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

Doctor of Philosophy / Department of Agronomy / Dorivar Ruiz Diaz / Winter annual weeds (WAW) could affect nitrogen supply for corn production. The objectives of first study were to determine the diversity and abundance of WAW and to evaluate the effect of delaying herbicide applications on nitrogen supply and no-till corn response. Research was conducted in 2010 and 2011 at 14 sites in eastern Kansas. A factorial arrangement of three herbicide application dates (Nov.-Mar., April, and May) and five N rates were used. The three most abundant WAW across sites were henbit, purslane speedwell, and horseweed. Delaying herbicide application until April significantly reduced early corn N uptake by 52 mg N plant-1, chlorophyll meter readings at silking by 3.4%, and grain yield by 0.48 Mg ha-1 across sites. An additional 16 to 17 kg N ha-1 was needed to maintain yield if herbicide application was delayed until April. Starter and foliar micronutrient fertilization can potentially increase corn and soybean yield. The objectives of the second study were to evaluate crop response from combinations of starter and foliar fertilizers that contain N-P-K mixtures with and without a blend of micronutrients at four sites for each crop under irrigated conditions. No early corn growth or yield increase was attributed to application of micronutrients (Fe, Mn, Zn, Cu, and B) beyond what was achieved with N-P-K starter fertilization. There was an increase in soybean height (8 cm) and yield (293 kg ha-1) with starter fertilizer containing N-P-K plus micronutrients over the control. No increase in corn or soybean yield was obtained with foliar fertilization. The objective of the third study was to compare soil mobility and changes in soybean nutrient concentration in the leaf and seed from Mn and Zn sources (EDTA and oxysulfate) at two sites. Zinc sources were more mobile in the soil. Both Zn sources increased seed Zn concentration. Manganese oxysulfate increased seed Mn concentration. However, soybean trifoliolate leaf and seed Mn concentration decreased with soil-applied Na2EDTA and MnEDTA. This response was attributed to formation of FeEDTA and increased Fe supply that reduced root Mn absorption. Manganese EDTA is not recommended for soil application.

The diploma thesis deals with harrowing of spelt wheat (Triticum spelta L.) by the weeding harrows and its influence on weed frequency, yield and quality parameters of wheat. In the literature review there are described general cultivation principles for the growing of spelt (Triticum spelta L.) used in current agricultural practice. There is overview of the general principles of spelt wheat cultivation in the organic farming, available varieties in the Czech Republic and brief description of agricultural technology suitable for its cultivation. We also describe the types of weeds, their brief description and the possibility of reducing their frequency in the organic farming growing system. The literature review provides also information about the technology of harrowing cereal crops as a measure to control weeds and other positive aspects of harrowing on grain crops. In the practical part, data from a field trial were collected, where the effect of harrowing on the weed frequency, the influence of harrowing on spelt wheat tillering and other parameters were statistically evaluated and compared with results in the literature. At the end of the thesis, given the results evaluated in the practical part, it was determined whether it is appropriate to use harrowing as protection of spelt wheat (Triticum spelta L.), its number, influence on weed infestation and its influence on both the quantitative and qualitative properties of spelt wheat (Triticum spelta L.).

<p>Maize is a major calorie source for people living in Sub-Sahara Africa. In this region, <i>Aspergillus flavus</i> causes ear rot diseases in maize, contributing to food insecurity due to aflatoxin contamination. The biological control principle of competitive exclusion has been applied in both the United States and Africa to effectively reduce aflatoxin levels in maize at harvest by introducing atoxigenic strains that out-compete toxigenic strains. The goal of this study was to determine if the efficacy of preharvest biocontrol treatments carry over into the drying period, which is often delayed in Sub-Sahara Africa by the complexities of postharvest drying practices and lack of modern drying machinery. Maize was collected from fields in Texas and North Carolina that were treated with commercial biocontrol, and control fields that were untreated. To simulate moisture conditions similar to those experienced by farmers during drying in Sub-Sahara Africa, we adjusted the grain to 20% moisture content and incubated it at 28 ℃ for 6 days. Although the initial number of infected kernels in most samples were high, less than 24% of kernels were infected with <i>Aspergillus flavus</i> and aflatoxin levels were low (<4ppb). Both toxigenic and atoxigenic strains increased and spread through the grain over the incubation period, and aflatoxin levels increased, even in samples from biocontrol-treated fields. Our molecular analysis suggests that applied biocontrol strains from treated fields migrate to untreated fields. The results also indicate that the population of toxigenic <i>A. flavus</i> in the harvested grain will grow and produce aflatoxin during the drying period when moisture is high. Therefore, any potential postharvest reduction in aflatoxin accumulation will depend on how effective the biocontrol strain was at displacing the toxigenic populations prior to harvest.</p>

MSc., Faculty of Science, University of the Witwatersrand, 2011 / The behaviour and physiology of every insect, during all developmental stages, is largely determined by temperature. Metabolic rate, flight activity, nutrition, growth rate, oviposition and longevity can all be correlated to temperature. Consequently, insect development occurs within a definite temperature range which can be experimentally determined. This serves as a basis from which models that estimate insect growth, development and reproduction can be formulated. Such studies on temperature-dependent development are therefore important for understanding predator-prey relationships and insect population dynamics relevant in epidemiology, pest management and biological control of weeds and insect pests. The biological control of water hyacinth, Eichhornia crassipes (Pontederiaceae), in South Africa currently relies on six established agents. However, the results of this programme do not compare well with the achievements made elsewhere. This has been attributed to a number of constraining factors, chief among which is a wide variety of climatic regions, low minimum temperatures and a high incidence of frosting which slows the build-up of natural enemy populations. This research verified and augmented the thermal tolerance data available for three of South Africa’s more efficacious agents used against water hyacinth, namely Neochetina eichhorniae, N. bruchi (Curculionidae) and Eccritotarsus catarinensis (Miridae). Using these data, plant productivity and insect activity was modelled against fine-scale temperature data incorporating three distinct microclimates from 14 field sites distributed throughout South Africa’s climatic regions. Water hyacinth and its natural enemies were found to be negatively affected by low average temperatures. However, the relative consequences for each species at a population level were quite different. Similar thresholds for development, close to 10°C, meant that periods available for growth in areas where temperature is limiting were roughly the same for both plant and insects. Nevertheless, although plant growth largely ceased each winter and aerial parts were often extensively damaged from frost, low temperatures rarely led to significant plant mortality. By contrast, reduced insect recruitment coupled with a high susceptibility to cold- and frost-induced mortality of all life-history stages, pushed insect populations into winter bottlenecks and even caused local extinctions. The ability to overwinter effectively appears to the primary cause for limited control in colder regions. Surviving post-winter insect populations were therefore small, inflicted minimal damage due to reduced feeding rates, and were generally asynchronous with the recovery of water hyacinth. This asynchronous development translated into a lag period of roughly 42 days between the onset of water hyacinth growth and the time at which the plant was subjected to meaningful herbivory. Free from early season herbivory, coupled with the fact that vegetative reproduction continued through winter, water hyacinth populations were able to quickly recover and outpaced the detrimental affects caused by insect feeding well into the growth season. The implications for supplementary management strategies are also discussed in light of these outcomes.

Resumo: O presente trabalho teve como objetivo avaliar a quantidade e qualidade da deposição da calda de pulverização em plantas de feijão, Bidens pilosa L. e de Brachiaria plantaginea (Link) Hitch, presentes na linha e entrelinha da cultura, além da deposição no solo, em aplicações de pós-emergência. Foi utilizado como traçador o corante Azul Brilhante FDC -1 na concentração de 500 ppm. Os tratamentos constituíram de 3 modelos de ponta de pulverização, jato plano (XR 110015 VS e XR 11002 VS), jato plano duplo (TJ60 11002 VS) e jato cônico (TXVS 6 e TXVS 8); e dois volumes de aplicação 150 e 200 L ha-1, respectivamente. Utilizou-se o delineamento em blocos ao acaso, com 4 repetições. Os resultados dos dados quantitativos de deposição foram analisados nos seguintes esquemas em fatorial: para os depósitos em plantas de feijão foi utilizado o esquema 3 x 2 (3 modelos de pontas de pulverização x 2 volumes de aplicação); para as plantas daninhas presentes na linha e na entrelinha da cultura do feijão, o esquema foi 3 x 2 x 2 (3 modelos de pontas de pulverização x 2 volumes de aplicação x 2 espécies de plantas daninhas); para as estimativas de deposição no solo, o esquema foi 3 x 2 x 2 (3 modelos de pontas de pulverização x 2 posições (linha e entrelinha) x 2 volumes de aplicação). Foram amostradas 25 plantas por repetição em cada parcela, tanto para as plantas de feijão quanto para as plantas daninhas presentes na linha e na entrelinha da cultura. Após a aplicação, as plantas foram imediatamente coletadas, e em seguida foram lavadas em 100 mL de água destilada para posterior quantificação do traçador em espectrofotômetro. Para as analises qualitativa, cada planta selecionada ao acaso dentro da faixa de aplicação da barra foi considerada uma repetição, o que representou um total de 100 repetições. Os dados obtidos foram... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The present work had as objective to evaluate the amount and deposition quality of spray solution in common bean plants, Bidens pilosa L. and Brachiaria plantaginea (Link) Hitch, current in the crop row and spacing row, beyond the deposition in soil, in applications of post-emergency. It was used the brilliant blue FDC - 1 as tracer solution, with 500 ppm. The treatments had constituted of 3 models of spray nozzles, flat fan nozzle (XR 110015 VS and XR 11002 VS), double flat fan nozzle (TJ60 11002 VS) and cone nozzle (TXVS 6 and TXVS 8); and two application volumes 150 and 200 L ha-1, respectively. It was used a randomized blocks design, with four replications. Being that, the results of the quantitative data of deposition had been analyzed in following factorial schemes: for the deposits in common bean plants was used 3 x 2 factorial scheme (3 models of spray nozzle x 2 application volumes); for the weeds in the common bean crop row and spacing row, the factorial scheme was 3 x 2 x 2 (3 models of spray nozzle x 2 application volumes x 2 weed species); for the soil deposition estimates, the factorial scheme was 3 x 2 x 2 (3 models of spray nozzle x 2 positions (row and spacing row) x 2 application volumes). Were sampled 25 plants for replication in each plot, as much for the common bean plants as current weeds in crop row and spacing row. After application, the plants were immediately collected, and after they had been washed in 100 mL of distilled water for posterior tracer quantification in spectrophotometer. For the quantitative analysis, each random selected plant inside of boom application stripe bar was considered a replication, representing a total of 100 replications. The obtained data had been adjusted a regression curve for Gompertz model. The results had evidenced that: (i) the biggest deposits of spray solution in soil had occurred in the crop spacing row, independent of the... (Complete abstract click electronic access below) / Orientador: Dagoberto Martins / Coorientador: Fernando Tadeu de Carvalho / Banca: Carlos Gilberto Raetano / Banca: Mario Sergio Tomazela / Mestre

Orientador: Pedro Luís da Costa Aguiar Alves / Banca: Robinson Antônio Pitelli / Banca: Ricardo Victória Filho / Resumo: A interferência das plantas daninhas pode prejudicar o desenvolvimento de culturas em ecossistemas agrícolas, comprometendo a produtividade e a qualidade do produto colhido. Estudos ecológicos das comunidades infestantes e o conhecimento do período de interferência podem auxiliar no desenvolvimento de programas de manejo das plantas daninhas. Desta forma, o objetivo deste trabalho foi estimar os períodos de interferência das plantas daninhas na cultura do grão-de-bico, em resposta a doses de cobertura de nitrogênio e realizar o levantamento florístico e fitossociológico de comunidade infestante da área. Nos anos de 2011 e 2012 foram conduzidos três experimentos utilizando doses de nitrogênio em cobertura (0, 50 e 75 kg N ha-1), aos 40 dias após a semeadura do grão-de-bico. Os experimentos foram conduzidos utilizando períodos crescentes (0, 7, 14, 21, 28, 35, 42, 56, 63 e 140 dias após a emergência) de convivência e controle de plantas daninhas na cultura do grão-de-bico em duas situações: inicialmente livre das plantas daninhas (LPD) e inicialmente infestado pelas plantas daninhas (IPD). Os períodos de interferência das plantas daninhas sobre o grão-de-bico foram baseadas nas perdas de produtividade ao longo do tempo. Os levantamentos florísticos e fitossociológicos foram realizados ao término de cada período de convivência da cultura com as plantas daninhas (períodos IPD) e aos 70 dias após a emergência para o grupo de períodos crescentes de controle das plantas daninhas (LPD70), utilizando três quadrados de 0,25 m2 por parcela para o estudo florístico e fitossociológico. As plantas daninhas interferiram negativamente na produtividade do grão-de-bico, causando perdas de rendimento. Os períodos críticos de interferência, nos experimentos adubados com 50 e 75 kg N ha-1 (entre 5 a 65 dias após a emergência em... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Weeds can cause several interferences on the development of crops in agricultural ecosystems, affecting mainly the productivity and the quality of the harvested product. Ecological studies of weed communities and the knowledge of periods of weed interference on crops may assist in developing programs for weed management. The aims of this study were estimate the periods of weed interference in the chick-peas corp, grown under different concentrations of nitrogen topdressing and evaluate the flora and phytosociology of the weed community in this area. During the 2011 and 2012 harvests we conducted three experiments in each year, using the nitrogen topdressing concentrations at 0, 50 and 75 kg N ha-1 at 40 days after sowing the crop. The experiments were conducted using increasing periods (0, 7, 14, 21, 28, 35, 42, 56, 63 and 140 days after emergence) of coexistence and control weeds in chick-peas and weeds in two situations: initially weed-free (WF) and initially weed-infested (WI) periods. The determinations of the weed-period interferences on chick-peas were performed based on loses of productivity over time. The floristc and phytosociological surveys were conducted at the end of each period of coexistence among the crop and the weeds in all WI periods and at 70 days after emergence for the period WF70 using three squares 0,25 m2 per plot for floristic and phytosociological studies. Weeds negatively interfered on chick-peas productivity, causing yield losses. The critical weed-interference periods for the experiments with 50 and 75 kg N ha-1 (5-65 DAE in 2011 and 10-61 in 2012 accepting 5% of losses), remained close the times the experiment without nitrogen topdressing (0 kg N ha-1) (7-76 days after emergence in 2011 and 11-64 in 2012 accepting 5% of losses). The nitrogen topdressing increased... (Complete abstract click electronic access below) / Mestre

Orientador: Teresa Cristina Tarlé Pissarra / Coorientador: Marcelo da Costa Ferreira / Banca: Rouverson Pereira da Silva / Banca: Carlos Alberto Mathias Azania / Resumo: A manutenção da produtividade e rentabilidade da cana-de-açúcar (Saccharum spp) é dependente o uso de herbicidas. Pesquisas relacionadas à qualidade da aplicação de herbicidas em função da largura da barra de pulverização, condições meteorológicas e declives em áreas sistematizadas para mecanização agrícola da cultura ainda são escassos. Tem-se a hipótese que a sistematização de terrenos pode favorecer o uso de barras de maior largura, independentemente das condições meteorológicas encontradas no momento da aplicação e da declividade. O objetivo deste trabalho foi avaliar a cobertura e o depósito de calda herbicida em função da largura da barra de pulverização, do gradiente de declividade e das condições meteorológicas em área de cana com plantio sistematizado. O delineamento experimental utilizado foi em blocos casualizados em esquema fatorial 2 x 2 x 2, em quatro repetições. Os níveis dos fatores foram constituídos pelo resultado da combinação da largura da barra de pulverização (15 e 27 m), declividade do terreno (0 a 5% e 5,1 a 10%) e condições meteorológicas (recomendadas e adversas). Os dados foram submetidos ao teste F da análise de variância (ANOVA) e quando houve significância as médias das parcelas foram comparadas entre si, utilizando-se o teste de Tukey a 5% de probabilidade. A cobertura de gotas foi superior com a barra de pulverização de maior largura, em maior declive e em condições meteorológicas recomendadas. Quanto ao depósito de calda sobre os coletores artificiais, houve deposição superior com a barra de largura maior e sob condições meteorológicas recomendadas. Porém, houve efeito significativo da declividade nos valores de depósito sobre o alvo / Abstract: Maintaining the productivity and profitability of sugarcane crops (Saccharum spp) depends on the use of herbicides. Research related to the quality of herbicides application by the width of the spray boom, weather and terrain declivity in path planning areas for agricultural mechanization of sugarcane are still unclear. It has been hypothesized that the path planning areas can favor the use of larger width spray booms, regardless of weather conditions found at the time of application and the declivity. Here we evaluate the coverage and uptake by spraying herbicide in sugarcane crop due the spray boom size, terrain declivity and weather condition. The experimental design was a randomized block in a factorial 2 x 2 x 2, with four replications. The factor levels were made by combining the result of the spray boom width (15 and 27 m), terrain declivity (0 to 5% and 5,1 to 10%) and weather condition (recommended and adverse). The data were submitted to F test analysis of variance (ANOVA) and the means of the plots were compared using the Tukey test at 5% probability. The coverage of droplets was higher with the bigger spray boom, on upper declivity and under weather condition recommended. About the deposition on the artificial collectors, uptake was higher using the spray boom more width and under weather condition recommended. Otherwise, there was a significant effect of declivity on spray deposit values over the artificial targets / Mestre

Orientador: Pedro Luís da Costa Aguiar Alves / Coorientador: Mariluce Pascoina Nepomuceno / Coorientador: Kumudini M. Meepagala / Banca: Silvano Bianco / Banca: Marcos Antônio Kuva / Banca: Robinson Luiz de Campos Machado Pitelli / Banca: Roberto Estevão Bragion de Toledo / Resumo: O sorgo sacarino (Sorghum bicolor) é caracterizado por conter elevados teores de açúcares fermentescíveis em seu colmo, sendo considerado atualmente de alto potencial para compor a matriz energética nacional, ao produzir álcool durante a entressafra da cultura da cana-de-açúcar. A interferência das plantas daninhas é um dos fatores de maior importância durante a condução de uma lavoura. Uma vez que pouco tem sido estudado sobre esse tipo de sorgo, especificamente, estudos da interação entre as plantas daninhas e a cultura do sorgo sacarino são muito bem-vindas no desenvolvimento da agricultura energética. Os objetivos do trabalho foram: (I) determinar os períodos de interferência e índices fitossociológicos da comunidade infestante da cultura do sorgo sacarino; (II) analisar o desenvolvimento inicial de sorgo sacarino sob alta infestação de plantas daninhas; (III) estudar o efeito do exsudado do sorgo sacarino em outras espécies de plantas e avaliar o extrato radicular de uma potencial planta estimuladora da produção de sorgoleone pelo sorgo; (IV) avaliar o efeito supressor de restos culturais de sorgo sacarino sobre as plantas daninhas. Para o primeiro objetivo, os tratamentos consistiram de períodos crescentes da cultura em convivência e controle da comunidade infestante, em duas safras; sendo avaliada a biometria e a produção comercial do sorgo sacarino, além da determinação de índices fitossociológicos da comunidade infestante (densidade, dominância e importância relativa das espécies daninhas, além dos índices de diversidade e equitabilidade da comunidade). Em vasos, foi instalado o experimento para avaliar o terceiro objetivo, no qual híbridos de sorgo sacarino foram submetidos à presença de cinco plantas daninhas em alta densidade; sendo avaliadas as características morfofisiológicas do sorgo sacarino e a massa seca acumulada pela cultura e pelas plantas daninhas. Os estudos sobre a... / Abstract: Sweet sorghum (Sorghum bicolor) is featured by the high level of fermentable sugars present in its stalk. The crop is currently considered of high potential to compose the national energetic system, by producing alcohol during the sugarcane off season. The weed interference is one of the most important factors during a crop management. Because not too much have been studied about sweet sorghum, studies about the interaction between weeds and sweet sorghum crop are very welcome for the development of the bioenergy nationwide. The aim of this research were: (I) determine the periods of weed interference and the phytosociological indexes of the weed community on the sweet sorghum crop; (II) analyze the initial growth of sweet sorghum under high weed infestation; (III) study the effect of the sweet sorghum root exudate in other plant species and also evaluate the root extract of an potential stimulant plant on the production of sorgoleone by sorghum; (IV) evaluate the suppressive effect of sweet sorghum crop residues on weeds. For the first objective, the treatments were composed by increasing periods of weed presence and weed absence at two crop seasons; when it was evaluated the sweet sorghum biometry and yield, besides the determination of phytosociological indexes of the weed community (the relative indexes of density, dominance and importance, and the weed community indexes of diversity and equitability). In pots, it was carried out an assay in order to evaluate the third aim, in which hybrids of sweet sorghum were submitted to the presence of five weed species in higher density. It was evaluated the morphophysiological features of sweet sorghum and the dry mass of both crop and weeds. The studies about allelopathy were carried out in laboratory, using different methods of analytical chemistry. Bioassays was carried out in order to evaluate the activity of exudates of sweet sorghum hybrids on test plants seed germinability and seedling ... / Doutor

Orientador: Marcelo da Costa Ferreira / Coorientador: Rafael Gomes Viana / Banca: Rone Batista de Oliveira / Banca; Mariluce Pascoina Nepomuceno / Resumo: O espalhamento das gotas sobre superfícies vegetais pode indicar eficiência na aplicação de herbicidas. Porém, o espalhamento de uma gota depende das características da calda fitossanitária, especificamente das propriedades físico-químicas e as suas interações com as superfícies onde as gotas se depositam. As propriedades físicas, como tensão superficial e ângulo de contato podem ser alteradas pela adição de adjuvantes ao tanque do pulverizador. Assim, o desenvolvimento de pesquisas que avaliem a interação dos herbicidas associados a adjuvantes é importante para a recomendação correta do adjuvante, uma vez que o adjuvante pode proporcionar maior espalhamento da gota sobre a superfície de diferentes espécies de plantas, e potencializar o controle. Nesse sentido foram realizados dois estudos, sendo o primeiro para avaliar a tensão superficial e o ângulo de contato em três espécies do gênero Sida. No segundo foi avaliado o ângulo de contato de seis espécies de plantas daninhas e a relação do ângulo com o controle de Lantana camara e Crotalaria incana, de ocorrência em pastagem, ambiente vastamente cultivado no Brasil, mas no qual são raros os trabalhos desta natureza. Concluiu-se que a adição do adjuvante lecitina ao herbicida aminopiralide + fluroxipir reduz o ângulo de contato das gotas sobre as superfícies adaxial e abaxial de Sida cordifolia e Sida glaziovii. E quanto menor ângulo de contato maior controle das espécies avaliadas. / Abstract: The spreading of the drops on plant surfaces may indicate the possible success in herbicide application. However, the spread of a drop depends on the characteristics of the spray solution, specifically the physicochemical properties and their interactions with the surfaces where the drops settle. Physical properties such as surface tension and contact angle can be altered by the addition of adjuvants to the spray tank. Thus, the development of research that evaluates the interaction of herbicides associated with adjuvants is important for the correct recommendation of the adjuvant, since the adjuvant can provide greater spreading of the drop on the surface of different species of plants, and potentiate the control. In this sense two studies were carried out, being the first to evaluate the surface tension and the contact angle in three species of the Sida genus. In the second, was evaluated the contact angle of six weed species and the angle relationship with the control of Lantana camara and Crotalaria incana, a pasture, an area widely cultivated in Brazil, but in which works of this nature are rare. It was concluded that the addition of the lecithin adjuvant to the aminopyralid herbicide + fluroxypyr reduces the contact angle of the drops on the adaxial and abaxial surfaces of Sida cordifolia and Sida glaziovii. And the lower the contact angle the greater the control of the evaluated species. / Mestre