In the fall of 2011, a study was initiated at the Western Kentucky University Farm in Bowling Green, Kentucky on a Crider silt loam (Typic Paleudalf). The objective of this study was to determine cultivar, mowing height, and herbicide effects on bermudagrass, Cynodon dactylon [L.] Pers., suppression in tall fescue, Schedonorus arundinaceus [Schreb.] Dumort., nom. cons. The experimental design was a split plot design with whole plots consisting of varying mowing heights and split plots consisting of different herbicide treatments with three replications. Two separate experiments were conducted. The tall fescue variety ‘KY 31’ was utilized for one study and the turf type cultivar ‘Bullseye’ was utilized in the other. In the fall of 2011, glyphosate (Roundup Pro) was applied to selected plots at the rate of 0.36 kg ae/ha. ‘KY 31’ and ‘Bullseye’ tall fescues were sown into an existing mixed stand of common and hybrid bermudagrass at 342 kg pls/ha. Mowing heights were maintained at 7.62 cm, 10.16 cm, and 12.70 cm. In the spring of 2012, treatments containing fenoxaprop (Acclaim Extra), mesotrione (Tenacity), and fluazifop (Fusilade II) were applied to selected plots at the rates of 0.07 kg ai/ha, 0.48 kg ai/ha, and 0.24 kg ai/ha respectively. A non-ionic surfactant at 0.25% (v/v) was utilized in treatments containing mesotrione and fluazifop. Three weeks later these treatments were applied a second time. Data were collected visually on turf quality, tall fescue cover, broadleaf weed cover, and bermudagrass cover. The study was repeated in 2012 – 2013. Fluazifop and glyphosate + fluazifop resulted in significantly lower turf quality than all other treatments up until ten weeks after initial treatment. Treatments containing fluazifop significantly reduced tall fescue cover but also significantly suppressed bermudagrass cover the greatest. However, these treatments also resulted in the greatest amount of broadleaf weed cover. High mowing heights may play a role in achieving high turf quality ratings and better broadleaf weed and bermudagrass suppression in forage type tall fescue than in turf type tall fescue.

La Electroforesis Capilar en Fase Micelar (MECC) es una nueva técnica de separación desarrollada a partir de la Electroforesis Capilar en Zona (CZE) y basada en principios tanto cromatográficos como electroforéticos, capaz de separar compuestos aniónicos y neutros conjuntamente: mientras que para los compuestos neutros el fundamento de la separación es similar al de la cromatografía líquida, para los compuestos aniónicos la separación está basada principalmente en sus diferentes movilidades electroforéticas.La presente tesis doctoral se ha planteado con el objetivo principal de profundizar en esta técnica analítica y estudiar su aplicación en la determinación de compuestos de interés medioambiental, concretamente herbicidas de las familias de los fenoxiácidos y las fenilureas y productos derivados de su degradación. Para ello se ha dividido la memoria en 5 capítulos:En el capítulo 1º se realiza una introducción de la técnica CZE, estudiándose fundamentos teóricos de separación y detección y su instrumentación. Finalmente se realiza un pequeño estudio experimental de separación de varios herbicidas fenoxiácidos. Con ello se obtiene una base teórica y experimental sobre la Electroforesis Capilar necesaria para el capítulo 2º, en el cual se profundiza en el análisis mediante MECC. En este capítulo se estudian las bases teóricas de esta técnica y se aplica en la resolución de una mezcla de herbicidas fenoxiácidos y fenilureicos. El estudio de la técnica MECC se completa en el capítulo 3º, donde se optimiza la separación de la mezcla de los herbicidas adicionando a la disolución de trabajo diferentes alcoholes alifáticos. Se discuten las variaciones experimentales observadas y se desarrolla un modelo teórico que explica estas variaciones. En este modelo entran en juego factores como las características fisico-químicas de las micelas y sus variaciones cuando están en contacto con alcoholes lineales.En el capítulo 4º intentamos superar una de las mayores limitaciones de la Electroforesis Capilar que es la falta de sensibilidad. Para ello se desarrollan sistemas de pre-concentración de la muestra on-line, basados en la inyección de grandes volúmenes de muestra y la posterior eliminación de parte la matriz que contiene esta muestra, y sistemas de pre-concentración off-line mediante columnas de extracción en fase sólida de carbono grafitizado. Con estos dos procedimientos de concentración se consigue llegar a las sensibilidades necesarias para utilizar el sistema MECC en el análisis de pesticidas de muestras medioambientales.Toda la información obtenida en los capítulos anteriores es aplicada en el capítulo 5º en un estudio de degradación de varios herbicidas fenoxiácidos y fenilureicos. Para ello se tuvo en cuenta diversas vías de degradación como son la fotodegradación o la hidrólisis, y diferentes condiciones ambientales. Con este estudio se consiguieron datos relevantes en la comprensión de los mecanismos de degradación de los herbicidas estudiados: cinéticas de reacción y constantes de velocidad de degradación, productos de derivados de la fotodegradación y la hidrólisis, etc. / Micellar Electrokinetic Capillary Chromatography (MECC) is a new separation technique developed from Capillary Zone Electrophoresis (CZE) and based on chromatographic and electrophoretic principles. It is able to separate anionic and neutral compounds simultaneously. The separation of neutral compounds by MECC is similar to that by Liquid Chromatography. For anionic compounds, the separation is largely based on its different electrophoretic mobilities. The main objective of this doctoral thesis is to study this analytical technique and its application in the determination of compounds of environmental interest, concretely, phenylurea and phenoxyalkyl acid herbicides and products derived of their degradation. The thesis has been divided in 5 chapters: In the 1st chapter, it is carried out an introduction of CZE procedure, being considered theoretical principles of separation and detection and their instrumentation. It finishes by performing a brief experimental study of separation of several phenoxyalkyl acid herbicides. We obtain a theoretical and experimental basis about Capillary Zone Electrophoresis required in 2nd chapter, in which we examine the analytical technique MECC. In this chapter, the theoretical principles of this technique are developed and applied in the resolution of a mixture of phenylurea and phenoxyalkyl acid herbicides. The study of MECC is completed in 3rd chapter, where the separation of the mixture of herbicides is optimised adding aliphatic alcohols. The observed experimental variations are discussed and explained by a theoretical model. In this model, it is explained factors like the physico-chemical characteristics of the micelles and their variations when they are in contact with aliphatic alcohols. In the 3rd chapter, we try to overcome one of the biggest limitations in the Capillary Electrophoresis: the sensibility. We develop on-column sample pre-concentration systems, based on the injection of a very large volume of sample and the elimination of the sample matrix. We also expose off-column sample pre-concentration systems by means of solid phase extraction cartridge of graphitized carbon black. With these concentration procedures, it was possible to achieve the necessary sensibilities to use MECC system in environmental analysis. All the information obtained in previous chapters is applied in 5th chapter in a degradation study of several phenylurea and phenoxyalkyl acid herbicides. We kept in mind various degradation processes like photodegradation or hydrolysis and different environmental conditions. We reach interesting data to the understanding of degradation mechanisms of the determined herbicides: kinetic of reaction and degradation constants, products derived of photodegradation and hydrolysis, et cetera.

No description available.

Organophosphate hydrolase (OPH, EC 3.1.8.1) is a bacterial enzyme with a broad spectrum of potential substrates that include organophosphorus pesticides, herbicides, and chemical warfare agents. OPH has been expressed successfully in bacterial, fungal, and insect cell culture systems; however, none of these systems produces amounts of enzyme suitable for applications outside of the research laboratory. Therefore, a transgenic Zea mays L. (maize) system was developed to express OPH as an alternate to the current OPH expression systems. The bacterial gene encoding the OPH protein was optimized for transcriptional and translational expression in maize. The optimized gene was inserted into the maize genome under the control of embryo specific, endosperm specific, and constitutive plant promoters. Select transformants were analyzed for the expression of OPH. Expression was observed in the seeds of plants transformed with each of the three constructs with the highest expression observed with the embryo specific and constitutive promoter constructs. The highest OPH expressing lines of transgenic maize had expression levels higher than those reported for the E. coli expression system. OPH was purified from transgenic maize seed and analyzed for posttranslational modification and kinetic properties. OPH was observed to undergo a glycosylation event when expressed in maize that yielded at least two forms of OPH homogolous dimer. The glycosylated form of OPH bound tightly to the Concanavalin A sepharose and remained active after months of storage at room temperature. OPH activity was checked against a number of organophosphate herbicides. Enzymatic activity was observed against the herbicide Amiprophos-methyl and kinetic properties were measured. Enzymatic activity was also tested against the organophosphate Haloxon. Transgenic maize callus, leaf, and seed tissue could be screened for the presence of the optimized opd gene by enzymatic activity. Comparison of the growth of transgenic and control callus on media containing organophosphates showed that the transgenic callus was resistant to the herbicidal effects of haloxon. Transgenic plants expressing OPH were also resistant to the herbicide bensulide when compared to control plants. This indicates that OPH can be used as a screenable marker in plant systems and may be a potential scorable marker system as well.

Thesis (Ph.D.)--Mississippi State University. Department of Plant and Soil Sciences. / Title from title screen. Includes bibliographical references.

Thesis (Ph. D.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains xii, 243 p. : ill. Vita. Includes abstract. Includes bibliographical references (p. 213-240).

A significant acreage of poorly drained sites occurs in the Western Gulf region of the United States. These sites experience standing water through much of the winter and spring, resulting in poor seedling survival. In addition, the sites occasionally experience a summer drought that affects tree growth. This study was designed to determine the effects of intensive forest management on seedling growth and physiology, and to enhance seedling performance under these harsh conditions. Fertilization, chemical vegetation control and mechanical site preparation were used in different combinations to test the effects of these intensive forest management tools on seedling above- and below-ground growth, survival, water status, gas exchange attributes, and nutrient concentrations in the foliage and soil solution. Ten sites were established in southern Arkansas in 1998 and 1999 to monitor loblolly pine (Pinus taeda L.) seedling performance in three consecutive growing seasons between 1998 and 2000. Fertilization, chemical vegetation control and mechanical site preparation increased above-ground growth. Growth increment from mechanical site preparation was comparable to that from fertilization. Survival was not affected by any treatment. Fertilization enhanced root growth, more so in the shallow soil layers. Subsoil bulk density greatly restricted root growth, resulting in decreased above-ground growth. Chemical vegetation control made more soil water available to the seedlings during drought, resulting in increased seedling water potential. The effect of chemical vegetation control on seedling water potential was absent in the early growing season when soil moisture was abundant. Seedlings on plots treated with bedding-plus-fertilizer or bedding alone experienced stomatal closure at times of severe water stress while those treated with chemical vegetation control were able to continue net carbon dioxide assimilation. Fertilization did not increase needle nutrient concentrations, but increased needle weight, thereby increasing total nutrient content. Fertilization increased base cation concentrations in the soil solution, but had no effect on nitrogen and phosphorus concentrations. Intensive forest management was found to be a viable tool for optimum loblolly pine seedling growth and survival on poorly drained sites in the Western Gulf region of the United States.

Increased amounts of pesticide production and application of pesticides for agriculture, plant protection and animal health has resulted in soil, water and air pollution, consequently relating a serious risk to the environment and also to human health. Pesticides include several groups of compounds, herbicides, insecticides, rodenticides and fumigants consisting of several hundred individual chemicals. Herbicides are an integral pan of modem agriculture and for industries requiring total vegetation control. Most herbicides are soil applied and more and more concern is raised that herbicides not only affect target organisms but also the microbial community present in soil. The ESKOM sub-station Zeus, in Mpumalanga (South Africa) used to apply an industrial weed control program for the eradication of vegetation, which led to the contamination of soil by several herbicides. These herbicides consisted of Bromacil, Tebuthiuron and Ethidimuron which are all photosynthesis inhibitors, more specifically, they disrupt the plastoquinone protein during electron transport at photosystem I1 (PSII). In this study the effect of biostimulation and bio-augmentation of a specific bioremediation agent (B350) as prescribed by ESKOM, on residual herbicides, Bromacil, Tebuthiuron and Ethidimuron was evaluated by monitoring the soil physical and chemical properties, microbial attributes, including potential microbial activity and community structure, as well as the physiological effect experienced by plants (Cynodoh dactylon and Zea mays). Results from soil physical and chemical analyses were correlated with results obtained for the functional and structural diversity of microbial communities. All results were investigated through statistical and multivariate analysis and the most prominent soil physical and chemical parameters that influence the biological and biochemical properties of the soil were identified. Results obtained from this study indicated that there were no significant difference (p < 0.05) between the treatments, with bioremediation agent, irradiated agent and without the agent based on results obtained from soil microbial properties and plant physiology. Before the trial started the uncontaminated soil showed an active microbial function, characterised by dehydrogenase, urease and arylsulphatase activity, but community structure was not very diverse. The contaminated soil, irradiated contaminated soil and silica sand showed less enzymatic function and was characterised by phospholipid fatty acid groups, mid-branched saturated fatty acids, terminally branched saturated fatty acids, normal saturated fatty acids and monosaturated fatty acids which are indicative of microorganisms that survive better in harsh environments. Three weeks after the addition of the specific bioremediation took place, the uncontaminated soil showed an increase in P-glucosidase activity and percentage organic carbon (%C), which could be a result of the presence of available plant material. Furthermore, an increase in major PLFA groups were seen, suggesting that an increase in diversity within the soil community occurred. The contaminated soil, irradiated contaminated soil and silica sand once again was characterised by a low microbial function and diversity, showing no improvement. Fluorescence data clearly show a decline in PS 11 function that result in the decline of the rate of photosynthesis, which was seen from COz gas exchange rates. Furthermore, the decrease in photosynthetic activity after three weeks was too severe to supply additional information about the mechanism within photosynthesis or the photoprotective mechanisms. A detailed study was conducted in which a 3: 1 dilution of contaminated soil with silica sand, was also monitored for changes within plant physiology. Results revealed that inhibition of PS I1 function already takes place within a few days time and the decline in photosynthesis is as a result of electron transport that does not supply adenosine triphosphate (ATP) and P-nicotinamide adenine dinucleotide (NADPH) to the Calvin cycle (or Reductive Pentose Phosphate pathway). It does not appear that rubulose-1,sbisphosphate carboxylase-oxygenase (Rubisco) is affected within the Calvin cycle. As a result of PS I1 function failure, reaction centres are damaged by the production of harmful singlet oxygen and photoprotective mechanisms (xanthophyll cycle) can not be activated. Thus, except for dealing with ineffective electron transport, additional damage is caused to physiological functions. After six weeks a decrease in the estimated viable biomass for all growth mediums was found. Results of the of trans- to cis- monoenoic fatty acids and cyclopropyl fatty acids to their monoenoic precursors ratios indicated that the soil microbial community for the contaminated growth mediums, all experienced nutritional stress throughout this trail. The specific bioremediation agent (B350) used, seemed to have no effect on the microbial function and community structure within soil and as agent had no effect on the residual herbicides or the plant physiology which experienced an extreme decline in major metabolic functions. / Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2

Selective application of herbicide in agricultural cropping systems provides both economic and environmental benefits. Implementation of this technology requires knowledge of the location and density of weed species within a crop. In this study, two image classification techniques (Artificial Neural Networks (ANNs) and Maximum Likelihood Classification (MLC)) are compared for accuracy in weed/crop species discrimination. In the summer of 2005, high spatial resolution (1.25mm) ground-based hyperspectral image data were acquired over field plots of three crop species seeded with two weed species. Image data were segmented using a threshold technique to identify vegetation for classification. The ANNs consistently outperformed MLC in single-date and multitemporal classification accuracy. With advancements in imaging technology and computer processing speed, these network models would constitute an option for real-time detection and mapping of weeds for the implementation of site-specific herbicide management. / xii, 106 leaves : ill. (col. ill.) ; 29 cm

The primary objective of this research project is to develop a system for precision spraying of herbicides in a corn field. Ultimately, such a system would permit real-time image collection, processing, weed identification, mapping of weed density and sprayer control using a tractor-mounted digital camera and on-board computer. The initial hypotheses underlying this project were (1) that it is possible to train an artificial neural network (ANN) to distinguish weeds from a crop species (corn in this study); (2) that it is possible to differentiate between weed species; and (3) that precision spraying can significantly reduce the quantity of herbicide needed to protect crop yields, thus reducing both the costs and environmental impacts of such applications. Thus, development of an ANN for this purpose was the main focus of the research project. / Since the success of ANN development is primarily dependent on the type of information that it is provided, much of the work involved investigation of different approaches to extracting information from the digital images of field sections and individual objects (weeds or corn plants), as well as analysis of the type of information extracted. The applicability of a given image processing method was evaluated in terms of the image recognition accuracy, as well as the computer time and memory requirements for processing and obtaining ANN output, since speed is of the essence in real-time applications. The greenness method based on a pixel-by-pixel analysis of red-green-blue intensity value of the original images was the most successful and was used in further work. / As it turned out, ANN development for this purpose was difficult. While the success rate for recognition of corn plants was high (80% or greater), the success rate for recognition of weeds tended to be low. Improvements in weed recognition were met with decreases in the success rate of corn recognition. Differentiation between weed species was less than desirable. Differentiation between corn and a given weed species was also not as good, particularly when the weed species was similar in appearance to the young corn plant. / Therefore, another strategy was developed to recognize weeds in the field by taking images between the corn rows. Previously, the images were taken randomly in the field. The images were processed to obtain percent greenness in each image and this information was used to create weed coverage and weed patchiness maps. Based on these maps, herbicide spraying was decided and spraying amounts were determined. In terms of real-time, it was possible to process the equivalent of one metre of row per second. Although this is slow compared to tractor speed in the field, the computer was not operating under dedicated conditions as one would require for the real-time application. Thus, the results were considered encouraging. / The final stage of the work involved an evaluation of the potential herbicide savings from a precision spraying system. This was done by using the weed coverage and weed patchiness maps as inputs to a simulated fuzzy logic controller, and integrating the output of the controller over the field area corresponding to the input images. The simulations with different fuzzy rules and membership functions indicated that the precision spraying approach could reduce the amount of herbicide needed for weed control in a corn field by up to 15%.