Thesis (M.S.)--Oregon State University, 1997. / Typescript (photocopy). Includes bibliographical references (leaves 71-73). Also available via the World Wide Web.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1974. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.Eng.Sc.)--University of Adelaide, Dept. of Civil and Environmental Engineering, 1995. / Undertaken in conjunction with JUMP (Joint Universities Masters Programme in Hydrology and Water Resources). Bibliography: leaves 76-83.

Water conservation practices are being widely implemented to alleviate sediment and nutrient losses from agricultural land and unsustainable groundwater use for irrigation. Tailwater recovery (TWR) systems are conservation practices being implemented to collect and store runoff to reduce nutrient losses and provide a source of irrigation water. This collection of research is focused on evaluating TWR systems through the following actions: 1) investigate ability to reduce solids and nutrients delivery to downstream systems, 2) compare differences in solid and nutrient concentrations in surface water samples from TWR systems to irrigation water from a TWR systems; 3) determine the potential to irrigate water containing solids and nutrients; 4) quantify a water budget for TWR systems; 5) conduct cost and benefit analyses of TWR systems; and 6) analyze economic cost to reduce solids and nutrients and to retain water. Tailwater recovery systems did not significantly reduce concentrations of solids and nutrients; however, loads of solids, P, and N were significantly reduced by 43%, 32% and 44%, respectively. Mean nutrient loads per hectare available to be recycled onto the landscape were 0.20 kg ha-1 P and 0.86 kg ha-1 N. Water budget analyses show these systems save water for irrigation but were inefficient. Net present value (NPV) and benefit cost ratios were positive and >1 for producers who owned the land, but remained <1 if land was rented. However, beyond improvements to irrigation infrastructure, farms with a TWR system installed lost NPV of $51 to $328 per ha. Mean total cost to reduce solids using TWR systems ranged from $0 to $0.77 per kg, P was $0.61 to $3,315.72 per kg, and N was $0.13 to $396.44 per kg. The mean total cost to save water using TWR systems ranged from $189.73 to $628.23 per ML, compared to a mean cost of groundwater of $13.99 to $36.17 per ML. Mechanistically, TWR systems retain runoff on the agricultural landscape, thereby reducing the amount of sediment and nutrients entering downstream waterbodies and provide an additional source of water for irrigation; however, more cost-effective practices exist for nutrient reduction and providing water for irrigation.

Thesis (PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Soilless production of crops relies on the addition of high concentrations of nutrients with the irrigation water. The drained nutrient solution should be re-used to reduce the risk of pollution and to increase the water- and nutrient use efficiency of the system. Besides the risk of pathogen build-up, one of the main impediments of a wider application of this method is the frequent analysis required to maintain optimum nutrient concentrations and ratios in the rootzone. Yield reductions may be caused by an unbalanced nutrient solution. Alternatively the addition level of nutrients can be calculated through the use of nutrient uptake models that simulate the change in the re-circulated nutrient solution. To simulate crop water and nutrient demand necessary for model based regulation it was necessary to quantify the key factors affecting nutrient uptake by plants. The nutrient solution concentration and ratios between the macro-nutrients affected the uptake of water and nutrients. The total nutrient uptake per root dry weight increased and more specifically the nitrate (NO3 -), phosphate (H2PO4 -), potassium (K+) and sulphate (SO4 2-) uptake increased with an increase in nutrient solution electrical conductivity (EC) from 0.8 to 4.0 mS cm-1 while water uptake decreased. Except for Ca2+ uptake there was no correlation between nutrient and water uptake. Nutrient uptake can thus not be calculated based on water uptake. Instead a mechanistic high-affinity Michaelis-Menten based model can be used to estimate macro-nutrient uptake (Un, mg m-2 hr-1). Water and nutrient uptake was also affected by the solar radiation levels. Since nutrient uptake is related to the growth rate, solar radiation levels can be expected to influence nutrient uptake. The uptake of all ions increased with an increase in the solar radiation levels and for NO3 -, K+ and H2PO4 - the uptake rate was higher at higher nutrient solution concentrations. The Michaelis-Menten based model was adjusted to incorporate the effect of solar radiation levels on nutrient uptake. Water uptake (Wu, L m-2 day-1) was simulated as a function of crop transpiration and crop leaf area using a linear regression model, but since leaf area development was affected by solar radiation levels this was additionally incorporated into the estimation of the leaf area index (LAI). The composition of the nutrient solution also affected the biomass allocation of the crop which can again affect nutrient use as well as the fruit yield. There was also a direct effect of nutrient solution composition on fruit yield and quality with higher EC’s resulting in smaller fruit but an increase in fruit dry matter %, total soluble solids (TSS), titratable acidity (TA) and lycopene content. The results in this thesis make a valuable contribution to our understanding of the effect of nutrient availability (concentration and ratios) and nutrient requirement for growth (solar radiation levels) on nutrient uptake. Incorporating these into nutrient uptake models resulted in the development of a handy tool to simulate changes in composition of re-circulating nutrient solutions ultimately resulting in an improvement of the water and nutrient use efficiency of soilless systems. / AFRIKAANSE OPSOMMING: Die grondlose verbouing van gewasse is afhanklik van toediening van voedingselemente teen hoë peile in die besproeiingswater. Die voedingsoplossing wat dreineer moet hergebruik word om die risiko van besoedeling te verminder en ook om die water en nutriënt verbruik doeltreffendheid van die sisteem te verbeter. ʼn Ongebalanseerde voedingsoplossing kan ʼn verlaging in opbrengste veroorsaak. Benewens die risiko van patogene wat opbou, is die gereelde analises nodig word vir die handhawing van optimale nutriënt konsentrasies en verhouding tussen elemente in die wortelsone een van die hoof faktore wat ʼn meer algemene gebruik van die metode verhoed. Alternatiewelik kan die nutriënt toedieningspeile bereken word deur voedingstof opname modelle en simulasie van die verandering in water en nutriente wat dreineer. Om ʼn model gebaseerde reguleringsmetode daar te stel was dit nodig om die belangrikste faktore wat nutriënt opname beïnvloed te kwantifiseer. Beide die konsentrasie van die voedingsoplossing en die verhouding tussen elemente het ‘n effek gehad op die opname van water en nutriënte. Die totale nutriënt opname per wortel droë massa het toegeneem. Terwyl water opname afgeneem het met ‘n toename in die elektriese geleding (EG) van die voedingsoplossing vanaf 0.8 tot 4.0 mS cm-1 het die nitraat (NO3 -), fosfaat (H2PO4 -), kalium (K+) en sulfaat (SO4 2-) opname verhoog. Behalwe vir Ca2+ opname was daar geen korrelasie tussen water en nutriënt opname nie. Nutriënt opname kan dus nie bepaal word gebaseer op wateropname nie. Alternatiewelik is die gebruik van ʼn meganistiese hoë-affiniteit Michaelis-Menten-gebaseerde model voorgestel om die opname van makro-nutriente (Un, mg m-2 hr-1) te bepaal. Water- en voedingstofopname is beinvloed deur die ligintensiteit vlakke. Voedingsopname word bepaal deur die groei van die plant, daarom is dit verwag dat ligintensiteit vlakke die opname van voedingstowwe sal beïnvloed. Die opname van al die ione het toegeneem met 'n toename in die ligintensiteit vlakke en die tempo van NO3 -, K+ en H2PO4 - opname was hoër by 'n hoër voedingsoplossing konsentrasie. Die Michaelis-Menten gebaseerde model is aangepas om die effek van ligintensiteit vlakke op nutriënt opname te inkorporeer. Opname van water (Wu, L m-2 dag-1) is gesimuleer as 'n funksie van transpirasie en blaaroppervlakte met behulp van 'n lineêre regressiemodel en aangesien die blaaroppervlak ontwikkeling ook deur ligintensiteit vlakke beïnvloed word, is dit opgeneem in die skatting van die blaaroppervlakte-indeks (LAI). Die samestelling van die voedingsoplossing het die biomassa verspreiding beïnvloed. Dit kan nutriënt gebruik en vrug opbrengs beïnvloed. Die voedingsoplossing samestelling het vrug opbrengs en - kwaliteit beinvloed met kleiner vrugte, maar 'n toename in droëmateriaal %, totale oplosbare vastestowwe (TOVS), titreerbare suur (TA) en likopeen inhoud by ʼn hoër EG. Die resultate in hierdie tesis lewer 'n waardevolle bydrae tot ons begrip van die effek van nutriënt beskikbaarheid (konsentrasie en verhoudings) en voedingstof behoefte vir groei (ligintensiteit vlakke) op voedingsopname. Deur die inligting te inkorporeer in voedingsopname modelle het gelei tot die ontwikkeling van 'n handige instrument om die veranderinge in die samestelling van hersirkulerende voedingsoplossings te simuleer. Dit lei gevolglik tot die verbetering van die water en voedingstof gebruik doeltreffendheid van grondlose stelsels.

Thesis (Ph. D.)--University of Washington, 1994. / Vita. Includes bibliographical references (leaves [134]-156).

Orientador: Roberto Testezlaf / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola / Made available in DSpace on 2018-08-25T15:27:01Z (GMT). No. of bitstreams: 1 Deus_FabioPoncianode_D.pdf: 3789780 bytes, checksum: 28bcab8caeed4c093a51c402f46be203 (MD5) Previous issue date: 2014 / Resumo: A dificuldade em definir parâmetros operacionais nos processos de filtração e retrolavagem em filtros de areia utilizados na irrigação localizada é causada pela complexidade de fixar adequadamente os valores da taxa de filtração e da vazão de retrolavagem a partir das características físicas da areia e dos componentes internos do equipamento. Neste contexto, o presente trabalho visou contribuir com informações técnico-científicas sobre o comportamento da eficiência de remoção nos processos de filtração e retrolavagem de um modelo comercial de filtro de areia para diferentes condições de operação e características físicas da areia, para um determinado nível de contaminação da água. Os ensaios experimentais, realizados em três filtros de areia de um mesmo modelo comercial, basearam-se na utilização combinada de três granulometrias de areia (fina, média e grossa) e quatro taxas de filtração (20, 40, 60 e 75 m3 m-2 h-1), em três ciclos de filtração (C1, C2 e C3). Os ensaios de filtração tiveram duração fixa de quatro horas, sendo os ensaios de retrolavagem realizados nos leitos contaminados pela filtração, com duração fixa de quinze minutos depois de atingida uma expansão de 25% do leito filtrante. Os parâmetros de perda de pressão e eficiência de remoção em ambos os processos foram avaliados ao longo do tempo de ensaio. De maneira geral, a filtração foi efetiva na remoção de partículas em suspensão na água a partir do tamanho correspondente à areia fina, com a retenção ocorrendo predominantemente na camada superficial do leito filtrante. O valor da eficiência de remoção na filtração aumentou com o incremento da taxa de filtração, com a diminuição da granulometria de areia, e reduzindo a sua efetividade com o tempo de filtração. Na retrolavagem, as velocidades superficiais utilizadas para a manutenção dos 25% de expansão do leito filtrante determinaram os maiores índices de sólidos removidos e de eficiência de limpeza nas camadas dos leitos filtrantes com maior nível de contaminação, com diminuição dos seus valores nos ciclos de filtração posteriores. A metodologia de avaliação da filtração utilizando informações de sólidos retidos na areia se mostrou com maior potencial de representatividade quando comparado à metodologia convencional de coleta pontual de amostras de água / Abstract: The difficulty in defining operating parameters in filtration and backwash processes of the sand filter used in localized irrigation is caused by the complexity to set suitably filtration rate and backwash flow from physical characteristics of the sand and of internal components of the equipment. In this context, this work aims to contribute with technical-scientific information about the behavior of the filtration and backwash processes removal efficiency in a commercial model of sand filter for different operation conditions and sand physical characteristics, for a defined water contamination level. Experimental trails, performed in three sand filter of the same commercial model, were based in the combined use of three sand particle sizes (fine, medium and coarse) and four filtration rates (20, 40, 60 e 75 m3 m-2 h-1), in three filtration cycles (C1, C2 e C3). The filtration tests had fixed period of four hours and the backwash trails were performed in the unclean beds produced by filtration, with 15 minutes duration, after reached an filtration bed expansion of 25%. The parameters of pressure loss and removal efficiency in both processes were evaluated over the experimental time. Usually, the filtration was effective to remove suspended water particles up to the size corresponding to fine sand, with predominant action on the surface filter layer The value of filtration removal efficiency increased with increasing values of the filtration rate, with decreasing of sand particle size and reducing its effectiveness with filtration time. In the backwash process, the superficial velocities used to maintain the filtration layer expansion of the 25% determined highest rates of removed solids and cleaning efficiencies in layers with higher contamination levels, with decreasing values along the cycles. The filtration assessment methodology using values of solids retained in the sand showed the greatest potential of the representativeness in the evaluation process when compared to conventional methods of point water samples collected over time / Doutorado / Agua e Solo / Doutor em Engenharia Agrícola

Please read the abstract in the section 00front of this document / Dissertation (MSc (Soil Science))--University of Pretoria, 2005. / Plant Production and Soil Science / unrestricted

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The implantation system with rised beds and the use of surface irrigation can be important practices to increase efficiency of the drainage process and ensure the proper establishment of culture in the system of rotation, as well as ensuring the expression of the productive potential of maize in irrigated rice areas. In this way, the objectives of this study were: to assess the response of maize grown in irrigated rice areas as agronomic characteristics, yield components and grain yield under different deployment systems and surface irrigation; and evaluate the efficiency of water use by the culture of maize for the irrigated area treatments in different implantation systems. To reach the objectives, two field experiments were conducted during the crop 2014/15 in experimental systematized area of irrigated rice at the Universidade Federal de Santa Maria-RS. The experiment I, consisted of a factorial, conducted in random blocks design with four replications. The factor levels were composed by deployment systems: A1 = with rised beds; A2 = without rised beds; and factor D levels consisting of: D1 = with irrigation; D2 = without irrigation. Already the experiment II was conducted in random blocks design with two treatments: T1 = Irrigation by furrows; T2 = Witness (without irrigation), both in rised beds, with four replicates. Hybrid maize seeds were used AG9045 in both experiments. The results obtained show that use of the implantation system with rised beds provides an increase in agronomic characteristics of growth and maize yield components as well as increased efficiency of water use and increase in grain yield compared to the system without rised beds. The use of irrigation in periods of drought increases the maize yield in irrigated rice areas, regardless of the implantation system used. The combination of the implantation system with rised beds and furrow irrigation provides greater increase in maize yield, compared to the tested systems. / O sistema de implantação com camalhão e a utilização da irrigação por superfície podem ser práticas importantes para aumentar a eficiência do processo de drenagem e garantir o estabelecimento adequado da cultura no sistema de rotação, além de assegurar a expressão do potencial produtivo do milho em áreas de arroz irrigado. Nesse sentido, os objetivos do presente trabalho foram: avaliar a resposta do milho cultivado em áreas de arroz irrigado quanto às características agronômicas, componentes de rendimento e rendimento de grãos, sob diferentes sistemas de implantação e irrigação por superfície; e avaliar a eficiência de uso da água pela cultura do milho para os tratamentos irrigados por superfície nos diferentes sistemas de implantação. Para o atendimento dos objetivos, dois experimentos de campo foram conduzidos durante a safra 2014/15 em área experimental sistematizada de arroz irrigado da Universidade Federal de Santa Maria - RS. O experimento I, constituiu-se de um fatorial, conduzido em delineamento de blocos ao acaso com quatro repetições. Os níveis para o fator A foram compostos pelos sistemas de implantação: A1= com camalhão; A2= sem camalhão; e os níveis do fator D compostos por: D1= com irrigação; D2= sem irrigação. Já o experimento II foi conduzido em delineamento de blocos ao acaso com dois tratamentos: T1 = Irrigação por sulcos; T2 = Testemunha (sem irrigação), ambos sobre camalhões, com quatro repetições. Foram utilizadas sementes do milho híbrido AG9045 em ambos os experimentos. Os resultados obtidos evidenciam que a utilização do sistema de implantação com camalhão proporciona aumento em características agronômicas de crescimento e em componentes de rendimento do milho, além de maior eficiência do uso da água e acréscimo no rendimento de grãos, comparativamente ao sistema sem camalhão. O uso da irrigação em períodos de déficit hídrico no solo aumenta o rendimento de grãos de milho cultivado em áreas de arroz irrigado, independente do sistema de implantação utilizado. A combinação entre o sistema de implantação com camalhão e a irrigação é a que proporciona maior acréscimo no rendimento de grãos de milho, em relação aos sistemas testados.

Made available in DSpace on 2015-03-26T13:39:56Z (GMT). No. of bitstreams: 1 texto completo.pdf: 239817 bytes, checksum: 1921cc10636b0f1980cf9299b9b45fac (MD5) Previous issue date: 2011-02-15 / The high dilutions applied according to the principles of homeopathy or hormesis are sustainable alternatives in agriculture low cost and can be used to improve water quality. Four experiments were conducted at the Laboratory of Homeopathy, Plant Science Department, Universidade Federal de Viçosa. The objective was to investigate the change of physicochemical properties of water in response to action of high dilutions of Alumina and Calcarea carbonica in a completely randomized design with seven treatments (3CH, 5CH, 7CH, 9CH, 11CH, 13CH and distilled water, as control) and four replications. The dynamizations were prepared in distilled water, and were applied in the procedure "double blind". Fifty-six bottles of borosilicate glass with a capacity of 80 mL received 40 mL of distilled water, and twenty-eight in the first experiment and twenty-eight in the second. Fifty-six bottles of borosilicate glass with a capacity of 80 mL received 40 mL of acidic water. In twenty-eight of these were applied 10 drops of Alumina in the remaining twenty-eight were applied 10 drops of Calcarea carbonica. The variables were: potential of hydrogen, electrical conductivity (in &#956;S/cm) and dissolved oxygen (mg/L), measured immediately after treatment (T1) and every 24 hours until 72 hours after (T2, T3, T4). The data were interpreted by analysis of variance, using the program SAEG. The control was compared with other treatments by Dunnett test at 5% probability. Alumina 3 CH in distilled water increased the potential of hydrogen and electrical conductivity and Alumina 7 CH reduced the dissolved oxygen. The Calcarea carbonica 5 CH and 7 CH increased the potential of hydrogen from distilled water. The 7 CH increased dissolved oxygen, the 9 CH and 13 CH reduced it. In the treatment of water acidity caused by aluminum the calcarea carbonica showed efficiency and Alumina not been efficient. / As altas diluições aplicadas conforme os princípios da homeopatia ou da hormese são alternativas sustentáveis de baixo custo na agricultura, podendo ser usadas para melhorar a qualidade das águas. Foram conduzidos quatro experimentos no Laboratório de Homeopatia do Departamento de Fitotecnia da Universidade Federal de Viçosa. Objetivou-se investigar a alteração das propriedades físico-químicas de água em resposta à ação de altas diluições de Alumina e Calcarea carbonica no delineamento inteiramente casualizado com sete tratamentos (3 CH, 5 CH, 7 CH, 9 CH, 11 CH e 13CH e água destilada, como testemunha) e quatro repetições. As dinamizações foram preparadas em água destilada e aplicadas no procedimento duplo-cego . Cinquenta e seis frascos de vidro borossilicato com capacidade para 80 mL receberam 40 mL de água destilada, sendo 28 no primeiro experimento e 28 no segundo. Cinquenta e seis frascos de vidro borossilicato com capacidade para 80 mL receberam 40 mL de água ácida. Em 28 desses, foram aplicadas 10 gotas da Alumina, enquanto nos 28 restantes, 10 gotas da Calcarea carbonica. As variáveis avaliadas foram: potencial de hidrogênio, condutividade elétrica (em &#956;S/cm) e oxigênio dissolvido (em mg/L), medidas imediatamente após a aplicação dos tratamentos (T1) e em intervalos de 24 horas até 72 horas após (T2, T3, T4). Os dados foram interpretados por meio de análise de variância, sendo utilizado o Programa SAEG. A testemunha foi comparada com os demais tratamentos pelo teste de Dunnett a 5% de probabilidade. A Alumina 3 CH na água destilada elevou o potencial de hidrogênio e a condutividade elétrica, a Alumina 7 CH reduziu o oxigênio dissolvido, a Calcarea carbonica 5 CH e a 7 CH elevaram o potencial de hidrogênio da água destilada, a 7 CH aumentou o oxigênio dissolvido e a 9 CH e 13 CH reduziram-no. No tratamento da acidez da água causada por alumínio, a Calcarea carbonica foi eficiente e a Alumina não.