Nas últimas três décadas, o crescimento na demanda por biocombustíveis promoveu a expansão das culturas de cana-de-açúcar no Brasil e, consequentemente, o aumento no consumo de pesticidas. Diversas espécies de anfíbios estão sujeitas à exposição a pesticidas por ocorrerem dentro e ao redor de canaviais. Entretanto, mesmo avaliações de risco preliminares são inviabilizadas pela raridade de estudos ecotoxicológicos com espécies de anfíbios nativas. Esta dissertação propôs testar experimentalmente as hipóteses de que (1) os principais herbicidas utilizados na cultura de cana-de-açúcar no Brasil, embora desenvolvidos especificamente para o controle de ervas daninhas, são capazes de causar mortalidade em larvas de anfíbios (2) esta mortalidade se manifesta mesmo quando larvas de anfíbios são expostas a concentrações ambientalmente relevantes destes herbicidas (3) além de efeitos letais, a exposição de larvas de anfíbios a concentrações ambientalmente relevantes dos principais herbicidas utilizados na cultura da cana-de-açúcar no Brasil causa efeitos subletais em termos de crescimento, desenvolvimento, comportamento, imunocompetência, e atividade enzimática, e estes efeitos subletais podem ser importantes em influenciar o rendimento dos indivíduos. Foram utilizadas como modelo biológico larvas do leiuperídeo Physalaemus cuvieri e dos hilídeos Hypsiboas faber e Hypsiboas pardalis. As três espécies têm áreas de distribuição parcialmente coincidentes com a área de cultivo da cana-de-açúcar, sendo que as duas primeiras sabidamente ocorrem dentro de canaviais. Estas espécies foram expostas aos herbicidas glifosato, ametrina, 2,4-D, metribuzim e acetocloro, na forma de seus ingredientes ativos. Somados, estes herbicidas correspondem a ~2/3 do volume de herbicidas utilizados em importantes regiões produtoras de cana-de-açúcar; por sua vez, herbicidas constituem a maior parte dos pesticidas usados na cultura. Os experimentos de exposição aguda com P. cuvieri e H. pardalis demonstraram que todos os herbicidas testados são tóxicos a larvas de anfíbios, embora alguns deles apenas em concentrações bastante elevadas. Houve uma hierarquia relativamente clara na letalidade dos herbicidas testados (glifosato < metribuzim < ametrina < acetocloro). Uma comparação com os dados disponíveis da toxicidade dos mesmos herbicidas para outras espécies de anfíbios, e para outros animais aquáticos, sugere que as espécies testadas nesta dissertação tendem a ser relativamente robustas, e que, ao contrário de uma hipótese amplamente difundida, anfíbios não aparentam ser particularmente sensíveis a contaminantes. Os experimentos de exposição crônica procuraram simular cenários realistas de exposição ao manipular as doses mínimas (H. faber) e máximas (H. faber, H. pardalis) de aplicação recomendadas pelos fabricantes para o controle de ervas daninhas na cultura de cana-de-açúcar. Conforme esperado, um prolongamento da exposição induziu mortalidade em concentrações muito inferiores àquelas necessárias para causar efeito em exposição aguda. Glifosato, ametrina e acetocloro em doses ambientalmente relevantes induziram mortalidade significativa de larvas de anfíbios, ao menos para H. pardalis. Glifosato, 2,4-D e metribuzim retardaram significativamente o desenvolvimento de H. faber, enquanto que ametrina, testada apenas para H. pardalis, levou a uma diminuição no ganho de massa e no estágio de desenvolvimento final atingido pelas larvas. A atividade de AChE foi inibida pelo metribuzim em H. faber e estimulada pelo glifosato, ametrina e 2,4-D em H. pardalis; por sua vez, a atividade de GST, inalterada pela exposição a herbicidas em H. faber, foi estimulada pela ametrina e pelo acetocloro em H. pardalis. Nenhum composto induziu alterações significativas no perfil leucocitário. Herbicidas também tiveram efeitos comportamentais: a taxa de atividade de H. pardalis foi significativamente reduzida sob exposição à ametrina e ao acetocloro. Esta dissertação sugere portanto que a exposição a doses ambientalmente relevantes dos principais herbicidas utilizados em cultura de cana-de-açúcar no Brasil podem causar efeitos letais e subletais em larvas de espécies nativas de anfíbios. Alguns destes efeitos subletais, como uma diminuição nas taxas de atividade, de crescimento e de desenvolvimento, podem ter importantes consequências para o sucesso dos indivíduos por prolongar o período larval e assim aumentar o risco de dessecação em corpos d´água temporários e semi-permanentes. Estudos futuros devem buscar realismo adicional rumo a uma análise de risco da contaminação ambiental por herbicidas por meio de experimentos manipulando não apenas ingredientes ativos, mas também formulações comerciais, bem como interações dos contaminantes entre si e com outros estressores ambientais, calibrados por concentrações medidas em campo. / In the last three decades, the increasing demand for biofuels in Brazil favored the expansion of sugarcane and, as a consequence, an increase in the consumption of pesticides. Several species of amphibians are subject to pesticide exposure for occuring in or around sugarcane fields. However, a preliminary risk assessment of pesticide exposure is not possible due to the absolute scarcity of ecotoxicological studies with native amphibian species. This thesis proposed to test the hypotheses that (1) the main herbicides used in sugarcane crops in Brazil, although designed for weed control, cause mortality of amphibian larvae (2) this mortality manifests even when amphiban larvae are exposed to environmentally relevant herbicide concentrations (3) in addition to any lethal effects, exposure of amphibian larvae to environmentally relevant herbicide concentrations causes sublethal effects in terms of growth, development, behavior, immunocompetence, and enzimatic activity, and these effects may be important in influencing individual performance. We used as model system the leiuperid frog Physalaemus cuvieri and the hylid frogs Hypsiboas faber and Hypsiboas pardalis. The distributional ranges of these species partially overlap with the region of cultivation of sugarcane in the country, and the first two species are known to colonize waterbodies in or around sugarcane fields. These three species were exposed to glyphosate, ametryn, 2,4-D, metribuzin and acetochlor, presented as active ingredients. These herbicides account to ~2/3 of the volume of herbicides employed in an important sugarcane producing region in the country; herbicides correspond to the majority of pesticides used in this crop. Experiments of acute exposure of P. cuvieri and H. pardalis showed that all herbicides are toxic to amphibian larvae, albeit some of them only in very high doses. There was a relatively consistent ranking in lethality among the compounds (glyphosate < metribuzin < ametryn < acetochlor). A literature review suggests that the species tested tend to be relatively robust when compared to other amphibians and other freshwater animals, and that, contrary to a broadly disseminated hypothesis, amphibians do not seem to be particularly sensitive to contaminants. Experiments of chronic exposure aimed at simulating realistic scenarios of exposure by manipulating minimum (H. faber) and maximum application doses (H. faber, H. pardalis), as recommended by manufacturers for weed control in sugarcane fields. As expected, prolonged exposure induced mortality at much lower concentrations than those manipulated in the experiments of acute exposure. Environmentally relevant concentrations of glyphosate, ametryn and acetochlor induced significant mortality in larval amphibians, at least for H. pardalis. Glyphosate, 2,4-D and metribuzin significantly slowed development in H. faber, whereas ametryn slowed development and growth in H. pardalis. Herbicides also had behavioral effects: activity rates of H. pardalis were significantly reduced under exposure to ametryn and acetochlor. AChE activity was inhibited by metribuzin in H. faber but stimulated by glyphosate, ametryn and 2,4-D in H. pardalis; in turn, GST activity, which was not influenced by exposure to herbicides in H. faber, was stimulated by ametryn and acetochlor in H. pardalis. No herbicide induced significant changes in leukocyte profiles. In conclusion, this thesis suggests that exposure to environmentally relevant doses of the main herbicides employed in sugarcane fields in Brazil can cause lethal and sublethal effects on native species of larval amphibians. Some of these sublethal effects, including the decrease in activity, growth and developmental rates, may have important consequences for individual performance for extending the larval period and as such increasing the risk of dessication in temporary and semi-permanent ponds. Future studies should seek additional realism towards a risk analysis of the environmental contamination by herbicides through experiments manipulating not only active ingredients but also commercial formulations, as well as interactions among contaminants and other environmental stressors, calibrated by field-measured conditions.

Submitted by Anaclaudia Mattos Villalba (anaclaudiamattosvillalba@gmail.com) on 2016-04-06T20:49:01Z No. of bitstreams: 1 Dissertacao-Jessica-final-BAC.pdf: 955783 bytes, checksum: b36ccc57d26b96db3b9beaa77b009765 (MD5) / Approved for entry into archive by cleuza maria medina dos santos (cleuzamai@yahoo.com.br) on 2016-05-04T20:56:36Z (GMT) No. of bitstreams: 1 Dissertacao-Jessica-final-BAC.pdf: 955783 bytes, checksum: b36ccc57d26b96db3b9beaa77b009765 (MD5) / Made available in DSpace on 2016-05-04T20:56:36Z (GMT). No. of bitstreams: 1 Dissertacao-Jessica-final-BAC.pdf: 955783 bytes, checksum: b36ccc57d26b96db3b9beaa77b009765 (MD5) Previous issue date: 2015 / O uso de agrotóxicos vem aumentando nos últimos anos em decorrência da ampliação das áreas de plantio e presença de pragas mais resistentes. No Rio Grande do Sul / Brasil, as culturas de arroz são consideradas como as principais responsáveis pelo lançamento destes produtos nos corpos d’água, uma vez que o Estado concentra 61% da rizicultura irrigada do país. Dentre os herbicidas mais utilizados nestas plantações estão variações de Roundup® , cujo princípio ativo é o glifosato. O modo de ação do glifosato como herbicida consiste na inibição da EPSPS, uma enzima-chave envolvida na biossíntese de amionoácidos essenciais de vegetais. Apesar disso, alguns estudos têm demonstrado que o glifosato pode atingir diferentes espécies animais, consideradas como espécies não-alvo. Tendo em vista o exposto, o objetivo do trabalho foi determinar, comparativamente possíveis efeitos que as formulações à base de glifosato, Roundup Original® (RO), Roundup Transorb® (RT) e Roundup WG® (RWG), possam estar causando à peixes que habitam regiões onde estes herbicidas são lançados. Para tanto, foi feito um teste agudo de mortalidade utilizando-se as concentrações de 0,5, 1 e 5 mg.L-1 de glifosato, calculado a partir da sua concentração em cada formula, e escolheu-se aquela onde não houveram animais mortos para avaliação de parâmetros oxidativos e qualidade espermática de exemplares de Jenynsia multidentitata. Apenas na concentração de 0,5 mg.L-1 de glifosato não houve mortalidade em nenhuma formulação, entretanto, os resultados mostraram que acima desta, a RT provocou maior mortalidade. Quanto aos parâmetros oxidativos, houve um desequilíbrio entre as defesas antioxidantes e a geração de espécies reativas de oxigênio (EROs) com consequente dano no fígado dos peixes. Esta situação foi mais evidenciada nos animais expostos ao RO que apresentaram aumento de EROs e redução na capacidade antioxidante total às 24 h de teste o que se refletiu num aumento expressivo de lipoperoxidação (LPO) às 96 h. Com relação aos parâmetros de qualidade espermática, apenas as análises de motilidade, funcionalidade mitocondrial e integridade de DNA dos espermatozoides apresentaram-se sob efeito dos herbicidas, sendo a motilidade o parâmetro mais sensível, pois foi inibida pelo glifosato nas 3 formulações experimentais (RO, RT e RWG) em 24 e 96 h de exposição. Assim, podemos concluir que os herbicidas à base de glifosato causam danos à espécie de peixe J. multidentata, induzindo o estresse oxidativo e influenciando negativamente na reprodução por afetar a qualidade espermática dos machos. No que compete à análise comparativa das formulações, a RT parece ser a mais tóxica por provocar maior mortalidade, no entanto, quando em concentração não letal e ambientalmente relevante como é o caso de 0,5 mg.L-1 de glifosato, a RO, que contém maior quantidade dos chamados componentes “inertes”, provoca maior dano oxidativo, nos entanto as 3 formulações influenciam igualmente a qualidade espermática. / The use of pesticides has increased in recent years due to the expansion of planting areas and the presence of more resistant pests. In Rio Grande do Sul / Brazil, the rice crops are considered to be primarily responsible for the launch of these products in water bodies, since the state concentrates 61% of irrigated rice culture in the country. Among the most widely used herbicides in these plantations, are variations of Roundup®, whose active ingredient is glyphosate. The mode of action of glyphosate as an herbicide is the inhibition of EPSPS, a key enzyme involved in the biosynthesis of essential amionoacids in plants. Nevertheless, some studies have shown that glyphosate can achieve different animal species, considered as non-target species. In the view of the above, the purpose of this study was to determine comparatively the effects of the glyphosate-based formulations, Roundup Original® (RO), Roundup Transorb® (RT) and Roundup WG® (RWG), may be causing in fish that inhabit these regions where herbicides are released. For that, an acute mortality test was performed with 0.5, 1 e 5 mg.L-1 of glyphosate, calculated following its concentration in each formulation, and we chosen the one that did not cause mortalities in fish to evaluate oxidative parameters and sperm quality of Jenynsia multidentitata. Only at a concentration of 0.5 mg.L-1 of glyphosate, there was no mortality in any formulation, however, the results showed that above this, RT caused higher mortality. As for the oxidative parameters, there was an imbalance between antioxidant defenses and the generation of reactive oxygen species (ROS) with consequent damage in fish liver. This situation was more evident in animals exposed to RO, where was observed an increase in ROS and a decrease in total antioxidant capacity at 24 h of test, that reflected in a significant increase in LPO at 96 h. With respect to sperm quality, only the motility analysis, mitochondrial functionality and DNA integrity of sperm are presented under the effect of herbicides, being motility the most sensitive parameter because it was inhibited by glyphosate in the 3 experimental formulations (RO RT and RWG) at 24 and 96 h of exposure. In summary, we conclude that the glyphosate-based herbicides cause damage to the fish species J. multidentata, inducing oxidative stress and negatively influencing reproduction. As it is for the comparative analysis, the RT appears to be the most toxic since it causes increased mortality, however, when at non-lethal and environmentally relevant concentration such as 0.5 mg.L-1 of glyphosate, RO which contains higher amounts of components called "inert", causes increased oxidative damage, but the 3 formulations affects sperm quality in the same intensity.

Orientador: Egle Novaes Teixeira / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-04T21:38:08Z (GMT). No. of bitstreams: 1 Chiquetti_SamantaCristina_M.pdf: 1690523 bytes, checksum: b4f72708172063f6203927a0fe94b5cc (MD5) Previous issue date: 2005 / Resumo: Os agrotóxicos têm sido usados na agricultura, mundialmente, para proteger as plantações e solos do ataque de pragas. As formulações de agrotóxicos devem ser acondicionadas em embalagens seguras e adequadas a cada tipo de produto. Após o uso da formulação, as embalagens vazias, contaminadas com resíduo de agrotóxicos, devem ser descartadas de maneira correta e segura, sendo a forma recomendada, no Brasil, a tríplice lavagem. Neste trabalho foi avaliada a eficiência da tríplice lavagem realizada em embalagens de agrotóxicos enviadas à Central de Recebimento de Embalagens Vazias, em Piracicaba, São Paulo, através da análise dos quatro ingredientes ativos mais comercializados nesta região: glifosato, MSMA, ametrina e tebutiurom. Foram analisadas, 75 embalagens de glifosato, 72 de MSMA, 70 de ametrina e 104 de tebutiurom. Os resultados demonstraram que 34,67 % das embalagens com glifosato, 58,33 % das com MSMA, 75,71 % das com ametrina e 73,07 % das com tebutiurom estavam em não conformidade com a norma vigente, ou seja, com um resíduo remanescente acima de 0,01 %. Concluiu-se que as embalagens analisadas apresentaram elevada percentagem dos princípios ativos, indicando que as tríplices lavagens foram executadas em desacordo à forma recomendada / Abstract: Pesticide formulations have been used in agriculture worldwide to protect the crops and soils from the attack of any pest. These formulations must be stored in safe containers proper to each kind of product. After use, the empty containers contaminated with pesticide residues must be disposed correctly and safely by triple rinse, the technical legislation recommended in Brazil. The aim of this study is to evaluate the efficiency of the triple rinse in empty pesticide containers that had been sent to the Collection site in Piracicaba region, São Paulo, through the analysis of the four main active ingredients traded in this region: gliphosate, MSMA, amethrin and tebuthiuron. In total, 75 gliphosate containers, 72 MSMA containers, 70 amethrin containers and 104 tebuthiuron containers were examined. The results were 34,67 % of the tebuthiuron containers, 58,33% of the MSMA containers, 75,71 % of the amethrin containers and 73,07 % of the tebuthiuron containers examined presented non-conformity with the actual technical legislation, that is, with residues above 0,01 %. This study concluded that the containers examined presented a high per cent of residue and that the triple rinse has not been executed according to the recommended technical legislation / Mestrado / Saneamento e Ambiente / Mestre em Engenharia Civil

A contaminação ambiental por pesticidas é uma preocupação cada vez mais presente, como indicam estudos que detectam frequentemente estes compostos em água e solo, e visto a importância destes, faz-se necessário a compreensão do seu impacto em organismos não alvo. Dessa forma, o estudo da resposta adaptativa bacteriana a herbicidas vem de encontro com a necessidade descrita, além de fornecer novos dados a cerca da regulação metabólica na possível biotransformação destes compostos. Neste estudo, o sistema antioxidante foi alvo de análises para a compreensão de sua participação neste processo, além de evidenciar a regulação diferencial de isoenzimas em bactéria exposta à herbicida. Para tanto, inicialmente um estudo de biodegradação apontou que o isolado bacteriano Enterobacter asburiae SD1 é capaz de degradar s-metolachlor em cerca de 30% com 13 h de cultivo em meio mineral, na presença de 1,25 mM do herbicida. Porém, a biodegradação também ocorreu em meio de cultura com fonte de carbono alternativa ao s-metolachlor, o que juntamente com o crescimento diferencial entre os meios, sugeriu uma resposta fisiológica adaptativa à diferentes condições nas quais o herbicida estava presente. Conhecido em estudos de resposta global a estresse, o sistema antioxidante foi avaliado na presença do herbicida e em diferentes consituições de meio de cultura, o que culminou em vias preferenciais ativadas conforme as características dos meios. Na presença de somente s-metolachlor como fonte de carbono (meio mineral), a enzima glutation S-transferase foi ativada, mostrando prioridade no reconhecimento e metabolização do s-metolachlor. Já na presença de outras fontes de carbono, além do herbicida, as vias de combate ao estresse oxidativo, representadas pelas enzimas catalase (CAT), superóxido dismutase (SOD) e glutationa redutase (GR), foram ativadas primeiramente. Além disso, foi possível também avaliar a ativação diferencial das isoenzimas de CAT e SOD frente ao s-metolachlor, sendo que a isoenzima Mn-SOD merece destaque pela importância na resposta adaptativa, visto que a deleção do gene sodA (Mn- SOD), causou danos a membrana e desequilíbrio no trabalho cooperativo enzimático no combate às ERO\'s (espécies reativas de oxigênio). Finalmente, a integração dos diferentes níveis de um metabolismo na resposta do sistema antioxidante bacteriano foi mostrado através do estudo com a via de controle traducional formada pela proteína EF-P (elongation factor P). Esta proteína atua na fidelidade do processo de síntese de proteína, e a deleção do gene efp que a codifica, bem como outras proteínas envolvidas na ativação desta via, resultou no desequilíbrio celular, gerando estresse oxidativo, potencializado pela presença do herbicida paraquat. Este trabalho reúne resultados bastante relevantes para a compreensão do papel do sistema antioxidante bacteriano, em condições de estresse gerado pela presença de herbicidas, e oferece dados importantes referentes a integração e regulação de vias bioquímicas na ativação do sistema antioxidante, bem como para uma eficiente resposta adaptativa deste sistema. / The environmental contamination by pesticides is an increasing concern, as frequently showed in studies with detection of these compounds in water and soil. In fact, the understanding of pesticide effect on non-target organisms is necessary given the importance of pesticide and its sustentable use. The study of bacterial adaptive response to pesticide can show how the metabolic regulation happens, as well as provide new data about biotransformation of these xenobiotics. For this propose, firstly the biodegradation analyse showed the Enterobacter asburiae SD1 strain has capacity to degrade the s-metolachlor herbicide in around 30% of your initial concentration (1,25 mM), in 13 h of cultivation in mineral medium. However, the degradation was also observed on the presence of alternative carbon source, what suggests, together the differential growth, the bacteria can show an adaptive response to different conditions represented by the media constitution. The antioxidant system, a global sensor to stress, was evaluated in E. asburiae SD1 cultivated in different media, to see what is the effect of s-metolachlor herbicide in the antioxidant response. It was possible to observe preferential pathways activated according to medium characteristics, such as the activation of glutathione Stransferase in the presence of only s-metolachlor as carbon source. This result was explained by the bacterial need to recognize and metabolize a new molecule. On the other hand, in the presence of alternative carbon source, in addition to herbicide, the pathways to combat oxidative stress, as those constituted by catalase (CAT), superoxide dismutase (SOD) and glutathione reductase (GR), were firstly activated. Besides this, the differential activation was observed among the isoenzymes of CAT and SOD, wich special attention to Mn-SOD, which one had an important role in the adptive responde to herbicide. This affirmation was justified when de delection of sodA gene (Mn-SOD) induced membrane damage and disruption in the cooperative work of antioxidant enzymes in bacteria exposed to s-metolachlor. Finally, the integration of different levels of metabolism in the antioxidant response was showed through study with a pathway envolved in the translational control which has the elongation factor-P (EFP) as one important protein. This enzyme acts in the fidelity during the protein synthesis, and its absence, caused by efp gene delection, as well others two protein important to activate the EFP, induced the oxidative stress, increased by the paraquat herbicide. The present work collects relevant results for understanding of the role of bacterial antioxidant system in the stress condition induced by herbicide presence, and also offers important data about integration and regulation of biochemical pathway in the antioxidant system activation for an efficient adaptative response.

Master of Science / Department of Agronomy / Johanna A. Dille / Palmer amaranth and horseweed are problematic weeds in no-till soybeans in Kansas. Integrating cover crops and herbicide programs could suppress weed populations. To determine the emergence pattern and survival of horseweed, a study was conducted across six locations in eastern KS in 2014-2015 and 2015-2016. Horseweed seedlings and leaf number per seedling were recorded at two-week intervals. Cumulative GDDs required to reach 50% horseweed emergence increased from north to south. Horseweed survival ranged from 4 to 90%, and majority of horseweed emerged in the fall. Field studies were conducted to determine effects of cover crops and herbicide programs on Palmer amaranth near Manhattan, KS in 2014-2015 and 2015-2016. Five cover crop treatments included no cover, fall-sown winter wheat, spring-sown oat, pea, and mixture of oat and pea. Cover crops were terminated in May with glyphosate and 2,4-D alone or with residual herbicides of flumioxazin and pyroxasulfone. By 10 weeks after termination in 2014-2015, Palmer amaranth biomass and density, averaged across cover crops. was 95 and 69% less with residual herbicides than without, respectively, and Palmer amaranth biomass was 98% less in winter wheat and 91% less in spring oat, averaged across termination methods, compared to no cover. Time to 50% Palmer amaranth emergence was delayed with winter wheat, spring oat, and spring oat/pea mix without residual herbicide. Soybean yields were greater with residual herbicide and greater with winter wheat or spring oat cover crop in 2014-2015. A field study was conducted to determine suppression effects of cover crop and herbicide programs on horseweed and Palmer amaranth near Manhattan, KS in 2015-2016. Three fall treatments included fall-sown rye, a residual herbicide tank mix of glyphosate, dicamba, chlorimuron-ethyl, tribenuron-methyl, and AMS, and no fall application. Four spring treatments included no spring application or three herbicide tank mixes: glyphosate, dicamba, and AMS alone or with flumioxazin and pyroxasulfone as early preplant, or as split applied with 2/3 preplant and 1/3 at soybean planting. Similar levels of horseweed suppression were observed when some control measure was used in fall or spring. Fall rye completely suppressed horseweed while the fall herbicide suppressed biomass by 93% and density by 86% compared to no fall application. Palmer amaranth suppression was observed when a spring herbicide application was used. In rye, total weed biomass was reduced by 97% or more across all spring treatments. Total weed biomass was reduced with a spring herbicide was used. Soybean yields were least when no herbicide treatment was used in the spring. An integrated program of fall cover crops or herbicide applications together with spring herbicide applications maintained soybean yields.

M.Sc. / Please refer to full text to view abstract

Gypsiferous water, i.e water containing high levels of calcium sulphate, is used to irrigate crops such as maize and wheat on a commercial scale, in some parts of South Africa due to shortage of irrigation water. Gypsiferous water is saline due to the presence of Ca2+, S042- and sometimes Mg2+ in solution. These salts may have a detrimental effect on herbicide performance. Possible herbicide injury to crops has been reported in areas irrigated with gypsiferous water, which suggested interaction between herbicides and gypsiferous water. Bioassay experiments were conducted in the greenhouse to assess whether the bioactivity and persistence of the selected herbicides were affected by the presence of gypsum in the soil. The biological activity of atrazine was significantly increased in the presence of gypsum, and in the case of 2,4-D the same effect was even more pronounced. In contrast, the activity of metolachlor was reduced in the presence of gypsum. These differential effects on herbicide activity would have important practical consequences for herbicide performance, i.e weed control efficacy, selectivity, and behaviour in soil. In the persistence experiment, the activity of all herbicides decreased with time. However, the presence of gypsum had a significant effect on the rate of dissipation of only atrazine. In the presence of gypsum the rate of loss of atrazine was significantly less compared to its rate of loss in soil that did not contain gypsum. The rate of loss of metolachlor was not significantly affected by the presence of gypsum, and in the case of 2,4-D the trends were not clear at all. A further experiment was conducted to determine the leaching potential of metolachlor and atrazine in soil irrigated with either gypsiferous water or uncontaminated water. In the leaching experiment metolachlor showed a significant growth reduction of 39% in the first 10 cm column zone in soil irrigated with gypsiferous water and no further losses were observed in deeper column segments, and this indicated that there would be no threat of groundwater contamination. However, the results showed that weeds with shallow roots would be effectively controlled in this column. Similar results were observed in soil without gypsiferous water irrigated. The findings of this experiment appear to contradict the findings of Chapter 4 for metolachlor, however it is to be considered that in Chapter 4 the "close system" was used and in the leaching experiment an "open system" was used. In addition, the calcium sulphate concentrations for the two experiments were different. In the atrazine experiment it was found that 0.1 mg kg-1 would pose a serious threat to groundwater contamination and sensitive follow-up crops. There is a need to reduce the atrazine dosage rate to 0.05 mg kg-1 because no threat to groundwater was observed at this rate. However, weed control efficacy at this low rate maybe poor. / Dissertation (MSc (Agric): Weed Science)--University of Pretoria, 2006. / Plant Production and Soil Science / unrestricted

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

MSc. (Geography) / Growing concerns with regards to the environmental and economic impacts related to the application of herbicides to control the spread and abundance of weeds in agricultural crops have created a need for the development of novel agricultural management systems that are less dependent on herbicide usage and tillage. Such concerns have given rise to the need for the variable spatial treatment of croplands aimed at the minimization of requirements for the application of herbicides and the subsequent minimization of excess materials released into the surrounding environment. Remote sensing provides an opportunity for the fast and cost-effective delineation of weed patches in croplands over large areas where traditional scouting techniques would be impractical. The differences in spectral reflectance from different plants at certain wavelengths due to species specific variations in biochemical and physical characteristics is what lays the basis for the distinction of vegetation species within remotely sensed images and ultimately the potential detection of weed-species in croplands. This study investigates the potential spectral characterisation of maize and commonly occurring weed-species by (1) making use of reflectance spectra collected at leaf-level to identify statistically significant differences in reflectance between individual species throughout the visible (VIS), Near-Infrared (NIR) and Shortwave-Infrared (SWIR) regions of the electromagnetic spectrum, determining the potential of the Red-Edge Position (REP) and slope for this particular application and testing the accuracy at which reflectance spectra may be classified according to vegetation species based on spectral reflectance at specific wavebands and REP as input predictor variables, (2) testing the potential effect of mixed spectral responses and soil-background interference through the analysis of reflectance spectra collected at canopy-level, and (3) determining the potential effect of the spectral generalisation associated with multispectral reflectance through the analysis of spectral responses resampled to the spectral band designations of representative high spatial resolution multispectral sensors. The results showed that maize may be spectrally distinguished from all of the weed-species included in the analysis based on leaf-level hyperspectral reflectance throughout the Visible-to-Near-Infrared (V-NIR) and SWIR-regions of the electromagnetic spectrum, however, the unique characterisation of weed-species is not possible for all species and where it is possible, it is highly wavelength-specific and would require high spectral resolution hyperspectral data. The wavelengths most suitable for the spectral characterisation of maize-crops and weed species in the study area were identified as: 432.1nm, 528.2nm, 700.7nm, 719.4nm, 1335.1nm, 1508.1nm, 2075.8nm, 2164.5nm and 2342.2nm. The output predictor model was able to classify reflectance spectra associated with maize crops and weeds in the study area at an overall accuracy of 89.7 per cent and it was shown that the inclusion of the REP as predictor variable did not improve the overall accuracy of the classification, however, may be used to improve the classification accuracies of certain species...

Orientador: Cassiana Maria Reganhan Coneglian / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Tecnologia / Made available in DSpace on 2018-08-22T10:59:00Z (GMT). No. of bitstreams: 1 Rego_AnaPaulaJustiniano_M.pdf: 1374824 bytes, checksum: f4374ed0d3dafb4fb76f0bd4a5678bc9 (MD5) Previous issue date: 2013 / Resumo: A ametrina é um herbicida utilizado em culturas de cana-de-açúcar no período de pré e pós emergência das plantas daninhas. É um composto persistente no meio ambiente, podendo lixiviar para água subterrânea e escoar para águas superficiais, provocando impacto na comunidade aquática. No presente trabalho avaliou-se a atividade microbiana em solo com histórico de aplicação da ametrina em cultivo de cana de açúcar, acrescidos de concentrações de solução de ametrina e biofertilizante comercial Microgeo. Coletaram-se três amostras de solo em área de cultivo de cana de açúcar, sendo o primeiro solo caracterizado como argiloso, o segundo arenoso, o terceiro arenoso, mas esterilizado em estufa a 106ºC. As concentrações utilizadas da ametrina nos experimentos foram de 8 e 12 ?g/mL e, as de biofertilizante foram 1, 5 e 10%. Para avaliar a atividade microbiana do solo utilizou-se o método respirométrico de Bartha que quantifica a geração de CO2 em mg/L e após o processo de biodegradação o método enzimático de hidrólise de FDA para avaliar a estimativa da atividade microbiana. Quantificou-se a população de bactérias heterotróficas e fungos expressos em UFC/g de solo antes e após o experimento de respirometria. Realizou-se teste de toxicidade com o organismo-teste Daphnia similis exposta ao herbicida ametrina nas concentrações 0,01; 0,1; 1; 10 e 100 ?g/L, do biofertilizante nas concentrações 1, 10 e 100% e do solo antes e após o experimento de respirometria, utilizando a fração solúvel. Realizou-se teste de fitoxicidade com a semente Lactuca sativa antes e após os experimentos de respirometria, utilizando a fração solúvel do solo. De acordo com os resultados obtidos pode-se concluir que a produção de CO2 foi maior em solo arenoso e menor em solo argiloso e em solo estéril. A estimativa microbiana pelo método de FDA foi maior em solo argiloso e arenoso e menor em solo estéril. O herbicida ametrina apresentou toxicidade ao organismo Daphnia similis. Antes e após os experimentos de respirometria, o solo não apresentou efeitos tóxicos à Daphnia simillis, não sendo possível calcular o CE50. Os solos antes e após experimentos de respirometria não apresentaram inibição na germinação e alongamento das raízes de Lactuca sativa. Conclui-se que o herbicida ametrina como citado na literatura é lentamente biodegradado no solo e a adição de biofertilizante Microgeo não corroborou com a sua biodegradação, mas favoreceu a atividade microbiana do solo / Abstract: The ametryn is an herbicide used on crops of sugar cane in the pre and post emergence weed. It is a compound persistent in the environment and can leach into groundwater and surface water to drain, causing impact on the aquatic community. In this study we evaluated the microbial activity in soil with a history of application of ametryn in cultivation of sugar cane, plus concentrations of ametryn solution and commercial bio fertilizer Microgeo. Three samples were collected from soil in sugar cane cultivation area, the first being characterized as clayey soil, the second sandy, and the third gritty but sterilized in an oven at 106 °C. The concentrations used in the experiments of ametryn were 8 and 12 ?g / mL, and the bio fertilizers were 1, 5 and 10 %. To evaluate the microbial activity in the soil it was used the Bartha respirometric method that quantifies the CO2 generation in mg / L and after the biodegradation the process of the enzymatic hydrolysis of FDA to evaluate the estimation of microbial activity. We quantified the population of heterotrophic bacteria and fungi expressed in CFU / g of soil before and after the respirometry experiment. We held a toxicity test with the Daphnia similis organisms test exposed to herbicide ametryn at 0.01, 0.1, 1, 10 and 100 mg/L of bio fertilizer concentrations 1, 10 and 100% and soil before and after the respirometry experiment, using the soluble fraction. A test of fitoxicity was performed with Lactuca sativa seed before and after the respirometry experiments using the soluble fraction of the soil. According to the obtained results it can be concluded that the CO2 production was higher on sandy soil and smaller in clayey soil and sterile soil. A method for estimating microbial FDA was higher in clay soil and sandy soil and lower in sterile. The herbicide ametryn showed toxicity to the organism Daphnia similis. Before and after the respirometry experiments, the soil showed no toxic effects to the Daphnia simillis, it is not possible to calculate the EC50. The soils, before and after respirometry experiments showed no inhibition on seed germination and root elongation of Lactuca sativa. It is concluded that the herbicide ametryn as quoted in the literature is slowly biodegraded in soil and the addition of the bio fertilizer Microgeo has not substantiated its biodegradation, but favored the soil microbial activity / Mestrado / Tecnologia e Inovação / Mestre em Tecnologia