Diss. (sammanfattning) Stockholm : Karolinska institutet, 2010.

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Un problème majeur de l’industrie vinicole est la difficulté à contrôler la cristallisation des sels tartriques. Ce phénomène confère une image négative chez les consommateurs, en particulier pour les vins effervescents dont l’instabilité tartrique provoque le débordement (ou gerbage) de la bouteille. La cristallisation de ces sels ioniques modifie l’équilibre acido-basique des vins qui influence leurs qualités organoleptiques. Parmi les méthodes de contrôle préventif, l’utilisation de carboxyméthylcellulose (CMC) a été autorisée dans les vins depuis 2009. Les CMC sont des polyélectrolytes que l’on retrouve sous forme de sels de sodium. Cette famille de macromolécules a démontré son pouvoir inhibiteur de la cristallisation des sels tartriques, mais le mécanisme précis reste encore incompris, ce qui empêche de fait l’optimisation des propriétés de ces CMC à travers les processus de fabrication développés par la société CELODEV. Les travaux de cette thèse visent à expliciter les mécanismes en jeu. La première partie est consacrée à la discrimination des propriétés des CMC pour améliorer l'effet inhibiteur des sels tartriques dans les solutions hydroalcooliques. La caractérisation des CMC concerne un large éventail de propriétés physico-chimiques de la CMC notamment le degré de substitution (DS) déterminé par RMN, la répartition des substituts le long de la chaine du polymère par méthode RMN et HPLC, le degré de polymérisation (DP) déterminé par viscosimétrie intrinsèque, le poids moléculaire déterminé par SEC-MALLS, le taux de cristallinité (Ic) et la stabilité du polymère déterminée par analyse thermique. D’autre part, les propriétés de charges du polyélectrolyte dans son milieu solvant ont été étudiées. Une méthode a été développée dans le cadre de ces travaux pour évaluer la densité de charges des CMC afin de comprendre le comportement qu’elles peuvent avoir en fonction de leurs propriétés physico-chimiques et des conditions du milieu. La deuxième partie de l’étude distingue les effets thermodynamiques et cinétiques de l’ajout de CMC dans des solutions modèles hydro-alcooliques – sels – CMC. La présence d'additifs dans une solution sursaturée peut influencer tous les paramètres de la cristallisation notamment la solubilité et la nucléation/croissance des cristaux. Dans cette étude, les solubilités des sels tartriques ont été déterminées expérimentalement, puis modélisée par un modèle thermodynamique permettant de prendre en compte la complexité du système composé de sels, alcool, et macromolécule. Les additifs dans ces travaux ne modifient pas la solubilité. Dans un second temps l’étude cinétique de cristallisation de ces sels en milieu hydro-alcoolique est réalisée avec la détermination de fréquences de nucléation des sels en milieu sursaturé (en présence ou non d’additifs) à travers des mesures de temps d’induction. Ces études de nucléation confirment l’inhibition importante des sels tartriques en présence des CMC et donne des informations concrètes sur le mécanisme de formation des cristaux en solution. Enfin, une analyse morphologique des cristaux a permis de montrer comment ces additifs modifient le faciès cristallin notamment sur la face {010}. La troisième et dernière partie utilise les deux précédentes parties pour définir les mécanismes hypothétiques sur l’inhibition tartrique par les CMC. En recoupant l’ensemble des propriétés des CMC, il a été démontré que les plus efficaces avaient un DS compris entre 0,90 et 0,95, un Ic faible pour avoir une flexibilité suffisante, un DP faible pour assurer une certaine accessibilité des charges pouvant s’adsorber sur les cristaux de KHT. Les approches phénoménologiques développées dans cette thèse ont permis de lever les verrous scientifiques concernant les modes d’actions des additifs de cristallisation sur les sels tartriques en vue de mettre en place des critères permettant le choix des CMC les plus performantes parmi toute la gamme pour le milieu vinicole. / A major problem in the wine industry is the difficulty to control tartaric salts crystallization, which causes a negative feeling among consumers particularly in sparkling wine which causes excessive gushing. The crystallization of these ionic salts also changes the acid-base balance of the wine, which influences the organoleptic qualities of wines. Amongst the methods of control, the use of cellulose gums or carboxymethyl cellulose (CMC) was authorized for wine production since 2009. These CMCs are macromolecular polyelectrolytes in the form of sodium salts. This family of macromolecules has demonstrated its inhibitory power, but the precise mechanism is not fully understood yet. This currently prevents the optimization of the manufacturing process of these gums by the CELODEV Company. The aim work of this thesis is based on three main parts. The first part is devoted to the discrimination of the properties of carboxymethylcelluloses to improve the inhibitory effect face to tartaric salts in hydro alcoholic solutions. A whole study on the characterization of CMCs has been made. First, It deals with the physicochemical properties of CMC, which are the degree of substitution (DS) determined by NMR, the distribution of substitutes along the polymer chain by NMR and HPLC method, the degree of polymerization (DP) determined by viscometry, the molecular weight determined by SEC-MALLS and GPC, the degree of crystallinity (Ic) and the stability of the polymer determined by thermal analysis. Secondly, the charge properties of this polyelectrolyte depending on the medium has been studied. A method has been developed as part of this work to evaluate the charge density (q) of CMCs in order to understand the behaviour that these can have according to their physico-chemical properties and environmental conditions. The second part of the study is devoted to the study of the thermodynamics of hydro-alcoholic solutions - salts - CMC. The presence of additives in a supersaturated solution can influence all the parameters of the crystallization, in particular the solubility and the nucleation / growth of the crystals. In this study, the solubilities of tartaric salts were determined experimentally by a classical approach, then modelled by a thermodynamic model allowing to take into account the complexity of the system composed of salts, alcohol, and macromolecule. The additives do not change the solubility. In a second part, the kinetic study of crystallization of these salts in a hydro-alcoholic medium was approached with the determination of the frequency of nucleation in a supersaturated salts medium (with or without additives), determined from a measurement of induction time. These nucleation studies have provided concrete information on the crystal formation mechanism in solution. Finally, a morphological analysis of the crystals made it possible to show how these additives modify the crystalline facies especially on the {010} face. The third and last part defines the hypothetical mechanisms that CMCs have on tartaric inhibition. By cross-checking all the properties of the CMCs, it has been shown that the most effective CMCs have a DS between 0.90 and 0.95, a weak Ic to have sufficient flexibility and a low DP to ensure a certain accessibility of the crystal lattice for adsorption on THK crystals. Phenomenological approaches developed in this thesis will remove the barriers on the knowledge of the action mechanisms of additives on the crystallization of tartaric salts. Results will also help establish criteria for the selection of the most efficient CMC across the range for the wine-making industry.

La valorisation chimique des espèces condensables issues de la torréfaction de biomasse ainsi que l'utilisation d'un gaz vecteur à faible coût, tels que les gaz de combustion, peuvent constituer des étapes importantes pour le développement du procédé de torréfaction à l'échelle industrielle. Les rendements des espèces condensables varient selon la composition de la biomasse, notamment par la présence de certains minéraux, et varient aussi en fonction de conditions opératoires telles que le gaz vecteur utilisé. Afin d'étudier l'effet du potassium sur la perte de masse de la biomasse et sur le rendement des espèces condensables, trois biomasses déminéralisées ont été imprégnées avec différentes concentrations de K2CO3 puis torréfiées à 275°C jusqu'à l'obtention d'une perte de masse cible (25 ou 30%). La torréfaction a été effectuée à la fois dans un instrument d'analyse thermogravimétrique (ATG) et dans un réacteur à l'échelle laboratoire sous azote et en présence de gaz de combustion. Des analyses ATG des biopolymères (cellulose, xylane et lignine) bruts et imprégnés avec du K ont été réalisées pour faciliter l'interprétation des résultats. La perte de masse augmente lorsque la teneur en K des biomasses augmente et, par conséquent, des temps de séjour plus courts sont suffisants pour obtenir la perte de masse cible. Cela semble être principalement le résultat du décalage de la décomposition de la cellulose vers des températures plus faibles. Les vitesses de réaction maximales sont bien plus élevées en présence de gaz de combustion car la biomasse subit des réactions d'oxydation en plus de la décomposition classique. Quelle que soit l'atmosphère, K inhibe la production d’anhydrosaccharides (levoglucosan, LAC et DGP) et de furanes (à l'exception du 2-furanmethanol). En parallèle, une augmentation substantielle du rendement en acétol est constatée. La rupture du cycle pyranose de la cellulose qui entraine la formation des produits légers est favorisée en présence de K au détriment de la dépolymérisation qui produit du levoglucosan. Le K favorise la production de 2-furanmethanol, syringol et guaiacol surtout en présence de gaz de combustion. En revanche, la production de vanilline et de syringaldéhyde est défavorisée en présence de K tandis qu'elle est fortement favorisée en présence de gaz de combustion quand la biomasse est libre de K. L'effet du K sur les rendements des espèces condensables lors de la torréfaction de la biomasse est démontré quelle que soit la nature de l'atmosphère. De plus, dans les conditions testées, l'oxygène présent dans l'atmosphère intensifie, dans une mesure plus ou moins grande, la tendance imposée par le K / The chemical valorization of condensable species from biomass torrefaction as well as the use of a low-cost carrier gas such as flue gas may be important steps for industrial-scale implementation of torrefaction. The condensable species yield varies according to the biomass composition, in particular by the presence of certain minerals, and also changes according to the operating conditions such as the gas atmosphere. In this context, to investigate the effect of potassium on mass loss of biomass during torrefaction and in the yield of condensable species, three demineralized biomasses were impregnated with different concentrations of K2CO3 and then torrefied at 275°C up to a target mass loss (25 or 30%). Torrefaction was carried out in both a thermogravimetric analysis (TGA) instrument and a laboratory fixed-bed reactor under nitrogen and flue gas atmospheres. TGA of raw and K-impregnated biopolymers (cellulose, xylan and lignin) were performed to facilitate interpretation of the results. When K content increased in the biomass, shorter torrefaction times were sufficient to obtain the targeted mass loss. This behavior seems to be a result of shifting the cellulose decomposition to lower temperatures. The maximum reaction rates are much higher under flue gas because the biomass undergoes oxidation reactions in addition to the ordinary decomposition. Regardless of the gas atmosphere employed, K inhibits the production of anhydrosugars (levoglucosan, LAC and DGP) and furans (except 2-furanmethanol). This suppression is accompanied by a substantial increase in acetol yield. The cleavage of pyranose rings in cellulose which results in the formation of low molecular weight compounds is favored in the presence of K to the detriment of the depolymerization which delivers levoglucosan. K promotes the production of 2- furanmethanol, syringol and guaiacol especially under flue gas atmosphere. However, the yields of vanillin and syringaldehyde decreased in the presence of K whereas they are strongly favored under flue gas atmosphere when the biomass does not contain K. The effect of K on the yields of condensable species from biomass torrefaction is demonstrated whatever the gas atmosphere. Moreover, under the conditions tested, the oxygen present in the atmosphere intensifies, to a greater or lesser extent, the tendency imposed by the K

La combustion de résidus de biomasse, généralement peu valorisés, pourrait apporter une solution d’approvisionnement intéressante pour la production d’énergie, allégeant la pression sur les ressources forestières. Toutefois, la composition chimique de ces résidus est à l’origine de problèmes techniques autant qu’environnementaux dans les procédés de combustion existants, ce qui limite leur utilisation. Deux de ces problèmes ont été traités dans cette thèse : les émissions de NOX et la quantité de potassium volatilisée lors de la combustion de différents résidus. Des essais de combustion ont été menés dans des réacteurs à l’échelle du laboratoire, sur des granulés de biomasse pure ou en mélange. Contrairement à la volatilisation du potassium, qui est liée à la teneur en différents éléments inorganiques, une relation linéaire forte (R² = 0,98) entre les émissions de NOX et la teneur en azote du combustible a été établie pour les granulés de biomasse pure. Des écarts par rapport à cette relation linéaire ont été observés dans le cas des essais menés sur des granulés de mélange, mettant en relief que la teneur en azote n’est pas le seul paramètre impliqué. Les travaux menés ont ainsi permis d’établir de manière originale que des synergies peuvent exister dans les granulés de mélange de résidus de biomasse, conduisant à des comportements différant de l’additivité directe des comportements des biomasses prises séparément. Ces synergies permettraient d’atténuer les problèmes causés par l’utilisation de ces résidus dans des chaudières en agissant de manière ingénieuse directement sur les propriétés des combustibles sans modification du procédé. / Combustion of biomass residues, which are generally poorly valued, could provide an attractive supply solution for energy production, alleviating pressure on forest resources. However, the chemical composition of these residues is causing both technical and environmental problems in existing combustion processes, which limits their use. Two of these problems have been addressed in this thesis: the amount of volatilized potassium and NOX emissions, when burning different residues. Combustion tests have been conducted in laboratory-scale reactors on pure and mixed biomass pellets. Variations in the amount of volatilized potassium was found to be linked to the content of multiple chemical elements for pure biomass pellets. In the case of NOx emissions, a strong correlation (R² = 0.98) with the nitrogen content of the fuel was found for pure biomass pellets. However, deviations from this linear relationship were observed for trials conducted on mixed biomass pellets, highlighting that the nitrogen content is not the only parameter involved. The work carried out thus made it possible to establish in an original way that synergies can exist in the pellets made of a mixture of biomass residues, leading to beneficial behaviors differing from the direct additivity of the biomass behaviors taken separately. These synergies could allow to mitigate the problems caused by the use of these residues in boilers by ingeniously acting directly on the properties of the fuels without modification of the process.

Submitted by Liliane Ferreira (ljuvencia30@gmail.com) on 2018-12-12T10:02:58Z No. of bitstreams: 2 Dissertação - Aline Franciel de Andrade - 2018.pdf: 1492416 bytes, checksum: 6293e6675f7f5fb02fd7a76c15ca9aa1 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-12-12T10:33:07Z (GMT) No. of bitstreams: 2 Dissertação - Aline Franciel de Andrade - 2018.pdf: 1492416 bytes, checksum: 6293e6675f7f5fb02fd7a76c15ca9aa1 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-12-12T10:33:07Z (GMT). No. of bitstreams: 2 Dissertação - Aline Franciel de Andrade - 2018.pdf: 1492416 bytes, checksum: 6293e6675f7f5fb02fd7a76c15ca9aa1 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-11-26 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / The sugarcane crop stands out as the most used renewable energy source in Brazil presenting high yields and good adaptation to Brazilian soil and climate conditions. Due to the high biomass production, the nutrient uptake from soil is also high. Among them, Potassium (K) has important functions related to the physiological processes in plant tissues, being the most extracted nutrient by sugarcane crop. Due to low natural K contents in tropical soils, it is necessary to complement it with fertilizer applications in order to meet the crop demands and achieve high yields. Therefore, the objective of this study was to evaluate the dynamics of potassium in the soil-plant system during the first sugarcane ratoon period as a function of potassium nutrition under the Cerrado of Goias edaphoclimatic conditions. The experiment was conducted at the Goiasa Plant, in Bom Jesus de Goiás, GO, during the 2017/18 season, in a dystrophic RED LATOSOL, clayey texture (440 g clay kg-1), using the variety IAC 91-1099. Treatments consisted of five K2O rates, (0 (control), 50, 100, 150 and 200 kg K2O ha-1), with five replicates. We evaluated: the climatic water balance for the area; the soil (up to 0.8 m) and plant K content (leaf and stem); biometric variables (plant height, stem diameter, number of tillers and leaf area); physiological variables (photosynthesis, transpiration, stomatal conductance, internal CO2 concentration and relative chlorophyll index); stem yield and technological quality. Also, decomposition rate and K release by the sugarcane straw as well as K balance in the soil-plant system were evaluated. Data were submitted to analysis of variance, and polynomial regression analysis was performed for the significant variables. The increase in Potassium fertilizer rate intensified the movement of the K+ ion in soil to the depth of 0.80 m with a 55% increase in K content between the control treatment and the 200 kg K2O ha-1 rate, in an evaluation performed at 180 days after sprouting, and a 20% increase at the end of the experiment. Sugarcane straw provided 79.25 kg K ha-1 to the soil, requiring approximately 70 days so 50% of this total would be available. There was a reduction of about 49.03% in straw production over 300 days, requiring 345 days so half of this material would decompose. K balance in the soil-plant system, for the annual application of 150 kg K2O ha-1 resulted in soil K balance of 133.22 kg ha-1 year-1, being the treatment that most contributed to increase soil K contents. Although the K rates in this experiment did not influence sugarcane growth, they presented a significant effect on physiological variables such as transpiration and photosynthesis. The higher K input in the soil as a function of the treatments did not result in differences in stem yield, however, when thinking about the sustainability of the productive system for sugarcane crops, the 150 kg K2O ha-1 rate increased soil K contents. / A cultura da cana-de-açúcar destaca-se como a fonte de energia renovável mais utilizada no Brasil apresentando elevada produtividade e boa adaptação às condições edafoclimáticas brasileiras. Devido à elevada produção de fitomassa, a extração de nutrientes do solo também é alta. Dentre eles, o potássio (K) apresenta funções importantes relacionadas aos processos fisiológicos no tecido vegetal, sendo o nutriente mais extraído pela cultura. Devido aos baixos teores naturais de K em solos tropicais torna-se necessário a sua complementação para atender a demanda da cultura para atingir altas produtividades. Diante disto, o objetivo deste estudo foi avaliar o efeito da adubação potássica na dinâmica de potássio no sistema solo-planta e seus impactos na produtividade, parâmetros fisiológicos e morfológicos da cana-de-açúcar em condições edafoclimáticas de Cerrado. O experimento foi conduzido na Usina Goiasa, em Bom Jesus de Goiás, GO, durante a safra 2017/18, em um LATOSSOLO VERMELHO distrófico de textura argilosa (440 g kg-1 de argila), utilizando a variedade de cana-de-açúcar IAC 91-1099. Os tratamentos foram constituídos por cinco doses de K2O, (0 (controle), 50, 100, 150 e 200 kg ha-1 de K2O), com cinco repetições. Avaliou-se: o balanço hídrico climatológico para área de estudo; o teor de K no solo (até 0,8 m) e na planta (folha e colmo); variáveis biométricas (altura da planta, diâmetro do colmo, número de perfilhos e área foliar), variáveis fisiológicas (fotossíntese, transpiração, condutância estomática, concentração interna de CO2 e índice relativo de clorofila); produção de colmos e qualidade tecnológica dos colmos. Ainda, foram avaliadas as taxas de decomposição e de liberação de K pela palhada de cana-de-açúcar e o balanço de K no sistema solo-planta. Os dados foram submetidos à análise de variância, procedendo-se analise de regressão polinomial para as variáveis significativas. O aumento da dose de fertilizante potássico intensificou a movimentação do íon K+ no solo até a profundidade de 0,8 m com aumento de 55% no teor de K entre o tratamento sem aplicação de K e com aplicação de 200 kg ha-1 de K2O, em avaliação realizada aos 180 dias após a brotação, e acréscimo de 20% ao final do experimento. A palha da cana-de-açúcar contribuiu fornecendo 79,25 kg ha-1 de K no solo, sendo necessário aproximadamente 70 dias para que 50% deste total fossem disponibilizados. Verificou-se uma redução de massa da palhada de cana-de-açúcar de aproximadamente 49,03% ao longo de 300 dias, sendo necessários 345 dias para que metade desse material se decomponha. O balanço de K no sistema solo-planta, para a aplicação anual de 150 kg ha-1 de K2O, resultou em um saldo de K no solo de 133,22 kg ha-1 ano-1, sendo a dose que mais contribuiu para aumentar as reservas do solo. As doses de K estudadas apesar de não exerceram influência sobre o crescimento da cana-de-açúcar, apresentaram efeito significativo sobre variáveis fisiológicas como transpiração e fotossíntese. O maior aporte de K no solo em função dos tratamentos não resultou em diferença na produtividade de colmos, no entanto, ao se pensar na sustentabilidade do sistema produtivo para a cultura, a dose de 150 kg ha-1 de K2O proporcionou maior incremento das reservas de K no solo.

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Une consommation élevée de sodium et une faible consommation de potassium sont associées à la survenue de l'HTA et des MCV. Limiter la consommation de sel et encourager celle de « plus de fruits et légumes » sont des mesures efficaces pour réduire l’incidence de ces maladies. Ces interventions nécessitent des données épidémiologiques fiables. Elles doivent aussi tenir compte de la disponibilité adéquate de l’iode dans le sel pour assurer un statut optimal en iode aux populations. Il n’existe pas de données représentatives sur le niveau de consommation en sodium, potassium et iode en population adulte au Bénin. Nos travaux ont estimé à partir de prélèvements urinaires les niveaux d’apports de ces éléments et la teneur en iode des sels alimentaires en utilisant les méthodes de références. Les résultats ont montré un apport excessif en sodium, faible en potassium, une légère déficience en iode et une iodation inadéquate de la production locale de sel. Les déterminants de ces différents apports ont été identifiés. Nous avons par ailleurs validé l’usage du spot urinaire pour le dosage du sodium et du potassium dans les études épidémiologiques et du spectrophotomètre (WYD Iodine Checker) pour le dosage de la teneur en iode du sel. L’ensemble des résultats plaident en faveur de la mise en œuvre urgente de politiques de réduction du sel et de promotion de fruits et légumes, et d’un renforcement du programme de lutte contre les TDCI au Bénin. / High sodium and low potassium consumptions are associated with increased blood pressure and cardiovascular diseases. Limiting salt and encouraging more fruits and vegetables are important interventions to reduce these diseases. These interventions need reliable epidemiological data. Interventions should also take into account the availability of adequate iodine in salt to ensure an optimal iodine status for populations. There is no representative data on sodium and potassium intakes and iodine status in Beninese adults. Our studies estimated, using urine samples, the levels of sodium, potassium and iodine intakes, and iodine content in food salts whith reference methods. Results showed an excessive intake of sodium, low potassium, a mild iodine deficiency and inadequate iodination of local salt production. Factors associated with these intakes have been identified. Results also validated the use of spot urine to assay sodium and potassium in epidemiological studies and spectrophotometer (WYD iodine checker) for iodine content in salt. All the results argue for implementation of salt reduction policies and promotion of fruits and vegetables, and a strengthening of the Beninese program against IDD.

The sustainability of production is widespread and discussed within the productive systems, resource utilization of the productive chain of the agricultural sector, mainly inputs, requires constant evaluations, since their socio-economic and environmental impacts may be irreversible. Potassium is the second nutrient requirement in terms of the cultures, in countries such as Brazil becomes evident, the growing demand for this element, however, more than 90% of the raw material for the manufacture of potash fertilizers is imported. Because to the large variability of existing soils, and different physicochemical properties of the minerals fertilizers in relation with the environment, parameters for fertilizer recommendations are based on physical and chemical properties of the soil, and sufficiency levels, within which it is possible to quantify and qualify the ability to release soil nutrients for plants. Several experiments with potassium, agronomically significant response is observed only at doses similar to the amounts exported by crops. This Work aims to improve and maximize the utilization of potassium added, so that will include technical and economic aspects, productivity and ensure a satisfactory integrated restricting the indiscriminate use of potash fertilizers, thus confirm or discard the following hypotheses. 1) Is added potassium recovered plants so, the fixing of this element into soil does not at significant levels. 2) Addition of K2O doses of higher levels existing in the soil increase the availability of potassium for plants stimulating the absorption enough above the limits for a given production. 3) The critical levels indicated as basis for recommendation are unnecessary; the addition of potassium can be based only on the need for certain crop yields. The study consisted of two experiments, so first occurred in the field, with two successive crops of soybean and wheat, on a Typic Hapludalf (EMBRAPA, 2006), located next to the department of soils, Federal University of Santa Maria (Universidade Federal de Santa Maria UFSM), in Santa Maria, RS, Brazil, with a history of potassium fertilization from 1991, the second were held in a greenhouse, and was based, soil samples collected in the area of the first experiment, and samples of an Typic Oxisol (EMBRAPA, 2006), coming from the Embrapa/Soy (Embrapa/soja) Londrina, PR, Brazil, also with a history of potassium fertilization from 1983. In both experiments the experimental units vary, as the initial content of potassium in the soil, and the amount of K2O added. / A sustentabilidade da produção é amplamente difundida e discutida dentro dos sistemas produtivos, a utilização dos recursos da cadeia produtiva do setor agrícola, principalmente insumos, necessita de avaliações constantes, uma vez que seus impactos sócio-econômicos e ambientais podem ser irreversíveis. O potássio é o segundo nutriente em termos de exigência pelas culturas, em países como o Brasil torna se evidente, a crescente demanda desse elemento, porém, mais de 90% da matéria prima para a fabricação de fertilizantes potássicos é importada. Devido à grande variabilidade de solos existentes, e às diferentes propriedades físico-químicas dos minerais fertilizantes em relação ao meio, os parâmetros para recomendação de fertilizantes baseiam-se em propriedades físicas e químicas do solo, e níveis de suficiência, dentro dos quais é possível quantificar e qualificar a capacidade de liberação de nutrientes do solo para as plantas. Vários experimentos com potássio têm observado resposta agronomicamente significativa apenas nas doses similares a quantidade exportada pelas culturas. O presente trabalho tem como objetivo melhorar e maximizar o aproveitamento do potássio adicionado, de maneira que venha a contemplar aspectos técnicos e econômicos, e garantir uma produtividade satisfatória integrada à restrição do uso indiscriminado de fertilizantes potássicos, desta forma, comprovar ou descartar as seguintes hipóteses: 1) O potássio adicionado é recuperado pelas plantas de tal forma, a fixação deste elemento pelo solo não ocorre em níveis significativos. 2) A adição de doses de K2O sobre teores mais elevados já existentes no solo aumenta a disponibilidade de potássio para as plantas, estimulando a absorção acima dos limites suficientes para determinada produção. 3) Os níveis críticos apontados como base para recomendação são desnecessários, e a adição de potássio pode se basear apenas na necessidade das culturas para determinadas produtividades. O trabalho constituiu-se de dois experimentos. O primeiro ocorreu no campo, com dois cultivos sucessivos de soja e trigo, sobre um Argissolo Vermelho distrófico típico (EMBRAPA 2006), localizado junto ao departamento de solos da Universidade Federal de Santa Maria, Santa Maria, RS, Brasil, com histórico de fertilização potássica a partir de 1991, e o segundo transcorreu em casa de vegetação, e teve como base, amostras de solos coletadas na área do primeiro experimento, e amostras de um Latossolo Vermelho distrófico típico (EMBRAPA, 2006) oriundo da Embrapa/Soja Londrina, PR, Brasil, também com histórico de adubação potássica, desde 1983. Em ambos os experimentos as unidades experimentais variam, quanto ao teor inicial de potássio no solo, e a quantidade de K2O adicionada.

M.Sc. (Botany) / Wheat is the second most important grain crop produced in South Africa. It is mostly used for human consumption (e.g. biscuits, rusks, breakfast cereals, and bread) with the remainder being used as seed and animal feed. Wheat is also used for production of alcohol for ethanol, absorbing agents for adhesives, disposable diapers and industrial uses as starch on coatings (Department of Agriculture, Forestry and Fisheries, 2011). The leading wheat producing areas in South Africa since 1994 are the Western Cape (38 %), Free State (26 %) and Northern Cape (17 %) (Department of Agriculture, Forestry and Fisheries, 2011). There are two main classes of cultivated wheat, these are durum wheat (Triticum durum) that contributes 5 % and common or bread wheat (Triticum aestivum L.), which contribute 95 % of the world wheat production (Kiplagat, 2005). One of the major threats to wheat production in South Africa and other countries is the Russian wheat aphid (RWA), (Kurdjumov), (Diuraphis noxia, Hemiptera: Aphididae) (Brooks et al., 1994). In South Africa, the Russian wheat aphid was reported as a pest of wheat in 1978 in the Eastern Free State (Walters, 1980). In the beginning of the 1979 season, it was detected only in the Eastern Free State, but quickly spread to the Western Free State and parts of Lesotho. Infestations were also isolated in some areas of KwaZulu-Natal, North West and Gauteng Province (Walters et al., 1980). Aphids are soft bodied insects and are the most economically important phloem feeders impacting on plants (Dixon, 1985; Klingler et al., 2009). Aphids damage plants in four ways. Firstly, they ingest vital plant metabolites including large volumes of translocated sugars from the phloem sap, diverting energy from the plant and reducing yield. Secondly, they secrete saliva into the plant tissues while probing the layers of leaf to find the phloem, in some instances the secreted saliva is thought to be phytotoxic (Dedryver et al., 2010). The physical damage done to the leaf along with the toxic attributes of the saliva leads to localized necrosis in some aphid plant interactions (Klingler et al., 2009). Thirdly, aphids act as virus vectors and they can be transmitted in a non-circulative or circulative manner (Chen et al., 2012).