The continued spread of glyphosate-resistant common waterhemp [Amaranthus tuberculatus (Moq.) Sauer (syn. rudis)] and Palmer amaranth [Amaranthus palmeri (S. Wats.)] have complicated weed control efforts in soybean and corn production in Illinois. A thorough understanding of the weed biology of these species is fundamental in developing effective weed management strategies. The determination of emergence patterns as well as the influence of tillage practices on soil microclimate and soil seed bank will allow control strategies to be implemented at the most effective timing. Field experiments were conducted in southern Illinois throughout the growing season of 2013 and 2014 on two separate sites with populations of common waterhemp and Palmer amaranth. Three tillage treatments were evaluated: no-tillage; early tillage, preferably performed around a recommended soybean planting date of May 1st; and late tillage, preferably performed on June 1st to simulate a late soybean planting. Amaranthus seedlings were identified and enumerated in the center 1 m2 quadrat of each plot within a 7-day interval from April through November or first frost. All weed seedlings were removed from the plot area after each enumeration. Soil temperature and soil moisture were recorded hourly throughout the experiment using data loggers established in the plot area. First emergence of common waterhemp occurred earlier in the season than did Palmer amaranth. In 2013, initial emergence of common waterhemp and Palmer amaranth was observed at the first and second week of May, respectively. In 2014, initial common waterhemp emergence was observed in late April, while Palmer amaranth initial emergence was similar to previous year. Palmer amaranth emerged over a longer period compared to waterhemp. By the end of June, 90% of common waterhemp had emerged regardless of tillage or year. By the same measure, Palmer amaranth emergence was extended to the third week of July and second week of August in 2013 and 2014, respectively. Soil temperature did not differ across tillage treatments in both years. On the other hand, differences in soil moisture were observed, mostly over two weeks following each tillage operation. The single best predictor for common waterhemp emergence was soil temperature (weekly highs and lows) followed by soil moisture. For Palmer amaranth emergence the single best predictor was spikes in soil moisture (high for the week). In 2013, common waterhemp emergence was initially positively and later in the growing season negatively interacted with maximum temperature 13 days prior to counts, with temperatures above 30 C observed with decreased emergence (R2 = 0.35). In the same year spikes in soil moisture interacted with Palmer amaranth emergence were those observed 11 days before each seedling enumeration date (R2 = 0.30). In 2014, with first common waterhemp emergence in April, a positive interaction to high soil temperature was initially observed followed by a positive interaction to minimum temperatures later in the season (R2 = 0.55). Spikes in soil moisture observed 2 weeks prior to emergence and weekly high temperatures 8 days prior to emergence were the best predictors of Palmer amaranth emergence in 2014 (R2 =0.37). Soil seed bank depletion was also estimated by comparing field emergence with greenhouse experiment results of soil seed bank estimation. Greater emergence of common waterhemp from the soil seed bank was observed in early tillage in 2013 and no-tillage in 2014 than late tillage, respectively; for Palmer amaranth, the greatest emergence from the soil seed bank was observed in no-tillage and late tillage in 2013, and no-tillage, in 2014. The emergence patterns observed in this research suggest that although common waterhemp and Palmer amaranth exhibit discontinuous emergence throughout the growing season, greater attention should be placed on managing peaks of emergence from late April to late July, which is critical to provide a foundation for early-season weed management. Furthermore, knowledge regarding the emergence patterns of common waterhemp and Palmer amaranth combined with monitoring environmental factors such as soil moisture and soil temperature may assist efforts for scouting fields to determine the likely presence of these weed species. The timing of viable postemergence herbicide options for control of glyphosate-resistant waterhemp and Palmer amaranth is critical and monitoring weather patterns to direct scouting efforts may improve the timeliness of these postemergence applications.

xvi, 156 p. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / This dissertation examined a number of general vegetation-modeling issues, and the sensitivity of terrestrial net primary productivity (NPP), soil moisture and actual evapotranspiration (ET) to climatic variations in China. The specific issues addressed included: (1) the sensitivity of the performance of an equilibrium vegetation model to the choice of monthly-mean climatologies, observed validation data sets, and three map-comparison approaches; and (2) the limitations of existing map-comparison approaches in vegetation modeling; and the variation and climate sensitivity of (3) terrestrial NPP and (4) soil moisture and actual ET in China. To address the first issue, BIOME4 (Kaplan et al., 2002), a typical example of an equilibrium vegetation model, was used along with a set of 19 different monthly-mean climatologies, three validation data sets, and several map-comparison methods. To address the second issue, the "opposite and identity" (01) index (Tang, 2008) was developed for evaluating the correspondence of two simulation results. To examine the third issue, a set of historical NPP dynamics were derived from normalized-difference vegetation index data by modifying the CASA (Potter et al., 1999) approach and then were linked to the variation of temperature and precipitation to analyze the climatic effects on terrestrial NPP in China. To examine the fourth issue, a stand-alone water balance model, LH (LPJ-hydrology), was developed by modifying the LPJ dynamic global vegetation model (Sitch et al., 2003), and applying it to a China case study. The results of these analyses indicate that (1) the 30-year mean-climatology preceding the observed data produces the most accurate vegetation simulations; (2) the OI index is a useful tool to compare two simulation results or to evaluate simulation results against observed spatiotemporal data; (3) climate and land-use change jointly controlled NPP dynamics in the eastern monsoon zone of China. In contrast, NPP dynamics in the north-west and zone and in the Tibet Plateau frigid zone depended more on climatic variation; and (4) the spatial patterns of soil moisture and ET in China were correlated with the variation of temperature and precipitation. However, the strength of such relationship varies spatially. This dissertation includes my published and coauthored materials. / Adviser: Patrick J. Bartlein

Made available in DSpace on 2014-06-11T19:31:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2003-12-18Bitstream added on 2014-06-13T19:41:53Z : No. of bitstreams: 1 fontes_ir_dr_botfca.pdf: 6105136 bytes, checksum: 23e89a651c99005b7465ec2d3aae3e9b (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O presente trabalho teve como objetivo a configuração de um sistema de supervisão e controle de irrigação utilizando técnicas de inteligência artificial. De acordo com metodologia adotada, o seu desenvolvimento foi realizado em três fases distintas. Inicialmente foram construídos os seguintes módulos de hardware: Unidade de Sensores, Unidade Concentradora de Dados e Sensor de Umidade do Solo do tipo Capacitivo. Em seguida foi criada uma aplicação através do programa de supervisão e controle do tipo SCADA, Elipse PRO, dedicada à supervisão e controle de uma casa de vegetação. Na fase final foram coletados os dados necessários para o treinamento de uma rede neural artificial que é parte integrante do sensor de umidade de solo do tipo capacitivo. Os resultados obtidos através de um conjunto de teste de medidas demonstraram que o sensor capacitivo apresenta comportamento e desempenho similares ao do sensor de do tipo TDR, o que permite concluir que esta solução pode representar uma significativa contribuição, viabilizando a implantação de sistemas de supervisão e controle em processos de irrigação com uma relação custo/benefício em níveis aceitáveis. / The present work had as objective the configuration of a supervisory and control system for irrigation using artificial intelligence techniques. In agreement with adopted methodology, its development was accomplished in three different phases. Initially the following hardware modules were built: Sensors Unit, Data Concentrator Unit and a Capacitive type Soil Moisture Sensor. Soon afterwards an application was created through the supervisory and control program of the type SCADA, Ellipse PRO, dedicated to the supervision and control of a green house. In the final phase the necessary data were collected for the training of an artificial neural network that is integral part of the capacitive type soil moisture sensor. With the application developed in the Ellipse PRO a database was created for the training of the artificial neural network, containing a group of 2440 measures of soil moisture obtained through a capacitive type sensor and a TDR type sensor. The results obtained through a group of test of measures demonstrated that the capacitive sensor presents a similar behavior to the of the TDR type sensor, the one that allows conclude that this solution can represent a significant contribution, making possible the implantation of supervisory and control systems in irrigation processes with a cost/benefit relationship in acceptable levels.

abstract: Biological soil crusts (BSCs) dominate the soil surface of drylands in the western United States and possess properties thought to influence local hydrology. Little agreement exists, however, on the effects of BSCs on runoff, infiltration, and evaporative rates. This study aims to improve the predictive capability of an ecohydrology model in order to understand how BSCs affect the storage, retention, and infiltration of water into soils characteristic of the Colorado Plateau. A set of soil moisture measurements obtained at a climate manipulation experiment near Moab, Utah, are used for model development and testing. Over five years, different rainfall treatments over experimental plots resulted in the development of BSC cover with different properties that influence soil moisture differently. This study used numerical simulations to isolate the relative roles of different BSC properties on the hydrologic response at the plot-scale. On-site meteorological, soil texture and vegetation property datasets are utilized as inputs into a ecohydrology model, modified to include local processes: (1) temperature-dependent precipitation partitioning, snow accumulation and melt, (2) seasonally-variable potential evapotranspiration, (3) plant species-specific transpiration factors, and (4) a new module to account for the water balance of the BSC. Soil, BSC and vegetation parameters were determined from field measurements or through model calibration to the soil moisture observations using the Shuffled Complex Evolution algorithm. Model performance is assessed against five years of soil moisture measurements at each experimental site, representing a wide range of crust cover properties. Simulation experiments were then carried out using the calibrated ecohydrology model in which BSC parameters were varied according to the level of development of the BSC, as represented by the BSC roughness. These results indicate that BSCs act to both buffer against evaporative soil moisture losses by enhancing BSC moisture evaporation and significantly alter the rates of soil water infiltration by reducing moisture storage and increasing conductivity in the BSC. The simulation results for soil water infiltration, storage and retention across a wide range of meteorological events help explain the conflicting hydrologic outcomes present in the literature on BSCs. In addition, identifying how BSCs mediate infiltration and evaporation processes has implications for dryland ecosystem function in the western United States. / Dissertation/Thesis / Masters Thesis Geological Sciences 2015

abstract: The history of outdoor water use in the Phoenix, Arizona metropolitan area has given rise to a general landscape aesthetic and pattern of residential irrigation that seem in discord with the natural desert environment. While xeric landscaping that incorporates native desert ecology has potential for reducing urban irrigation demand, there are societal and environmental factors that make mesic landscaping, including shade trees and grass lawns, a common choice for residential yards. In either case, there is potential for water savings through irrigation schedules based on fluxes affecting soil moisture in the active plant rooting zone. In this thesis, a point-scale model of soil moisture dynamics was applied to two urban sites in the Phoenix area: one with xeric landscaping, and one with mesic. The model was calibrated to observed soil moisture data from irrigated and non-irrigated sensors, with local daily precipitation and potential evapotranspiration records as model forcing. Simulations were then conducted to investigate effects of irrigation scheduling, plant stress parameters, and precipitation variability on soil moisture dynamics, water balance partitioning, and plant water stress. Results indicated a substantial difference in soil water storage capacity at the two sites, which affected sensitivity to irrigation scenarios. Seasonal variation was critical in avoiding unproductive water losses at the xeric site, and allowed for small water savings at the mesic site by maintaining mild levels of plant stress. The model was also used to determine minimum annual irrigation required to achieve specified levels of plant stress at each site using long-term meteorological records. While the xeric site showed greater potential for water savings, a bimodal schedule consisting of low winter and summer irrigation was identified as a means to conserve water at both sites, with moderate levels of plant water stress. For lower stress levels, potential water savings were found by fixing irrigation depth and seasonally varying the irrigation interval, consistent with municipal recommendations in the Phoenix metropolitan area. These results provide a deeper understanding of the ecohydrologic differences between the two types of landscape treatments, and can assist water and landscape managers in identifying opportunities for water savings in desert urban areas. / Dissertation/Thesis / M.S. Civil and Environmental Engineering 2013

Transport of chemical substances through a catchment depend to a large extent on the water content of the soil through which they are transported. When the groundwater level rise and fall, redox conditions change in the soil and the transport of substances is affected. The aim of this study is to develop a hydrological model which is able to simulate soil water content at different depths and groundwater level in a soil profile. A new type of conceptual model is developed, which uses a continous represenation of the soil and soil water from the soil surface down to the bedrock. The model is intended to be applied on small catchments at a later stage. The results show that the simulation of groundwater levels was greatly improved compared to previous results. Simulation of soil water content at selected depths is not yet satisfactory. The runoff simulation was accurate at one of the sites but did not work as well at the other. At one of the sites it was also possible to combine good simulations of runoff and groundwater levels but at the other it was only possible to obtain acceptable simulations of either runoff or groundwater. It is suggested that model performance could be improved by letting the porosity decrease and the soil water content increase non-linearly with depth. Calculations of evaporation from soil and runoff also need to be modified.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / This work seeks to integrate climatic, hydrologic, and reservoir operation models in order to optimize available water volume in the Brazilian Northeast. The global ECHAM 4.5 climate model was used to feed the RAMS regional climate model for the Alto Jaguaribe hydrographic basin. Resulting precipitation values were calibrated by the probability density function (PDF) correction of simulated data compared with average daily precipitation data using the Thiessen method for the period 1979-2009. The Heidke Skill Score (HSS) was used to evaluate model performance in the Maximum Predictable Time Interval (ITEMP) of the atmospheric model. These PDF-corrected precipitation data, both observed and RAMS-simulated, were inserted in the hydrologic Soil Moisture Account (SMA) model from the Hydrologic Engineering Center â Hydrologic Modeling System (HEC-HMS) to determine modeled flows. These flows were then compared with median observed flows. To calibrate and validate the SMA, an iterative method was used to minimize percentage error of volume. The data returned by this cascade model was applied to assisting policy-makers determine water releases from the OrÃs reservoir. Three different scenarios were compared, the first based on observed flows, the second flows simulated by SMA with observed precipitation, and the third by flows simulated by SMA driven by the RAMS-PDF precipitation data. The RAMS model showed optimal efficiency in precipitation prediction on a 30 to 45 day interval, with HSS values of 0.56. The SMA model showed satisfactory performance with Nash-Sutcliffe values of 0.89 in the calibration phase and 0.67 in the validation phase, demonstrating its capacity to assist hydrological modeling in the semi-arid. This cascade model showed potential in accurately representing median inflows for the reservoir and as such can be used as a hydrologic tool, assisting reservoir operation decisions to meet the regionâs demand. Keywords: Soil Moisture Account; hydrologic / O presente trabalho visa o acoplamento de modelo atmosfÃrico, hidrolÃgico e de operaÃÃo de reservatÃrio com vistas à otimizaÃÃo da liberaÃÃo de Ãguas no semiÃrido do nordeste brasileiro. O modelo atmosfÃrico regional RAMS foi forÃado pelo modelo atmosfÃrico global ECHAM 4.5, na bacia hidrogrÃfica do Alto Jaguaribe, e em seguida, aplicada a correÃÃo probability density function (PDF) nos dados simulados e comparado com dados diÃrio de precipitaÃÃo mÃdia observada pelo mÃtodo de Thiessen no perÃodo de 1979-2009. Foi utilizando o Heidke Skill Score (HSS) como mÃtrica principal para avaliar o desempenho da previsÃo em busca do Intervalo de Tempo de MÃxima Previsibilidade (ITEMP) do modelo atmosfÃrico. Os dados de precipitaÃÃes observados e simulados pelo RAMS com correÃÃes PDFs foram inseridos no modelo hidrolÃgico Soil Moisture Account (SMA) do Hydrologic Engineering Center - Hydrologic Modeling System (HEC-HMS), e comparado com as vazÃes mÃdias observadas. Para a calibraÃÃo e validaÃÃo do SMA, foi realizado um mÃtodo interativo para minimizar uma funÃÃo objetivo, com base no erro percentual do volume. Por fim foi desenvolvido e avaliado um modelo de cascata a fim de comparar as decisÃes operacionais de liberaÃÃo do reservatÃrio OrÃs com diferentes cenÃrios com base nas vazÃes observadas, vazÃes simuladas pelo SMA com a precipitaÃÃo observada e vazÃes simuladas pelo SMA forÃada com o RAMS-PDF. O modelo RAMS mostrou melhor eficiÃncia na previsÃo da precipitaÃÃo no intervalo de 30 a 45 dias, com valores de HSS = 0,56. O modelo SMA mostrou desempenho satisfatÃrio com valores de Nash-Sutcliffe de 0,89 na fase de calibraÃÃo e 0,67 na fase de validaÃÃo, mostrando ser uma nova alternativa de utilizaÃÃo de modelo hidrolÃgico no semiÃrido. O modelo de cascata mostrou potencial em representar bem as afluÃncias mÃdias do reservatÃrio, podendo tornar uma ferramenta hidrolÃgica, auxiliando as decisÃes de operaÃÃo dos reservatÃrios, atendendo as demandas da regiÃo.

A cultura do feijão (Phaseolus vulgaris L.) apresenta posição de destaque no agronegócio brasileiro e na alimentação da população; a manutenção de elevados índices produtivos está condicionada a utilização da irrigação de forma racional e na escolha adequada das cultivares. Diante disso, torna-se fundamental o conhecimento das respostas fisiológicas e produtiva de diferentes cultivares de feijão submetida a três níveis de disponibilidade hídrica. Tais conhecimentos ainda são pouco difundidos e necessitam de pesquisas para sua melhor compreensão. O objetivo do presente trabalho foi estudar a resposta dos aspectos produtivos e fisiológicos de cultivares de feijão com monitoramento e manejo da irrigação diferenciados. O experimento foi conduzido em condições controladas no Instituto Agronômico do Paraná (IAPAR), em Londrina, PR com delineamento de blocos ao acaso em esquema fatorial e cinco repetições, constando de três cultivares de feijão e três níveis de disponibilidade hídrica no solo, monitorada por tensiômetro instalado a 0,15; 0,20 e 0,30 m de profundidade. Foram avaliados a fitomassa seca das folhas, caule, legume, parte aérea, raízes e total; rendimento de grãos e índice de colheita; fotossíntese, concentração interna de carbono no mesófilo foliar, transpiração e condutância estomática, eficiência da fotossíntese, e eficiência no uso da água instantânea e extrínseca. Os resultados indicaram variação em relação à produção de fitomassa seca de folhas, parte aérea, total, rendimento de grãos e índice de colheita, com maiores valores para a cultivar IAPAR 81 submetida à disponibilidade hídrica total de 463 mm. A cultivar IPR Tangará apresentou resultado semelhante para característica índice de colheita, nas demais não apresentou diferença com disponibilidade hídrica total de 463 e 547 mm, considerando as características citadas anteriormente. Todas as características avaliadas foram menores para a cultivar IPR Curió, a qual não apresentou diferenças com disponibilidade hídrica total de 329 e 404 mm na produção de fitomassa seca da parte aérea, total, rendimento de grãos e índice de colheita. O desenvolvimento radicular das cultivares IAPAR 81 e IPR Tangará foram semelhantes, diferentemente da cultivar IPR Curió que apresentou menor crescimento. Houve comportamento diferenciado das três cultivares avaliadas e maior capacidade de recuperação das atividades fisiológicas para as cultivares IAPAR 81 e IPR Tangará em comparação a cultivar IPR Curió; aos 62 dias após a semeadura, foi observada maior redução nos tratamentos cujo monitoramento da irrigação foi realizado a 0,30 m de profundidade para as cultivares IAPAR 81 e IPR Tangará. A cultivar IPR Curió apresentou redução gradativa dessas características ao longo do ciclo de desenvolvimento. Considerando os resultados conclui-se que as cultivares de feijão apresentaram resposta diferenciada em relação às características produtivas e fisiológicas, a maior produção de grãos ocorreu com disponibilidade hídrica monitorada a 0,20 e 0,30 m de profunidade, as cultivares IAPAR 81 e IPR Tangará apresentaram capacidade de recuperação das atividades fisiológicas após um período de maior estresse; a cultivar IPR Curió apresentou menor eficiência no uso da água. A cultivar IAPAR 81 é mais adequada para locais sujeitos à deficiência hídrica e as cultivares IPR Tangará e IPR Curió serão mais responsivas em sistemas de produção irrigados; não foram observadas alterações nocivas ao aparato fotossintético das cultivares, em função dos tratamentos. / The bean crop (Phaseolus vulgaris L.) has a prominent position in the Brazilian agribusiness and food of the population; the maintaining of high production rates is dependent upon use of irrigation rationally and in choosing suitable of cultivars. Therefore, it is necessary to know the physiological and productive responses of bean cultivars under three levels of water availability. Such knowledge is still not disseminated and need research for better understanding. The aim of this work was to study the response of productive and physiological aspects of bean cultivars with different monitoring and management of irrigation. The experiment was conducted in Agronomic Institute of Paraná State (IAPAR) in Londrina, PR with a randomized block design in a factorial arrangement with five replications, consisting of three bean cultivars and three levels of soil water availability, monitored by tensiometer installed 0.15; 0.20 and 0.30 m depth. Were evaluated: dry biomass of leaves, stems, pod, aerial part, shoots, and total; grain yield and harvest index; photosynthesis, internal carbon concentration in mesophyll, transpiration, stomatal conductance, photosynthesis efficiency, and efficiency in the use of instant and extrinsic water. The results indicated variation in relation to dry biomass production of leaves, aerial part, total, grain yield and harvest index, with higher values for IAPAR 81 cultivar with total water availability of 463 mm. The IPR Tangará cultivar showed similar results of characteristics to harvest index but in the other characteristics showed no difference in total water availability of 463 and 547 mm, considering the characteristics previously mentioned. All characteristics were smaller to IPR Curió cultivar, which no showed differences in total water availability of 329 and 404 mm in the dry biomass production of aerial parts, total grain yield and harvest index. The root development of the IAPAR 81 and IPR Tangará were similar, unlike IPR Curió cultivar which showed lower growth. There was a differential behavior of the three cultivars and greater resilience of physiological activities for IAPAR 81 and IPR Tangará cultivars compared to IPR Curió cultivar; at 62 days after seedling, greater reduction in irrigation treatments whose monitoring was carried out at 0.30 m depth for IAPAR 81 and IPR Tangará cultivars was observed. The IPR Curió cultivar showed gradual reduction of these characteristics throughout the development cycle. Considering the results it is concluded that the cultivars showed different responses in relation to the productive and physiological characteristics, the largest grain production occurred with water availability monitored at 0.20 and 0.30 m depth, the IAPAR 81 cultivars and IPR Tangará showed resilience of physiological activity after a period of increased stress; IPR Curió cultivar showed lower water efficiency use. The IAPAR 81 cultivar is more suitable for locations where the water deficit is frequent and the IPR Tangará and IPR Curió cultivars be more responsive in irrigation systems production; no changes harmful was observed to the photosynthetic apparatus of cultivars, independent of the treatments.

Durante o verão austral, diversas regiões do Brasil, como a Sudeste, porções das Regiões Sul e Nordeste e o Brasil central, sofrem períodos de intensa precipitação, geralmente associados à Zona de Convergência do Atlântico Sul (ZCAS), o que ocasiona sérios problemas econômicos e sociais nessas regiões. Assim, o objetivo geral deste trabalho foi estudar as principais características da ZCAS, sendo que, do ponto de vista de modelagem numérica, pretendeu-se estudar as influências da temperatura da superfície do mar (TSM) e da umidade do solo (US) principalmente na precipitação associada ao sistema. Esse estudo foi realizado através de simulações com o modelo regional BRAMS (Regional Atmospheric Modeling System with Brazilian Developments), para dois casos de ZCAS, ocorridos em 1998 e 1999, períodos, respectivamente, com TSMs do Pacífico leste e central anomalamente quentes (El Niño) e anomalamente frias (La Niña). Através de índices estatísticos foi verificado o desempenho do modelo, usando TSMs com resoluções espaciais e temporais diferentes, na previsão de precipitação nas regiões que compõem a ZCAS (oceânica, costeira e amazônica). O pior e o melhor desempenhos do modelo BRAMS se deram quando do uso de TSMs com resoluções espacial e temporal menos e mais refinadas, respectivamente, para o caso de ZCAS de 1998. Para o caso de 1999 não foram observadas diferenças significativas no desempenho do modelo. Grande parte do erro do modelo na previsão de chuva é devida ao viés do próprio modelo, que é melhor em identificar a ocorrência/não-ocorrência de chuva do que em localizar núcleos mais intensos. No entanto, o BRAMS apresenta alto skill no que se refere à quantidade de chuva. Com respeito à simulação de precipitação nas regiões que compõem a ZCAS, o melhor e o pior desempenhos do modelo se deram nas regiões amazônica e oceânica, respectivamente. Com relação à US verificaram-se as influências da condição de solo mais seca possível, aplicada às regiões de ZCAS continental, em características do sistema como convergência de umidade e precipitação. De maneira geral, a quantidade de precipitação acumulada nas regiões onde se aplicou a condição seca foi maior do que no experimento controle devido à convergência de umidade, que é transportada das regiões circunvizinhas para a região de solo mais seco por circulações de meso e grande escalas geradas por heterogeneidades na superfície. Analisaram-se ainda diferenças nas características da ZCAS observada e simulada em diferentes fases do El Niño-Oscilação Sul (ENOS). Os casos de ZCAS de 1998 e 1999 se apresentaram mais alongado sobre o Atlântico e predominantemente continental, respectivamente, o que confirma que períodos de El Niño (La Niña) favorecem a ocorrência de ZCAS oceânica (continental). Nos testes de sensibilidade do BRAMS à US foi observado provável efeito do ENOS sobre a ZCAS simulada, uma vez que o movimento ascendente na ZCAS amazônica foi menos intenso do que na costeira em 1998, ocorrendo o oposto em 1999. A fase quente (fria) do ENOS favorece a subsidência (ascendência) na região amazônica, podendo ter contribuído para enfraquecer (intensificar) o movimento vertical nessa região em 1998 (1999). / During austral summer, several regions of Brazil, as Southeast, portions of South and Northeast Regions and central Brazil, suffer periods of intense precipitation, generally associated with South Atlantic Convergence Zone (SACZ), which causes serious economic and social problems in those regions. Notwithstanding, the general objective of this work was to study the main features of SACZ, and in terms of numerical modeling, it intended to study the influences of the sea surface temperature (SST) and of the soil moisture (SM) mainly upon the precipitation associated with the system. This study was carried out through simulations with BRAMS (Regional Atmospheric Modeling System with Brazilian Developments) regional model, to two SACZ cases, occurred in 1998 and in 1999, periods, respectively, with SSTs of Eastern and central Pacific abnormally warm (El Niño) and abnormally cold (La Niña). Through statistical indices it was verified the model performance, using SSTs with different spatial and temporal resolutions, upon the precipitations forecasting in the regions that compound SACZ (oceanic, coastal and Amazon). The worst and the best performances of BRAMS model occurred when using SST\'s with less and more refined spatial and temporal resolutions, respectively, to the SACZ case of 1998. To the case of 1999 it was observed no significant differences in the models performance. Much of the models error in rains forecasting is due to the bias of the model itself, which is better in identifying the occurrence/non-occurrence of rain than in locate more intense nuclei. However, the BRAMS has high skill regarding to the amount of rain. About the precipitations simulation in the regions that compound SACZ, the best and the worst models performances occurred in the Amazon and oceanic regions, respectively. Concerning the SM it was verified the influences of the driest possible soil condition, applied to continental regions of SACZ, upon systems features such as moisture convergence and precipitation. In general, the amount of rainfall in regions where the dry condition was applied was higher than in the control experiment due to the moisture convergence, which is transported from surrounding regions to the one of drier soil by meso and large scale circulations generated by heterogeneities on the surface. It was also analyzed differences in the characteristics of observed and simulated SACZ at different phases of El Niño-Southern Oscillation (ENSO). The SACZ cases of 1998 and of 1999 were presented more elongated over the Atlantic and predominantly continental, respectively, confirming that periods of El Niño (La Niña) favor the occurrence of oceanic (continental) SACZ. In the BRAMS sensibility tests to SM it was observed probable effect of ENSO upon simulated SACZ, as the upward motion in Amazon SACZ was less intense than in the coastal one in 1998, occurring the opposite in 1999. The warm phase of ENSO favors the subsidence (rising) on Amazon region, which may have contributed to weaken (intensify) the vertical motion on the region in 1998 (1999).

Praticamente toda cana-de-açúcar produzida no Estado de São Paulo é cultivada em condições de sequeiro e o aproveitamento de novas áreas para a sua produção, nas quais haja necessidade de drenagem, torna-se importante. O dimensionamento de sistemas de drenagem agrícola baseado apenas na experiência prática do projetista tem levado a freqüentes insucessos. Para o dimensionamento racional, é necessário se conhecer a velocidade mínima de rebaixamento do lençol freático a ser proporcionado pelos drenos, o que depende da sensibilidade de cada cultura. Assim, este trabalho tem como objetivos determinar o efeito de diferentes velocidades de rebaixamento do NF, em diferentes estádios de desenvolvimento da cana-de-açúcar. O experimento foi conduzido em 64 lisímetros, em um delineamento experimental de blocos casualizados, arranjado em um fatorial de (3 x 5 + 1), sendo 3 estádios de desenvolvimento, 5 velocidades de rebaixamento do NF mais uma testemunha que não sofrerá estresse por excesso de umidade. Os resultados obtidos permitiram a obtenção de um critério de drenagem para o cálculo do espaçamento de drenos utilizando equações de movimento não permanente. A produtividade e seus componentes expressos em valores médios de massa verde de colmos, massa seca dos colmos, massa verde dos ponteiros, massa seca dos ponteiros, massa verde total e massa seca total não foram afetados pelas velocidades de rebaixamento de 0,30 m em 3, 6, 9, 12 e 15 dias. Entre os índices fisiológicos avaliados a condição de inundação das parcelas proporcionada pelas diferentes velocidades de rebaixamento do NF não interferiu nos valores médios da taxa de crescimento absoluto, taxa de assimilação liquida e na taxa de crescimento da cultura. Já a razão de área foliar, a taxa de crescimento relativo, e área foliar especifica apresentaram diferenças significativas para os períodos. O valor médio de Brix obtidos nas plantas que sofreram estresse pelo encharcamento no período de 305 DAP sob uma velocidade rebaixamento de 0,30 m em 12 dias apresentou valor médio de 16,03 % de brix, inferior e significativamente diferente dos demais períodos e velocidades. As parcelas inundadas aos 67 dias após o plantio apresentaram valores de pH no solo superiores aos demais períodos 210 e 305. Os valores médios de potenciais de oxiredução aumentam a medida que reduz o teor de umidade do solo. Os valores médios de oxigênio dissolvido aumentaram ao longo dos períodos de avaliação. Ocorreu uma redução e estabilização nos valores médios das leituras com o decorrer dos dias de avaliação. Em experimentos onde se tem uma limitação de material é possível utilizar uma mesma folha da canade- açúcar para determinar o potencial de água na folha. No entanto há a necessidade de proteger o local da fração foliar destacada com um papel alumínio. Os valores médios de potencial de água na folhas não se apresentaram diferentes estatisticamente entre as parcelas submetidas à inundação, assim como, quando comparados as parcelas sob irrigação. A severidade dos cincos velocidades de rebaixamentos não refletiu nos teores dos macronutrientes na folhas das plantas. / Almost all sugar cane produced in the State of Sao Paulo is grown under rainfed conditions and the exploration of new cultivated areas, were there is a need for drainage, becomes important. The design of agricultural drainage systems based only on practical experience of the designer has led to frequent failures. For the rational sizing, it is necessary to know the minimum speed of lowering the water table to be provided by the drains, which depends on the sensitivity of each crop. Thus, this study aims to determine the effect of different speeds of lowering the water table, at different development stages of sugar cane. The experiment was conducted in 64 lysimeters in a randomized blocks design, arranged in a factorial of (3 x 5 + 1), of three development stages, five speed of lowering the water table and a control that did not suffer stress by excess moisture. The results enabled to obtain a criteria of drainage for calculating the spacing of drains using no permanent motion equations. The yield and its components expressed in average values of green mass of stalks, dry weight of stalks, green mass of top, top of dry mass, total mass green and total dry mass were not affected by lowering speeds of 0,30 m 3, 6, 9, 12 and 15 days, no differences between them and not the control. Among the avaliated physiological indexes the flood condition of the plots provided by the different speeds of lowering of the water table did not interfere in the average values of absolute growth rate, net assimilation rate and growth rate of the crop. Whereas the leaf area ratio, the relative growth rate and specific leaf area showed significant differences for the periods. The average value of Brix obtained in plants that have suffered stress by flooding in the period of 305 DAP under lowering a speed of 0,30 m in 12 days showed a mean value of 16,03% of Brix, and significantly different than the other periods and speeds. The plots flooded for 67 days after planting showed pH values in soil higher than other periods 210 and 305. The average values of potential oxiredution increase with the reduction of the moisture content of soil. The average values of dissolved oxygen increased over the evaluation periods. And a reduction and stabilization in the average of the readings over the course of days evaluation. In experiments where there is a limitation of material one can use a single leaf sheet of sugar cane to determine the potential of water on the sheet. However there is a need to protect the site of the fraction leaf with an aluminum sheet. The average values of water potential in leaves did not show statistically different between plots subjected to flooding as well as, when compared to plots under irrigation. The severity of the five speeds, did not reflected in lower levels of macronutrients in the plant leaves.