The increasing human population, industrialization, urbanisation and climate change challenges have resulted in an increased demand for already scarce water resources. This has left the agricultural sector with less water for production. Sustainable water management strategies would therefore require accurate determination of water-use. In agriculture, water-use can best be determined from total evaporation which is the loss of water from soil and vegetation to the atmosphere. Accurate quantification of total evaporation from vegetation would require a thorough understanding of water transport processes between vegetation and the atmosphere, especially in a water-scarce country like South Africa. Several methods for estimating total evaporation have been developed and are in use today. Some of the common methods used today are: the Bowen ratio energy balance, eddy covariance, scintillometry, flux variance and surface renewal. However, various methods have advantages and disadvantages. Considerations include the cost of equipment and level of skill required for use of some of the methods. A number of methods involve indirect or direct estimation of sensible heat flux then calculating latent energy flux and hence total evaporation as a residual of the shortened energy balance equation. The main objective of this study is to determine the effects of grassland management practices on the energy balance components as well as on the surface radiation balance. Eddy covariance and surface renewal methods were employed to investigate the effects of grassland management practices (mowing and burning) on the micrometeorology of naturally occurring grassland. A 4.5-ha grassland site (Ukulinga, Pietermaritzburg, South Africa) was divided into two halves: one area was initially mowed (cut-grass site) to a height of 0.1 m while the other was not mowed (tall-grass site). The tall-grass site was later treated by burning and hence referred to as the burnt-grass site. Two eddy covariance systems were deployed, one at each of the cut-grass and the tall-grass sites. The systems each comprised a three-dimensional sonic anemometer to measure high frequency sonic temperature, orthogonal wind speeds and directions and the eddy covariance sensible heat flux (W m-2). Latent energy flux, from which total evaporation was then determined, was calculated as a residual from the shortened energy balance equation from measurements of sensible heat flux, net irradiance and soil heat flux assuming closure is met. Other microclimatic measurements of soil water content, soil temperature, surface reflection coefficient and reflected solar irradiance were performed, the latter with a four-component net radiometer. An automatic weather station was also set up at the research site for continuous measurements of solar irradiance, air temperature, relative humidity, wind speed and direction and rainfall. Water vapour pressure and grass reference evaporation were also determined online. Energy fluxes from the tall-grass site were measured from March to June 2008. Greater total evaporation rates (2.27 mm day-1) were observed at the beginning of the experiment (March). As winter approached most of the energy balance components showed a constant decreasing trend and the average total evaporation rates for May and June were 1.03 and 0.62 mm day-1, respectively. The tall-grass site had consistently lower soil temperatures that changed diurnally when compared to the cut-grass site. The soil water content at both sites showed no significant differences. Most of the energy balance components were similar between the two sites and changed diurnally. Although there were small differences observed between other energy balance components, for example, latent energy flux was slightly greater for the tall-grass site than for the cut-grass site. The tall-grass site had more basal cover and this may have contributed to the differences in temperature regimes observed between the two sites. However, the plants growing at the cut-grass site showed more vigour than the ones at the tall-grass site as spring approached. Burning of a mixed grassland surface caused significant changes to most of the optical properties and energy fluxes of the surface. Following burning, the soil temperature was elevated to noticeable levels due to removal of basal cover by burning. The surface reflection coefficient measured before and after the burn also presented a remarkable change. The surface reflection coefficient was significantly reduced after the burn but a progressive increase was observed as the burnt grass recovered after the spell of spring rains. The energy fluxes: net irradiance, latent energy flux and soil heat flux also increased following the burn but the latent energy flux was reduced as transpiration was effectively eliminated by the burning of all actively transpiring leaves. As a result, the main process that contributed towards latent energy flux was soil evaporation. An ideal surface renewal analysis model based on two air temperature structure functions was used to estimate sensible heat flux over natural grassland treated by mowing. Two air temperature lag times r (0.4 and 0.8 s) were used when computing the air temperature structure functions online. The surface renewal sensible heat fluxes were computed using an iteration process in Excel. The fluxes, obtained using an iterative procedure, were calibrated to determine the surface renewal weighting factor (a) and then validated against the eddy covariance method using different data sets for unstable conditions during 2008. The latent energy flux was computed as a residual from the shortened energy balance equation. The surface renewal weighting factor was determined for each of the two heights and two lag times for each measurement height (z) above the soil surface. The a values obtained during the surface renewal calibration period (day of year 223 to 242, 2008) ranged from 1.90 to 2.26 for measurement height 0.7 m and r = 0.4 and 0.8 s. For a measurement height of 1.2 m and r = 0.4 and 0.8 s, a values of 0.71 and 1.01 were obtained, respectively. Good agreement between surface renewal sensible heat flux and eddy covariance sensible heat flux was obtained at a height of 1.2 m using a = 0.71 and a lag time of 0.4 s. Total evaporation for the surface renewal method was compared against the eddy covariance method. The surface renewal method, for a height of 1.2 m and a lag time of 0.4 s, yielded 1.67 mm while the eddy covariance method yielded 1.57 mm for a typical cloudless day. For the same day for a measurement height of 1.2 m and a lag time of 0.8 s, eddy covariance and surface renewal methods yielded 1.57 and 1.10 mm, respectively. For a lag time of 0.4 s, the surface renewal method overestimated total evaporation by 0.10 mm while for a lag time of 0.8 s, the total evaporation was underestimated by 0.47 mm. As a result, the surface renewal method performed better for z = 1.2 m and a lag time of 0.4 s. The eddy covariance method gave reliable sensible heat fluxes throughout the experiment and this allowed a comparison of fluxes across all treatment areas to be achieved. The short-term analysis of the surface renewal method also gave reliable energy fluxes after calibration. Compared to the eddy covariance method, the surface renewal method is more attractive in the sense that it is easy to operate and use and it is relatively cheap. However, the surface renewal method requires calibration and validation against a standard method such as the eddy covariance method. This study showed that grassland management practices had a considerable effect on surface radiation and energy balance of the mowed and burnt treatment sites. Total evaporation was mainly controlled by the available energy flux, rainfall and grassland surface structure. High total evaporation values were observed during summer when net irradiance was at its highest and grass growth at its peak. Low total evaporation values were observed in winter (dry atmospheric conditions) when net irradiance was at its lowest and most vegetation was dormant. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

[Truncated abstract] In the most common (hydrological) viewpoint, vegetation is a

A vegetação tropical é uma das maiores fontes de evapotranspiração e desempenha um papel importante na dinâmica climática global e nos processos de produtividade primária de ecossistemas terrestres, uma vez que se encontra diretamente ligada aos processos de transferência de massa e energia. Objetivou-se nesta tese de doutorado avaliar a acurácia das estimativas de ET baseadas em modelos de sensoriamento remoto quando comparadas a medições pontuais obtidas a partir de torres de fluxo e a partir do fechamento do balanço hídrico a médio e longo prazo. Foram selecionados dois modelos: para escalas locais e regionais usou-se o algoritmo SEBAL, enquanto que para escalas continentais e globais utilizou-se o algoritmo MOD16. Em relação ao algoritmo SEBAL, a metodologia empregada apresentou bons resultados tanto nas estimativas pontuais dos fluxos de calor latente quanto em relação ao fechamento do balanço hídrico em grandes áreas. Em relação ao algoritmo MOD16, verificou-se que as estimativas de evapotranspiração apresentam melhores resultados a longo prazo e em grandes áreas. As análises aqui realizadas sugerem que os algoritmos SEBAL e MOD16 podem capturar razoavelmente bem as respostas da vegetação em relação à variabilidade espacial e temporal em larga escala. Considerando que esses algoritmos podem ser aplicados desde escalas regionais até escalas globais, os resultados estão em um intervalo aceitável de acurácia, indicando um potencial significativo no monitoramento espacial e temporal do processo de ET de forma contínua e sistemática a partir de informações obtidas por sensoriamento remoto. / Tropical vegetation is a major source of global land surface evapotranspiration (ET) and plays an important role in the global climate dynamics and in the processes of primary production of terrestrial ecosystems, since it is directly linked to the mass transfer and energy balance. The aim of this doctoral thesis was to evaluate the accuracy of ET estimates based on remote sensing models when compared to measurements obtained from flux towers and hydrological models. Two algorithms were selected: for local and regional scales SEBAL was used, while for continental and global scales, MOD16 was adopted. Regarding SEBAL algorithm, the applied methodology showed that significant results were achieved in both latent heat flux and water balance over large areas. Concerning MOD16 algorithm, the research suggested that evapotranspiration estimates showed better results in the long-term and in large areas. The analysis suggests that MOD16 and SEBAL algorithms can capture reasonably well the responses of vegetation in relation to spatial and temporal variability on a large scale. Taking into consideration that these algorithms can be applied from regional to global scales, the results are in an acceptable range of accuracy, indicating a significant potential for monitoring evapotranspiration using remote sensing data.

Made available in DSpace on 2016-08-31T13:24:16Z (GMT). No. of bitstreams: 1 WesleyOS_DISSERT.pdf: 2112075 bytes, checksum: e031debdc03a494ea8ff5b742a678f1a (MD5) Previous issue date: 2014-07-06 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The culture of maize (Zea mays L.) has great importance for economic and social order in Brazil, due to its high productivity, nutritional value and the numerous uses in food and feed, fresh and high-tech industry. The cultivation of maize for the production of corn is increased significantly because of profitability, as in the form of green beans, the commercial value is larger as compared to corn in the form of dry grains. The water requirement of maize is variable depending on the prevailing climatic factors during development, variety and stage of culture. If there is one week after water stress anthers arise, there may be a 50% drop in its production, so this study aimed to determine the crop evapotranspiration (ETc) and crop coefficients (Kc) for different stages of development of corn hybrid AG 1051, to evaluate the growth and development and productivity, and economic analysis of corn grown in double rows (1.3 x 0.2 x 0.2 m) under drip irrigation in the community in Alagoinha Mossoró/RN. The measurement was performed daily ETc was used four weighing lysimeters, with an area of 2.25 m2 (dimensions 1.5 x 1.5 m in area and 1 m deep) was performed for monitoring of moisture soil through eight TDR probes (6 merits of Campbell and two built by hand at depths of 0-30 cm and 15-45 cm in the lysimeters installed and planting area. Reference evapotranspiration (ETo) was estimated by method Penman-Monteith-FAO. The crop cycle was 77 days and the total ETo and ETc during this period were 334.90 and 300.54 mm, respectively. Phonological phases were set at 16, 20, 27 and 14 days for initial phase (Phase I), the vegetative development (Phase II) flowering (phase III) and physiological maturation (phase IV), respectively. Crop coefficients obtained for the various stages of development were 0.50, 0.64 , 1.12 and 1.11 for the respective phases I, II, III and IV. Kc values obtained were close to those recommended by the FAO-56 for the corn crop. During the crop cycle, the maximum height of plants were 2.38 m, and the average height corresponding to 1.2 m, the average number of sheets was 14, the average diameter of the crown was 48.28 cm and 81.00 cm maximum corresponding to the plants on single row, double row now for the average diameter of the crown was 98.56 cm and the maximum corresponding to 1.78 m. The average yield for corn (cob with husk) was 12.239 kg ha-1 grain, while for (marketable husked ear) was 6.380 kg ha-1 and grain yield obtained was approximately 5581 kg ha-1. According to the receipts additional/extra cost, it appears that in the case of the practice of harvesting corn ( production system adopted as a reference), each real invested in additional cost, generates $ 59.84 of additional revenue / A cultura do milho (Zea mays L.) apresenta grande importância de ordem econômica e social no Brasil, devido, sua elevada produtividade, valor nutritivo e pelas diversas formas de utilização na alimentação humana e animal, in natura e na indústria de alta tecnologia. O cultivo de milho destinado à produção de milho verde vem aumentado de forma significativa, em função de sua lucratividade, pois na forma de grãos verdes, o valor de comercialização é maior, quando comparado com o milho na forma de grãos secos. A exigência hídrica do milho é variável, dependendo dos fatores climáticos reinantes no período de desenvolvimento, da variedade e do estádio da cultura. Se houver deficiência hídrica uma semana após surgirem anteras, pode ocorrer uma queda de 50% na sua produção, com isso este trabalho teve por objetivo determinar a evapotranspiração da cultura (ETc) e os coeficientes de cultivo (Kc) para os diferentes estádios de desenvolvimento da cultura do milho híbrido AG 1051, avaliar o crescimento e o desenvolvimento bem como a produtividade, além da análise econômica do milho cultivado em fileira dupla (1,3 x 0,2 x 0,2 m) irrigado por gotejamento na comunidade de Alagoinha em Mossoró/RN. A medição da ETc diária foi realizada utilizado-se quatro lisímetros de pesagem, com área útil de 2,25 m2 (dimensões de 1,5 x 1,5 m de área e 1 m de profundidade), foi realizado o monitoramento da umidade do solo por meio de oito sondas TDR (6 de procedência da Campbell e duas construídas artesanalmente nas profundidades de 0-30 cm e de 15-45 cm instaladas nos lisímetros e na área de plantio. A evapotranspiração de referência (ETo) foi estimada pelo método Penman-Monteith-FAO. O ciclo da cultura foi de 77 dias e a ETo e ETc total durante esse período foram de 334,90 e 300,54 mm, respectivamente. As fases fonológicas ficaram definidas em 16, 20, 27 e 14 dias para a fases inicial (Fase I), de desenvolvimento vegetativo (Fase II), floração (Fase III) e maturação fisiológica (Fase IV), respectivamente. Os coeficientes de cultivo obtidos para os diferentes estádios de desenvolvimento foram de 0,50; 0,64; 1,12 e 1,11 para as respectivas fases I, II, III e IV. Os valores de Kc obtidos ficaram próximos aos recomendados pela FAO-56, para a cultura do milho. Durante o ciclo da cultura, a altura máxima das plantas foi de 2,38 m, sendo que a altura média correspondeu a 1,2 m, o número médio de folhas foi 14, o diâmetro médio da copa foi 48,28 cm e o máximo correspondeu a 81,00 cm para as plantas na fileira simples, já para a fileira dupla o diâmetro médio da copa foi 98,56 cm e o máximo correspondeu a 1,78 m. A produtividade média para milho verde (espigas empalhadas comercializáveis) foi de 12.239 grãos kg ha-1, já para (espigas despalhadas comercializáveis) foi de 6.380 kg ha-1 e para grãos a produção obtida foi de aproximadamente 5.581 kg ha-1. De acordo com razão receita adicional/custo adicional, verifica-se que no caso da prática de colheita de milho verde (sistema de produção adotado como referência), cada real aplicado no custo adicional, gera R$ 59,84 de receita adicional

Made available in DSpace on 2016-08-31T13:24:18Z (GMT). No. of bitstreams: 1 PauloSS_DISSERT.pdf: 270618 bytes, checksum: 01f46ee88e3f016cd7af1461882aabc4 (MD5) Previous issue date: 2008-12-29 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / The study was conducted at the Experimental Farm Rafael Fernandes, Mossoró city, Rio Grande do Norte State, Brazil, with the objective to verify the effect of irrigation levels and planting densities on the castor bean production, BRS ENERGIA . Thus, we used the experimental design in randomized blocks in a split-plot 5 x 2, with four replications. The treatments consisted of irrigation levels (0.6, 0.8, 1.0, 1.2 and 1.4 of ETc) in main plots and plant densities in the sub-plots formed by arrangements 1.50 m x 0.30 m x 0.30 m (D1 - 37,037 plants ha-1) and 1.50 m x 0.30 m x 0.40 m (D2 - 27,778 plants ha-1). The main plots were 18 m in length, 9 m for each of the densities. The irrigation levels were differentiated by the application time using the tubes, each of which had a strip of the water distribution system independent. The main bunches fruits income decreased with the applied levels and the secondary bunches income (in fruits and grains) followed quadratic polynomial model. How much to the total income, was gotten 3,974 kg ha-1 of fruits and 2,691 kg ha-1 of grains with irrigation based on 1,20 and 1,25 of the etc, respectively. / O trabalho foi conduzido na Fazenda Experimental Rafael Fernandes, município de Mossoró, RN, com o objetivo verificar o efeito de lâminas de irrigação e densidades de plantio sobre a produção da mamoneira, cultivar BRS ENERGIA . Para tanto, utilizou-se o delineamento experimental em blocos ao acaso, em esquema de parcelas subdivididas 5 x 2, com quatro repetições. Os tratamentos foram constituídos das lâminas de irrigação (0,6; 0,8; 1,0; 1,2; e 1,4 da ETc) nas parcelas principais e as densidades de planta nas sub- parcelas formadas pelos arranjos 1,50 m x 0,30 m x 0,30 m (D1 - 37.037 plantas ha-1) e 1,50 m x 0,30 m x 0,40 m (D2 - 27.778 plantas ha-1). As parcelas principais tinham 18 m de comprimento, sendo 9 m para cada uma das densidades. As lâminas foram diferenciadas através do tempo de aplicação utilizando-se válvulas, sendo que cada uma das lâminas teve um sistema de distribuição de água independente. O rendimento de frutos dos racemos principais decresceu com as lâminas aplicadas e o rendimento dos racemos secundários (em frutos e em grãos) seguiu modelo polinomial quadrático. Quanto ao rendimento total, obteve-se 3.974 kg ha-1 de frutos e 2.691 kg ha-1 de grãos com irrigação baseada em 1,20 e 1,25 da ETc, respectivamente.

Made available in DSpace on 2016-08-31T13:24:19Z (GMT). No. of bitstreams: 1 JoseSS_DISSERT.pdf: 4245347 bytes, checksum: a7b834a7b467424e2273b3e8405fcd27 (MD5) Previous issue date: 2010-08-04 / Water is one of the main factors that limit agricultural yield, consequently reducing the efficiency of crop production. It makes necessary then a special management of irrigation that allows total capacity of production. This way, to implement strategic programs of local or regional development of agriculture based on the availability of water resources it is essential to have a good understanding of crop evapotranspiration on its different stages of development as well as of the quality of the water used in the irrigation process. In the northeast, due to water shortages many farmers are forced to use water containing high levels of salinity what reduces the production in crops with low tolerance to salinity. So, the main objective in this study is to determine the production coefficients during the watermelon production period, in the region of Mossoró city in the State of Rio Grande do Norte, Brazil, and the effect of nitrogen and salinity on watermelon production. Therefore an experiment was carried out in Mossoró city. The experiment was in a randomized block design in which was used a plan of subdivided parts. In these parts it was studied five levels of salinity (S1 = 0,57; S2 = 1,36; S3 = 2,77; S4 = 3,86 e S5 = 4,91 dS m-1) and three levels of nitrogen in subparts (N1 = 48,0; N2 = 96,0 e N3 = 144,0 kg ha-1). For the ETo estimate it was used the Penman Equation Monteith FAO. The meteorological data necessary for this ETo estimate were collected by an agrometeorological automatic weather station, located on the experimental area. The ET was measured by four weighting lisimeters, which covered an area of 3,00 m2 and were installed in blocks 1 and 2, in the salinity levels S1 and S5. The results have demonstrated that the ETc diminished between the irrigation water S1 and S5, and the total evapotranspiration during the cycle was 336,86 and 220,45 mm respectively. It was realized that the average values referring to Kc in the fenological stages I, II, III and IV of 0,15, 0,87, 1,38 and 0,82 for treatment S1 and 0,15, 0,65, 08,3 and 0,51 for treatment S5, demonstrating that the Kc s obtained for level S1 were higher than the ones obtained for level S5, except for stage I. There was an expressive effect of nitrogen on the production components. The total production of fruit for Quetzali cultivar as much as for Shadow cultivar were severely affected by the quality of irrigation water. For the Quetzali cultivar the total production was reduced from 27,12 to 17,06 Mg ha-1. While for the Shadow cultivar it was reduced from 55,45 to 40,80 Mg ha-1, respectively for the salinity levels S1 and S5. / A água é um dos principais fatores que limitam o rendimento da cultura, reduzindo assim a eficiência da produção agrícola. Torna-se necessário então, um manejo adequado da irrigação de modo a permitir a manifestação do seu potencial produtivo. Assim para implantar programas estratégicos de desenvolvimento agrícola local ou regional baseados na disponibilidade de recursos hídricos é de fundamental importância o conhecimento da evapotranspiração da cultura nos seus diferentes estádios de desenvolvimento, bem como a qualidade da água de irrigação. No Nordeste, devido a escassez de água muitos agricultores são obrigados a utilizarem águas com salinidade alta, limitando com isso a produção da cultura. Diante do exposto este trabalho teve como objetivo determinar os coeficientes de cultivo durante o ciclo da cultura da melancia, na região de Mossoró - RN, bem como o efeito do nitrogênio e da salinidade na sua produção. Para tanto, foi realizado um experimento na cidade de Mossoró-RN. O experimento foi delineado em blocos inteiramente casualizados, usando o esquema em parcela subdivididas. Nas parcelas estudou-se cinco níveis de salinidade (S1 = 0,57; S2 = 1,36; S3 = 2,77; S4 = 3,86 e S5 = 4,91 dS m-1) e três níveis de nitrogênio nas subparcelas (N1 = 48,0; N2 = 96,0 e N3 = 144,0 kg ha-1). Para a estimativa da ETo foi utilizada a Equação Penman Monteith FAO. Os dados meteorológicos necessários para a estimativa da ETo foram coletados por uma estação agrometeorológica automática, instalada na área experimental. A ET foi medida em quatro lisímetros de pesagem, que ocupava uma área de 3,00 m2, instalados nos blocos 1 e 2, nos níveis de salinidade S1 e S5. Os resultados mostraram que a ETc diminuiu entre a água de irrigação S1 e S5, onde a evapotranspiração total durante o ciclo foi de 336,86 e 220,45 mm, respectivamente. Quanto aos Kc s verificaram-se os valores médios nos estádios fenológicos I, II, III e IV, de 0,15, 0,87, 1,38 e 0,82 para o tratamento S1 e 0,15, 0,65, 0,83 e 0,51 para o tratamento S5, mostrando que os Kc s obtidos para o nível S1 foram sempre maiores que os Kc s obtidos para o nível S5, excetuando-se a fase I. Não houve efeito significativo do nitrogênio sobre os componentes de produção. A produção total de frutos tanto para cultivar Quetzali quanto para a Shadow foram significativamente afetados pela qualidade da água de irrigação. Havendo uma redução linear da produtividade à medida que a salinidade da água de irrigação aumentou. Para a Quetzali a produtividade reduziu de 27,12 para 17,06 Mg ha-1 ; enquanto que para Shadow foi de 55,45 para 40,80 Mg ha-1, respectivamente para os níveis de salinidade S1 e S5.

A vegetação tropical é uma das maiores fontes de evapotranspiração e desempenha um papel importante na dinâmica climática global e nos processos de produtividade primária de ecossistemas terrestres, uma vez que se encontra diretamente ligada aos processos de transferência de massa e energia. Objetivou-se nesta tese de doutorado avaliar a acurácia das estimativas de ET baseadas em modelos de sensoriamento remoto quando comparadas a medições pontuais obtidas a partir de torres de fluxo e a partir do fechamento do balanço hídrico a médio e longo prazo. Foram selecionados dois modelos: para escalas locais e regionais usou-se o algoritmo SEBAL, enquanto que para escalas continentais e globais utilizou-se o algoritmo MOD16. Em relação ao algoritmo SEBAL, a metodologia empregada apresentou bons resultados tanto nas estimativas pontuais dos fluxos de calor latente quanto em relação ao fechamento do balanço hídrico em grandes áreas. Em relação ao algoritmo MOD16, verificou-se que as estimativas de evapotranspiração apresentam melhores resultados a longo prazo e em grandes áreas. As análises aqui realizadas sugerem que os algoritmos SEBAL e MOD16 podem capturar razoavelmente bem as respostas da vegetação em relação à variabilidade espacial e temporal em larga escala. Considerando que esses algoritmos podem ser aplicados desde escalas regionais até escalas globais, os resultados estão em um intervalo aceitável de acurácia, indicando um potencial significativo no monitoramento espacial e temporal do processo de ET de forma contínua e sistemática a partir de informações obtidas por sensoriamento remoto. / Tropical vegetation is a major source of global land surface evapotranspiration (ET) and plays an important role in the global climate dynamics and in the processes of primary production of terrestrial ecosystems, since it is directly linked to the mass transfer and energy balance. The aim of this doctoral thesis was to evaluate the accuracy of ET estimates based on remote sensing models when compared to measurements obtained from flux towers and hydrological models. Two algorithms were selected: for local and regional scales SEBAL was used, while for continental and global scales, MOD16 was adopted. Regarding SEBAL algorithm, the applied methodology showed that significant results were achieved in both latent heat flux and water balance over large areas. Concerning MOD16 algorithm, the research suggested that evapotranspiration estimates showed better results in the long-term and in large areas. The analysis suggests that MOD16 and SEBAL algorithms can capture reasonably well the responses of vegetation in relation to spatial and temporal variability on a large scale. Taking into consideration that these algorithms can be applied from regional to global scales, the results are in an acceptable range of accuracy, indicating a significant potential for monitoring evapotranspiration using remote sensing data.

SILVA, Eduardo Magno Pereira. Determinação do coeficiente de cultura da melancia, em solo sob palhada e preparo convencional, na microrregião de Teresina, Piauí. 2012. 102 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Centro de Ciências Agrárias, Departamento de Engenharia Agrícola, Fortaleza-CE, 2012. / Submitted by demia Maia (demiamlm@gmail.com) on 2016-06-21T13:35:20Z No. of bitstreams: 1 2012_dis-empsilva.pdf: 2759087 bytes, checksum: d0dfc3464fcc4081ed5b63da1851ebd4 (MD5) / Approved for entry into archive by demia Maia (demiamlm@gmail.com) on 2016-06-21T13:36:15Z (GMT) No. of bitstreams: 1 2012_dis-empsilva.pdf: 2759087 bytes, checksum: d0dfc3464fcc4081ed5b63da1851ebd4 (MD5) / Made available in DSpace on 2016-06-21T13:36:15Z (GMT). No. of bitstreams: 1 2012_dis-empsilva.pdf: 2759087 bytes, checksum: d0dfc3464fcc4081ed5b63da1851ebd4 (MD5) Previous issue date: 2012

Made available in DSpace on 2015-03-26T13:50:18Z (GMT). No. of bitstreams: 1 texto completo.pdf: 478082 bytes, checksum: 5e70d0378d5af63ea956dca05531ef66 (MD5) Previous issue date: 2006-09-21 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Species of the gender Eucalyptus, whose characteristics as fast growth and capacity of resisting to the water stress, they are used in wide climbs in the establishment of industrial forests in several countries, among which ones, highlights Brazil with more than 3 million planted hectares. The tropical and subtropical climate in most of the Brazilian territory allows an uninterrupted growth and, consequently, a fast biomass accumulation. It is known that the growth and the development of the vegetables is consequence of several physiologic processes, which are controlled by the environmental conditions and characteristic genetics of each vegetable species. Therefore, for best to understand the growth, the development and the impact hydrology of an eucalyptus plantation, it is done necessary to know the factors that control the use of the water. Several environmental factors influence the opening and the closing stomatic, determining larger or smaller transfer of water vapour for the atmosphere. Among these, they highlight the levels of humidity of the soil, the tenor of humidity of the air, solar radiation, temperature of the air and vapour pressure deficit. Specifically, plants with initial age of development present discontinuity in the covering of the soil, being these subject isolated plants the largest interaction with the atmosphere, tending to present larger exhibition of the canopy to the wind and the solar radiation, for that, the given aerodynamic treatment the those plants should be different in relation to plants in adult age, with total covering of the soil. Usually, the growth models consider in the estimate of the conductance of surface of the water vapour the canopy as a leaf big, only and continuous (theory of "Big Leaf"). This approach is not adapted in the initial stage of development of forests. This age in relation to the another have a great importance, once in that period the plants present larger growth rate, once the biomass earnings is directly related to the evapotranspiration processes (loss of water vapour) and photosynthesis (earnings of CO2). In this context, the objective of this study was to model the evapotranspiration for eucalyptus plants in initial phase of development. The experimental site is located in an area belonging to Aracruz Celulose in city of Aracruz, state of Espírito Santo. The meteorological data, solar radiation, temperature of the air, relative humidity, speed of the wind and precipitation were collected in a tower of 38 m of located height among four trees. The methodology used in the modelling of the evapotranspiration was based in the work of Angelocci (1996), when the same in his study made estimates for the evapotranspiration of apple trees in orchards. For the comparison of the results, he esteemed the evapotranspiration by the method of the Bowen Ration for being this a method that describes the relationship soil-plant- atmosphere well. After the analysis of the results for the whole studied period, it verified that to the initial stage of development of the eucalyptus, the developed model showed efficient in the estimate of the evapotranspiration. / Espécies do gênero Eucalyptus, cujas características como crescimento rápido e capacidade de resistir ao estresse hídrico, são utilizadas em larga escala no estabelecimento de florestas industriais em vários países, entre os quais, destaca-se o Brasil com mais de 3 milhões de hectares plantados. O clima tropical e subtropical na maioria do território brasileiro permite um crescimento ininterrupto e, consequentemente, um rápido acúmulo de biomassa. Sabe-se que o crescimento e o desenvolvimento dos vegetais é conseqüência de vários processos fisiológicos, os quais são controlados pelas condições ambientais e características genéticas de cada espécie vegetal. Portanto, para melhor compreender o crescimento, o desenvolvimento e o impacto hidrológico de uma plantação de eucalipto, faz-se necessário conhecer os fatores que controlam o uso da água. Vários fatores ambientais influenciam a abertura e o fechamento estomático, determinando maior ou menor transferência de vapor de água para a atmosfera. Dentre estes, destacam-se os níveis de umidade do solo, o teor de umidade do ar, radiação solar, temperatura do ar e déficit de pressão de vapor. Especificamente, plantios com idade inicial de desenvolvimento apresentam descontinuidade na cobertura do solo, ficando estas plantas isoladas sujeitas a maior interação com a atmosfera, tendendo a apresentar maior exposição do dossel ao vento e a radiação solar, por isso, o tratamento aerodinâmico dado a esses plantios deve ser diferente em relação a plantios em idade adulta, com cobertura total do solo. Normalmente, os modelos de crescimento consideram na estimativa da condutância de superfície do vapor de água o dossel como uma folha grande, única e contínua (teoria da Big Leaf ). Esta aproximação não é adequada na etapa inicial de desenvolvimento de florestas. Esta idade em relação às outras tem uma grande importância, uma vez que nesse período as plantas apresentam maior taxa de crescimento, uma vez que o ganho de biomassa está diretamente relacionado aos processos de evapotranspiração (perda de vapor d água) e fotossíntese (ganho de CO2). Neste contexto, o objetivo deste estudo foi modelar a evapotranspiração para plantios de eucalipto em fase inicial de desenvolvimento. O sítio experimental está localizado numa área pertencente à Aracruz Celulose no município de Aracruz ES. Os dados meteorológicos, radiação solar, temperatura do ar, umidade relativa, velocidade do vento e precipitação foram coletados em uma torre de 38 m de altura localizada entre quatro árvores. A metodologia utilizada na modelagem da evapotranspiração baseou-se no trabalho de Angelocci (1996), quando o mesmo em seu estudo fez estimativas para a evapotranspiração de macieiras em pomares. Para a comparação dos resultados, estimou-se a evapotranspiração pelo método da Razão de Bowen por ser este um método que descreve bem a relação solo-planta-atmosfera. Após a análise dos resultados para todo o período estudado, verificou-se que para os estádios iniciais de desenvolvimento do eucalipto, o modelo desenvolvido se mostrou eficiente na estimativa da evapotranspiração.

VASCONCELOS, Manejo da cultura do girassol submetida a diferentes níveis de irrigação, doses e formas de aplicação de nitrogênio e potássio. 2012. 88 f. : Tese (doutorado) - Universidade Federal do Ceará, Centro de Ciências Agrárias, Departamento de Engenharia Agrícola, Programa de Pós-Graduação em Engenharia Agrícola, Fortaleza-CE, 2011. / Submitted by demia Maia (demiamlm@gmail.com) on 2016-08-04T14:34:08Z No. of bitstreams: 1 2011_tese_dvvasconelos.pdf: 1389440 bytes, checksum: 67fa2c33eae90b384f38d28417f28025 (MD5) / Approved for entry into archive by Nádja Goes (nmoraissoares@gmail.com) on 2016-08-04T14:40:48Z (GMT) No. of bitstreams: 1 2011_tese_dvvasconelos.pdf: 1389440 bytes, checksum: 67fa2c33eae90b384f38d28417f28025 (MD5) / Made available in DSpace on 2016-08-04T14:40:48Z (GMT). No. of bitstreams: 1 2011_tese_dvvasconelos.pdf: 1389440 bytes, checksum: 67fa2c33eae90b384f38d28417f28025 (MD5) Previous issue date: 2011 / The study aimed to evaluate the effects of three doses of nitrogen and potassium applied by the conventional method and by fertigation and witness - without application of N or K. We also evaluated the effects of six irrigation levels based on the Penman-Monteith ETo (EToPM), so that we can define an appropriate management for sunflower crop, variety Catissol 01. The experiment was conducted in the experimental area of the Meteorological Station of the Federal University of Ceará, located at the Campus do Pici, in the city of Fortaleza, from March to July 2008 for the experiments of nitrogen and potassium fertilization, and from August to December 2007 for the irrigation blades’ experiment. The experimental design was of randomized blocks with seven treatments and four replications for nitrogen and potassium fertilization and six treatments and four replications for irrigation blades. The doses tested in the nitrogen experiment were 0, 30, 60 and 120 kg ha-1 by conventional and fertigation method. In fertigation the nitrogen dosages were split into eight applications, the first of which was at sowing and the remaining were applied weekly. In conventional fertilization the dosages were split in two applications, being one third of the dose at planting and the other 2/3 at 30 days after germination. In the experiment with potassium the tested doses were 0, 25, 50 and 100 kg ha-1 and fertilized by conventional and fertigation methods. In fertigation dosages of potassium were split with 1/3 at planting and the remaining 2/3 split in five times during the crop cycle. In the conventional method potash fertilizer was all applied at planting. In the experiment of irrigation blades were tested blades with 25, 50, 75, 100, 125 and 150% EToPM. We analyzed the following variables in the experiments of nitrogen and potassium fertilization: yield, capitulum diameter and weight as well as 100 seed weight. In the experiment of irrigation blades, the following were analyzed: productivity, inflorescence capitulum diameter and weight. The application of nitrogen by conventional method and fertigation showed significant responses to capitulum diameter and weight. The highest yield (3429 kg ha-1) was obtained with conventional fertilization, with a great dose estimated at 80,97 kg ha-1 of N. Potassium fertilizer applied by conventional method and fertigated showed significant responses for all analyzed variables, being the highest yield (3.312,09 kg ha-1) achieved by the conventional method, with a dose estimated at 61,24 kg ha-1 of K2O. In the irrigation blades experiment, significant differences were obtained for the following variables: productivity and weight of the chapter, obtaining a maximum yield of 3.357,18 kg ha-1 with an irrigation blade estimated in 91,06 % EToPM / O trabalho teve como objetivo avaliar os efeitos de três doses de nitrogênio e de potássio aplicadas pelo método convencional e por fertirrigação e testemunha – sem aplicação de N ou K. Também, foi avaliado os efeitos de seis lâminas de irrigação com base na ETo de Penman-Monteith (EToPM), para que se possa definir um manejo adequado para a cultura do girassol, variedade Catissol 01. O experimento foi conduzido na área experimental da Estação Meteorológica da Universidade Federal do Ceará, localizada no Campus do Pici, no município de Fortaleza, no período de março a julho de 2008 para os experimentos de adubação nitrogenada e potássica, e de agosto a dezembro de 2007 para o experimento de lâminas de irrigação. O delineamento experimental foi de blocos ao acaso com sete tratamentos e quatro repetições para adubação nitrogenada e potássica e de seis tratamentos e quatro repetições para lâminas de irrigação. As doses testadas no experimento de nitrogênio foram: 0; 30; 60 e 120 kg ha-1 pelo método convencional e fertirrigado. Na fertirrigação as dosagens de nitrogênio foram parceladas em oito aplicações, sendo a primeira na semeadura e as demais aplicadas semanalmente, na adubação convencional as dosagens foram parceladas em duas aplicações, sendo 1/3 da dose no plantio e os outros 2/3 aos 30 dias após a germinação. No experimento com potássio as doses testadas foram: 0; 25; 50 e 100 kg ha-1 pelo método convencional e fertirrigado. Na fertirrigação as dosagens de potássio foram parceladas com 1/3 no plantio e os outros 2/3 parcelados em cinco vezes durante o ciclo da cultura, na adubação convencional o potássio foi todo aplicado no plantio. No experimento de lâminas de irrigação foram testadas as lâminas com 25; 50; 75; 100; 125 e 150% EToPM. Foram analisadas as seguintes variáveis nos experimentos de adubação nitrogenada e potássica: produtividade, diâmetro do capítulo, peso do capítulo e peso de 100 sementes. No experimento de lâminas de irrigação foram analisadas: a produtividade, o diâmetro do capítulo e o peso do capítulo. A aplicação de nitrogênio pelo método convencional e por fertirrigação apresentaram respostas significativas para: produtividade, diâmetro do capítulo e peso do capítulo. A máxima produtividade (3.429 kg ha-1) foi obtida com adubação convencional, com uma dose ótima estimada em 80,97 kg ha-1 de N. A adubação potássica, aplicada pelo método convencional e fertirrigada, apresentou respostas significativas para todas as variáveis analisadas, sendo a maior produtividade (3.312,09 kg ha-1) conseguida pelo método convencional, com uma dose estimada em 61,24 kg ha-1 de K2O. No experimento de lâminas de irrigação, foram obtidas diferenças significativas para as variáveis: produtividade e peso do capítulo, obtendo-se uma produtividade máxima de 3.357,18 kg ha-1 com uma lâmina de irrigação estimada em 91,06 % EToPM.