluating the response of the model the statistical distribution of the outputs can be estimated. A modified Latin hypercube method is presented for sampling joint multivariate probability distributions. This method is applied to quantify the uncertainties in pedotransfer functions of soil hydraulic properties. Hydraulic properties predicted using pedotransfer functions developed in this study are also used in a field soil-water model to analyze the uncertainties in the prediction of dynamic soil-water regimes. The use of the disc permeameter in the field conventionally requires the placement of a layer of sand in order to provide good contact between the soil surface and disc supply membrane. The effect of sand on water infiltration into the soil and on the estimate of sorptivity was investigated. A numerical study and a field experiment on heavy clay were conducted. Placement of sand significantly increased the cumulative infiltration but showed small differences in the infiltration rate. Estimation of sorptivity based on the Philip's two term algebraic model using different methods was also examined. The field experiment revealed that the error in infiltration measurement was proportional to the cumulative infiltration curve. Infiltration without placement of sand was considerably smaller because of the poor contact between the disc and soil surface. An inverse method for predicting soil hydraulic parameters from disc permeameter data has been developed. A numerical study showed that the inverse method is quite robust in identifying the hydraulic parameters. However application to field data showed that the estimated water retention curve is generally smaller than the one obtained in laboratory measurements. Nevertheless the estimated near-saturated hydraulic conductivity matched the analytical solution quite well. Th author believes that the inverse method can give a reasonable estimate of soil hydraulic parameters. Some experimental and theoretical problems were identified and discussed. A formal analysis was carried out to evaluate the efficiency of the different methods in predicting water retention and hydraulic conductivity. The analysis identified the contribution of individual source of measurement errors to the overall uncertainty. For single measurements, the inverse disc-permeameter analysis is economically more efficient than using pedotransfer functions or measuring hydraulic properties in the laboratory. However, given the large amount of spatial variation of soil hydraulic properties it is perhaps not surprising that lots of cheap and imprecise measurements, e.g. by hand texturing, are more efficient than a few expensive precise ones.
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Mahmud, Mir Nurul Hasan. "Minimum soil disturbance planting for rice-based rotations in northwest Bangladesh: Effects on plough pan and water balance." Thesis, Mahmud, Mir Nurul Hasan (2021) Minimum soil disturbance planting for rice-based rotations in northwest Bangladesh: Effects on plough pan and water balance. PhD thesis, Murdoch University, 2021. https://researchrepository.murdoch.edu.au/id/eprint/62402/.
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Soil degradation in the rice-based cropping system of Bangladesh has prompted research to switch from conventional tillage (CT) to minimum soil disturbance crop establishment, featuring strip planting (SP) and increased crop residue retention. However, the new residue retention levels and crop establishment methods need to be tested for their water use efficiency. Therefore, two field trials were initiated to evaluate the effects of SP and bed planting (BP) with increased crop residue retention on soil physical properties, components of the water balance and water productivity in two rice-based crop rotations. Field trials were conducted during 2015-2017 in two long-term conservation agriculture (CA) experimental fields established since 2010 in two regions of northwest Bangladesh, namely 1) Alipur, the alluvial soil region, and 2) Digram, the High Barind Tract (HBT) region. The trials consisted of three tillage treatments in the main plots - SP, BP and CT. The subplots comprised of two levels of residue retention - high residue (HR) and low residue (LR). High residue and LR treatment involved the retention of respectively 50 % and 20 % by the height of the previous crop, either anchored or loose. Strip planting and BP were done with a Versatile Multi-crop Planter mounted on a two-wheel tractor (2-WT).
Seven years of continuous CA practices have provided evidence that minimum soil disturbance and increased residue retention have altered the soil physical properties in both silty loam soil at Alipur and silty clay loam soil at Digram. The physical changes were reflected in the reduction of soil BD, enhancement of total porosity (TP) and reduction of penetration resistance (PR) in the 0-20 cm soil depth. High residue treatment reduced BD from 1.37 to 1.33 g cm-3 at Alipur and 1.27 to 1.24 g cm-3 at Digram soil in the 0-10 cm soil depth compared to the LR treatment. High residue retention increased macroporosity by an average of 55 % over LR treatment. Irrespective of residue retention, the average (two soils) decrease in BD was 4.5 % and 2.6 % in 0-10 cm depth for SP and BP treatment, respectively, compared to CT. The highest BD of 1.65 g cm-3 was achieved at 10-20 cm soil depth in the CT plot, which clearly indicates a massive plough pan at this depth. However, BD of the plough pan was reduced by 3.8 % in the SP and 4.6 % in the BP treatment indicating the amelioration of subsoil compaction due to the absence of puddling over seven years. Penetration resistance in the plough pan was also decreased from 2.15 MPa (CT) to 1.93 MPa (SP) at Alipur and 2.55 MPa (CT) to 2.32 MPa (SP) at Digram. In the silty loam soil, saturated hydraulic conductivity (Ksat) at 0-10 cm under CT was 1.00 cm hr-1 which was increased to 1.39 cm hr-1 by SP and to 1.52 cm hr-1 by BP. In the silty clay loam soil, Ksat at 0-10 cm was increased from 0.32 cm hr-1 under CT to 0.66 cm hr-1 by SP and to 0.81 cm hr-1 by BP. In 10-20 cm soil depth, Ksat increased from 0.22 cm hr-1 under CT to 0.48 cm hr-1 by SP and to 0.43 cm hr-1 by BP.
Soil compaction by a 2-WT with a single wheel-pass, two wheel-passes, and four wheel-passes with and without extra loading was also tested in non-CA fields adjacent to the two long-term trials. At 0-5 cm depth, soil BD with a single wheel pass was 1.37 g cm-3, which increased to 1.40 g cm-3 after two passes, and further increased to 1.47 g cm-3 with four passes. The BD of 0-5 cm depth with no extra loading was 1.37 g cm-3 which was increased to 1.39 g cm-3 with 100 kg extra loading and further increased to 1.43 g cm-3 with 200 kg extra loading. At 5-10 cm depth, compaction by CT involving four passes indicated that a 2-WT, when frequently trafficked at this depth for many years, creates a dense soil layer that is reasonably related to the formation of the plough pan. The least limiting water range (LLWR) range could be a good indicator of soil quality in soil compaction studies since the LLWR concept includes the effects of several growth-limiting factors such as matric potential, aeration and penetration resistance that are integrated into a single parameter. Conventional tillage had a larger LLWR which is also comparable to the LLWR of strip tillage single wheel pass treatment. Conservation agriculture practice facilitates tillage, fertilizer and seeding operation in a single pass. Thus, single wheel pass traffic by a low weight 2-WT may not create measurable compaction in the surface soil and the subsurface soil.
High rice residue retention treatment increased wheat yield by 7-18 % in the whole study period (2015-2017) compared to low residue retention. Strip planting increased wheat yield by 18-25 % compared to CT in the three years. By contrast, BP increased wheat yield by 16 % compared to CT in 2015 but not in 2016 or 2017. Strip planting saved 15-36 % irrigation water for wheat growth compared to CT in three years. In contrast to SP, BP saved only 8-25 % irrigation water than CT. Irrigation water productivity of wheat was higher under SP (2.2 kg m-3) than that under BP (1.7 kg m-3) and CT (1.3 kg m-3). The results suggest that SP performed better than BP in terms of crop productivity and irrigation water productivity.
Total water losses under SP continuous flooding irrigation were 80.0-125.0 cm, while the values were 82.0-123.0 cm for BP and 66.0-86.0 cm for CT. Deep drainage during the rice crop for SP, BP and CT accounted for about 41 %, 44 %, and 39 % of the total loss, respectively. Alternate wetting and drying irrigation reduced the drainage losses by 35 %, 26 % and 48 % for SP, BP and CT, respectively. The yield of rice ranged from 6.1-6.9 t ha-1, 6.1-6.6 t ha-1 and 6.5-6.7 t ha-1 for SP, BP and CT, respectively. Irrigation water productivity for rice was higher under CT (0.88 kg m-3) compared to SP (0.66 kg m-3) and BP (0.60 kg m-3).
Improved crop yield under SP with residue retention should encourage smallholder farmers to adopt minimum soil disturbance planting in the rice-based rotation. However, altered water balance in the non-puddled minimum soil disturbance plot may require more irrigation for rice while allowing greater infiltration to groundwater. In contrast, for wheat, SP and HR had positive effects on water use and water productivity. Since water lost by deep percolation returns to the groundwater and is potentially available for reuse, non-puddled rice can beneficially increase groundwater recharge when practised in a large command area. Hence, CA practices appear to decrease the requirement for groundwater for irrigation of dry season wheat while increasing the potential for groundwater recharge, but this needs further investigation.
Keywords: Barind area (Bangladesh); bed planting; conservation agriculture; conventional tillage; deep drainage; least limiting water range; minimum soil disturbance; number of wheel passes; soil compaction; strip planting; water balance.
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Sun, Jian. "Parameter estimation of coupled water and energy balance models based on stationarity constraints of soil moisture and temperature." Thesis, Boston University, 2012. https://hdl.handle.net/2144/31613.
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Thesis (Ph.D.)--Boston UniversityPLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.
A new method is developed for estimating the parameters of land surface water and energy balance models through enforcement of stationary constraints on soil moisture and temperature. Through conditional averaging of the water balance equation with respect to soil moisture and the energy balance equation with respect to surface temperature, a measure of stationarity is derived that approximates the errors present in predicted fluxes (e.g. evaporation, runoff, sensible heat, ground conduction) in terms of measured model inputs (e.g. precipitation, radiation, soil moisture and temperature). Minimization of the approximated error yields estimates of model parameters. The approach is distinct from traditional model calibration because the minimized error term does not depend on measurements of the predicted fluxes. This proposed method is applied to a land surface water and energy balance model similar to those used in global climate models. The approach is tested at two Ameriflux sites with continuous in-situ measurements of soil moisture, temperature, radiation, and surface turbulent fluxes (evapotranspiration and sensible heat). Fluxes estimated with the proposed method match field measurements approximately as well as those estimated by traditional calibration. Replacing the in-situ land surface temperature and soil moisture with estimates retrieved from satellite leads to minimal degradation of model performance. Sensitivity analysis at these sites demonstrates that increasing model complexity does not improve performance. With promising results from testing the approach at these field sites, the method is applied to estimate evapotranspiration over the Southern Great Plains region of North America. In this test, archived meteorological data and remotely sensed moisture and temperature are used to force the model. The spatial pattern of estimated mean annual evapotranspiration is in good agreement (RMSE of 8 Wm-2 , R 2 of 0.75) with published estimates derived from measured precipitation and streamflow. Estimated parameters are reasonably distributed and consistent with climate and vegetation patterns over the region. Because there are so few sites on earth where surface turbulent fluxes are measured, the proposed approach is more widely applicable than traditional calibration methods, and thus could be used, with satellite data, to estimate maps of land surface parameters required by global climate models.
2031-01-01
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Fabres, Tanira Marinho. "Classificação climática segundo Köppen e Thornthwaite e caracterização edafoclimática referente à região de Santa Maria, RS." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/11/11136/tde-24062009-091549/.
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O presente trabalho foi desenvolvido com objetivo de analisar a classificação climática segundo Köppen e Thornthwaite (comparando os valores de armazenamento de água no solo, evapotranspiração real, deficiência hídrica e excedente hídrico para realização do balanço hídrico cíclico mensal), e de propor uma caracterização edafoclimática referente à região mesoclimática de Santa Maria, RS utilizando uma série histórica de 35 anos (de 1969 a 2003). De acordo com os resultados, as seguintes conclusões podem ser apresentadas: (a) a classificação climática segundo Thornthwaite ou Köppen pode ser feita com base na classe mais freqüente ou utilizando os valores médios de temperatura e de chuva e a capacidade de água disponível de 50 mm; (b) classificação climática segundo Thornthwaite: A r B\'3 a\' (classe mais freqüente) ou B4 r B\'3 a\' (utilizando os valores médios de temperatura e de chuva); (c) classificação climática segundo Köppen: Cfga (classe mais freqüente) ou Cwga (utilizando os valores médios de temperatura e de chuva); e (d) A29/42S,53/42W,95,35,11,7,27,2,20,3,5,5,471,1/5,1235,2672,1802,20,953,887,915,50: caracterização edafoclimática proposta. Isso significa que a evapotranspiração real é pelo menos 90% da evapotranspiração potencial de referência (classe A de disponibilidade hídrica), a localização geográfica é de 29o42\' (latitude sul), 53o42\' (longitude oeste) e altitude de 95 m, e que a série histórica apresenta 35 anos, sendo as temperaturas mínima e máxima mensal de 11oC (julho) e 27oC (fevereiro), a temperatura média anual de 20oC, respectivamente, com coeficiente de variação de 3%, e as chuvas mínima e máxima mensal de 5 mm (maio) e 471 mm (janeiro/maio), as chuvas mínima, máxima e média anual de 1235 mm, 2672 mm e 1802 mm, respectivamente, com coeficiente de variação de 20%, valores médios anuais de evapotranspiração potencial de referência, evapotranspiração real e excedente hídrico de 953 mm, 887 mm e 915 mm, respectivamente, adotando uma capacidade de água disponível de 50 mm.The present work was developed with the purpose of analyzing the climatic classification by Köppen and Thornthwaite (comparing the values of soil water holding, actual evapotranspiration, water deficit and water excess for cyclic water balance using monthly data), and of proposing an edaphoclimatic characterization related to the mesoclimatic region of Santa Maria, State of Rio Grande do Sul, Brazil, using a historical series of 35 years (from 1969 to 2003). According to the results, the following conclusions can be presented: (a) the climatic classification by Thornthwaite or Köppen can be done based on the modal class or using the mean values of air temperature and rainfall and the soil water holding capacity of 50 mm; (b) the climatic classification by Thornthwaite is A r B\'3 a\' (modal class) or B4 r B\'3 a\' (using the mean values of temperature and rainfall); (c) the climatic classification by Köppen is Cfga (modal class) or Cwga (using the mean values of temperature and rainfall); and (d) A29/42S,53/42W,95,35,11,7,27,2,20,3,5,5,471,1/5,1235,2672,1802,20,953,887,915,50 is the proposed edaphoclimatic characterization. It means the actual evapotranspiration is at least 90% of the potential evapotranspiration (class A of soil water availability), the geographic localization is 29o42\' South (latitude), 53o42\' West (longitude) and altitude of 95 m, using a historic series of 35 years, being monthly minimum and maximum air temperatures of 11oC (July) and 27oC (February), the annual mean air temperature of 20oC, with coefficient of variation of 3%, and the monthly minimum and maximum rainfall of 5 mm (May) and 471 mm (January/May), the annual minimum, maximum and mean rainfall of 1235 mm, 2672 mm and 1802 mm, respectively, with coefficient of variation of 20%, and the annual mean values of potential evapotranspiration, actual evapotranspiration and water excess of 953 mm, 887 mm and 915 mm, respectively, using a soil water holding capacity of 50 mm.
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Dlamini, Musa V. "Short-Term Water Use Dynamics in Drainage Lysimeters." DigitalCommons@USU, 2003. https://digitalcommons.usu.edu/etd/5877.
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Turfgrass water use (seasonal turfET) and crop coefficients were determined and a mathematical soil-water balance model for non-weighing drainage lysimeters, which simulates the occurrence (timing and amount) of drainage, was developed. Pairs of non-weighing drainage lysimeters were used to determine crop coefficients for turfgrass in four locations in the state of Utah: Logan Golf and Country Club, Murray Golf Course, Brigham Young University (Spanish Fork) Experiment Farm, and Sunbrook Golf Course (St. George).
Daily weather data including air temperature, relative humidity, average wind travel, total solar radiation, precipitation, and average soil temperature were collected with an electronic weather station at each site. Daily precipitation was measured in three sites throughout the season: Murray, Spanish Fork, and Sunbrook. At Logan Golf and Country Club, precipitation was measured to November 10,2002.
Water use (averages of two lysimeters) during the growing season varied from 684 to 732 mm for three years (2000- 2002) for the mid-April through late-October observation period at Logan Golf Course; 699 mm for May through October at Murray; 469 mm at Spanish Fork; and 896 mm for late-February through early November at Sunbrook, for 2002 growing season. Calculated seasonal Etr using the 82 Kimberly Penman equation with a 1 00-miles-per-day wind travel limit varied from 1166 to 1229 mm at Logan Golf and Country Club, 1067 mm at Murray, 839 mm at Spanish Fork, and 1574 mm at Sunbrook. Seasonal Etr calculated using the PM ASCE std Etr equation was greater than the 82 Kimberly Peru11an . Seasonal Eto calculated using the FAO#56 Eto equation was less than both the 82 Kimberly Penman and the PM ASCE std Etr equations.
Calculated crop coefficients (as a ratio of measured crop water use and calculated potential evapotranspiration) based on alfalfa reference evapotranspiration with the 1982 Kimberly-Penman equation averaged 0.58 for the three years at Logan. Seasonal averages varied from 0.57 to 0.60. Seasonal crop coefficients (2002) were 0.57 for Logan, Spanish Fork, and Sunbrook, and 0.65 for Murray. Short-period crop coefficients also varied within a given season. Short-term crop coefficients derived from a time of wetting and drainage experiment averaged 0.55 at Logan, 0.56 at Murray, 0.60 at Spanish Fork, and 0.56 at Sunbrook.
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Buckley, Meghan Elizabeth. "Effect of tillage on the hydrology of claypan soils in Kansas." Diss., Manhattan, Kan. : Kansas State University, 2008. http://hdl.handle.net/2097/943.
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Mota, Jaedson Cláudio Anunciato. "Componentes do balanço de água em um Cambissolo cultivado com meloeiro irrigado por gotejamento, com e sem cobertura da superfície." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/11/11140/tde-16032010-160217/.
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O conhecimento sobre o balanço de água no solo é essencial ao manejo do sistema solo-água- planta. Esta pesquisa objetivou estudar os componentes do balaço de água em Cambissolo cultivado com meloeiro irrigado por gotejamento, com e sem cobertura da superfície, em Baraúna-RN. Em área experimental de 20 m x 50 m cultivou-se melão Amarelo, variedade AF- 646, no espaçamento de 2,00 m x 0,35 m, num total de dez linhas de plantas de 50 m de extensão cada. A 1/3 e 2/3 da extensão de cada linha de plantas foram instalados quatro tensiômetros, um em cada uma das profundidades 0,1; 0,2; 0,3 e 0,4 m. A instalação foi feita adjacente à linha de irrigação (0,1 m da linha de plantas) entre duas plantas selecionadas, com os tensiômetros espaçados 0,1 m entre si. Em cinco linhas aleatórias fez-se a cobertura com folhas secas de bananeira (Musa sp.) ao longo da linha de gotejamento numa faixa de 0,5 m. Nas outras cinco manteve-se o cultivo sem cobertura. Assim, o experimento consistiu de dois tratamentos, com dez repetições, em quatro períodos fenológicos: inicial (7-22 DAS dias após a semeadura), vegetativo (22-40 DAS), frutificação (40-58 DAS) e maturação (58-70 DAS). As precipitações pluviais foram medidas com pluviômetro e as armazenagens de água estimadas pelo método do trapézio, a partir das leituras dos tensiômetros e das curvas de retenção. Para a determinação das densidades de fluxo de água no limite inferior do volume de controle de solo (0,3 m), foram considerados os tensiômetros nas profundidades 0,2; 0,3 e 0,4 m, sendo que o tensiômetro a 0,3 m foi utilizado para estimar o conteúdo de água no solo, com uso da curva de retenção de água para esta profundidade, e os outros dois para o cálculo do gradiente de potencial total. As densidades de fluxo foram calculadas pela equação de Darcy-Buckingham, com a condutividade hidráulica do solo determinada pelo método do perfil instantâneo. O deflúvio superficial foi desconsiderado e a evapotranspiração real da cultura foi calculada pela equação do balanço de massas. Concluiu-se que: a) à 0,2 m de profundidade a condutividade hidráulica do solo foi baixa; b) o manejo da irrigação com tensiômetros permitiu redução de 45% na lâmina de água em relação à usualmente praticada na região, sem afetar a produtividade da cultura; c) houve efeito positivo da cobertura do solo sobre a armazenagem de água, especialmente nos estádios inicial e vegetativo da cultura; d) o método do balanço de água no solo mostrou-se eficiente na estimativa da evapotranspiração real, em condições de cultivo de meloeiro irrigado; e) a aplicação de uma única lâmina diária de irrigação, mesmo em curto intervalo de tempo, apresenta risco de perda de água por drenagem interna, especialmente nas fases inicial e vegetativa do meloeiro; f) a variabilidade espacial da densidade de fluxo foi elevada quando houve ocorrência de precipitação pluvial; g) não houve efeito da cobertura do solo na evapotranspiração da cultura, nem sobre a produtividade e características pós-colheita dos frutos; h) a curva de coeficiente de cultivo apresenta grandes limitações quando utilizada para fornecer água para o meloeiro.The knowledge about the soil water balance is essential to soil-water-plant system management. Thus, this research aimed to study the water balance components in an Inceptsol cropped with muskmelon under drip irrigation, with and without surface covering, in the county of Baraúna, Rio Grande do Norte State, Brazil (05º04\'48 S, 37º37\'00 W). In an experimental area of 20 m x 50 m grew up AF-646 muskmelon, spaced 2.00 m x 0.35 m, in a total of ten plants lines 50 m long each. At 1/3 and 2/3 of the length of each plant line, four tensiometers were installed, one in each depths of 0.1, 0.2, 0.3 and 0.4 m. The installation was made adjacent to the irrigation line (0.1 m from the plant line) between two selected plants 0.1 m apart. In five random lines, it was made a covering with dry leaves of banana (Musa sp.) along the drip line in the range of 0.5 m. In the other five there was no covering. Thus, the experiment consisted of two treatments whith ten repetitions in four phenological stages: initial (7-22 DAS - days after sowing), growing (22-40 DAS), fruiting (40-58 DAS) and maturing (58-70 DAS). Rainfall was measured with rain gauge and water storage estimated by trapezoidal method, from tensiometer readings and retention curves. To determine the soil water flux densities at the soil depth 0.3 m, tensiometers at depths 0.2, 0.3 and 0.4 m were considered; the tensiometer at 0.3 m was used to estimate the soil water content, from the soil water retention curve at this depth, and the other two to calculate the soil water total potential gradient. The flux densities were calculated by the Darcy-Buckingham equation, with the hydraulic conductivity being determined by the instantaneous profile method. There was no runoff and the crop actual evapotranspiration was calculated by the mass balance equation. It could be concluded that: a) at 0.2 m soil depth the hydraulic conductivity was low; b) controlled irrigation with tensiometers allowed a reduction of 45% in water application in relation to commonly used practice in the region, without crop productivity change; c) there was positive effect of soil covering on water storage, especially at the initial and vegetative stages; d) the method of soil water balance was efficient to estimate actual evapotranspiration, under irrigated muskmelon conditions; e) the application of a single irrigation depth daily, even in a short time period, presents risk of water to be lost by internal drainage, especially at initial and vegetative muskmelon stages; f) the spatial variability of soil water flux density was high when rainfall incidence occurred; g) there was no effect of covering on crop actual evapotranspiration, neither on yield and post-harvest fruits characteristics; h) the crop coefficient curve has severe limitations when used to provide water to the muskmelon.
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Poulter, Rachel. "Investigating the role of soil constraints on the water balance of some annual and perennial systems in a Mediterranean environment /." Connect to this title, 2005. http://theses.library.uwa.edu.au/adt-WU2006.0018.
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Manikku, Acharige Niranjan Sanjeeva Wimalathunge. "Space-time modelling of soil moisture: prediction and forecasting for improved agricultural management." Thesis, The University of Sydney, 2019. http://hdl.handle.net/2123/21122.
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Knowledge of soil moisture is crucial in every agricultural system. Accurate soil moisture estimates are valuable guides to management decisions such as crop selection and estimation of yield potential. However, soil moisture is highly variable temporally and spatially in the landscape and very challenging to monitor. Existing soil moisture monitoring approaches lack in appropriate resolution for current agricultural requirements. Therefore, this thesis develops novel space-time models for predicting and forecasting soil moisture at a 90 m spatial resolution. A water balance model (unsaturated and multi-layer) was presented to estimate soil moisture with a combination of soil moisture sensing, remote sensing and readily available geospatial data, which parameterise the soil water balance equation. The model was further improved by optimising the parameters (infiltration and evapotranspiration) and using machine learning techniques. The prediction quality was reasonable: topsoil (Concordance = 0.69, Accuracy = 0.05 cm3cm-3); subsoil (Concordance = 0.72, Accuracy = 0.04 cm3cm-3); and root-zone (Concordance = 0.75, Accuracy = 0.05 cm3cm-3). Also, three farm-scale soil moisture surveys were performed using a mobile cosmic-ray probe platform at strategic time points of the farming year. Estimates were validated with the soil moisture obtained from 0-30 cm soil layer (Concordance = 0.87, Accuracy = 0.05 cm3cm-3). Moreover, a model (stochastic plus machine learning) was presented to forecast soil moisture: one month; three months; and six months into the future. One month lead times had the greatest forecast quality (Concordance > 0.9, Accuracy < 0.02) with the forecast quality declining with longer lead times. The subsoil was more forecastable than the topsoil. Thus, these new approaches for soil moisture modelling would have real utility across agricultural regions of Australia where they are likely to be most beneficial in management of agri-food production systems.
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Gonçalves, Marta Filipa Dores Martins. "Influência da rega subsuperficial e gota-a-gota na utilização da água , qualidade e produção em pereira (Pyrus communis L.) Rocha. Estudo preliminar." Master's thesis, ISA, 2010. http://hdl.handle.net/10400.5/6560.
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Mestrado em Engenharia Agronómica - Instituto Superior de AgronomiaWith the aim of comparing the physiologic response, the quality of the fruits and water productivity of a pear orchard irrigated by two different irrigation systems, a field trial was conducted on a 4 year old „Rocha‟ / Sydo pear orchard, irrigated by surface drip and subsurface drip irrigation, during the year 2009/2010. There are no differences in the flower bloom and fruit setting, sugar content and acidity of the fruits between the two irrigation systems, but the surface drip irrigation produced a larger percentage of fruits > 70 mm than subsurface drip irrigation. The subsurface system had lower soil water evaporation (124.8 mm and 148.4 mm for the subsurface system and surface drip, respectively) and increased water productivity (3.82 Kg.m3 for subsurface and 3.09 Kg.m3 for surface drip). For the same amount of water supplied, the subsurface irrigation had a 23.3% higher yield than surface drip, resulting also in a higher dry matter production by water used by the trees. The average cultural coefficient (Kc) of the orchard in the period 8 April to 31 August was 0.96.
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Poulter, Rachel. "Investigating the role of soil constraints on the water balance of some annual and perennial systems in a Mediterranean environment." University of Western Australia. Faculty of Agriculture, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0018.
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This thesis compares the in situ water balance of common annual production systems (wheat, lupin, subclover and serradella) with a grazed perennial system (lucerne) at a site in the Avon Catchment, Western Australia. Using a physically-based water balance approach the value of a plant based solution in redressing the hydrological imbalance that has become a feature of much of the dryland agricultural region of Western Australia is investigated. The effectiveness of lucerne in providing greater available storage for buffering large rainfall events, as compared to the annual systems, is illustrated. Continued transpiration following out-of-season rainfall events maintains a larger available storage capacity. In contrast, the annual systems that are fallow over summer only withdrew a small fraction of water by soil evaporation between rainfall events. Under annual systems, the profile moisture store was sequentially increased to the extent that additional increments of rainfall could potentially contribute to deep drainage. A particular focus of this study has been to investigate the presence of soil constraints to root growth, and to assess how these constraints affect the water balance. A site survey indicated the soil penetration resistance was sufficient to impose a physical constraint to root growth. Published literature on the site shows soil acidity is also at a level imposing chemical constraints to root growth. A root growth model “Rootmodel”, for predicting root growth with and without soil constraints is examined in detail as a method for providing root growth parameters for inclusion into the numerical water balance model, SWIM based on Richard’s equation. Functions developed from “Rootmodel” adequately describe the effect of profile limitations to root growth, such as soil strength, moisture availability and temperature. Recommendations are made for inclusion of a growth suppressing function in “rootmodel” based on the chemical limitation of low pH. The effects of soil acidity on the root growth of several species is investigated experimentally and the resultant root data provided a reference point by which the simplified prediction of root growth built into SWIM could be adjusted using a linear reduction function. A similar linear reduction function is also employed to impose a physical constraint in the form of high penetration resistance.
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Sehgal, Vinit. "Near Real-time Seasonal Drought Forecasting and Retrospective Drought Analysis using Simulated Multi- layer Soil Moisture from Hydrological Models at Sub- Watershed Scales." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/78623.
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This study proposes a stratified approach of drought severity assessment using multi-layer simulated soil moisture. SWAT (Soil and Water Assessment Tool) models are calibrated for 50 watersheds in the South-Atlantic Gulf region of the Southeastern US and a high-resolution daily soil moisture dataset is obtained at Hydrologic Unit Code (HUC-12) resolution for a period of January 1982 through December 2013. A near real-time hydrologic simulation framework by coupling the calibrated SWAT models with the National Centers for Environmental Prediction (NCEP) coupled forecast system model version 2 (CFSv2) weather data is developed to forecast various water balance components including soil moisture (SM), actual evapotranspiration (ET), potential evapotranspiration ET (PET), and runoff (SURQ) for near-real time drought severity assessment, and drought forecasting for a lead of 9-months. A combination of the surface and total rooting depth soil moisture percentiles proves to be an effective increment over conventional drought assessment approaches in capturing both, transient and long-term drought impacts. The proposed real-time drought monitoring approach shows high accuracy in capturing drought onset and propagation and shows a high degree of similarity with the U.S. Drought Monitor (USDM), the long-term (PDSI, PHDI, SPI-9 and SPI-12), and the short-term (Palmer Z index, SPI-1 and SPI-6) drought indices.Master of Science