The inability to control wild oat (Avena fatua L.) in oat (Avena sativa L.) crops by chemical means limits growers to the use of cultural control methods. Delayed seeding is the most commonly used measure; however, both crop yield and quality may suffer as a result. The objectives of this research were to i) determine if western Canadian oat genotypes differ in competitive ability, ii) determine the effect of increased plant populations on oat wild oat competition, iii) determine the effect of wild oat competition on oat quality, and iv) establish whether or not oat genotype and seed size affect germination characteristics under low temperature and moisture stress. These objectives were tested using field and laboratory experiments. Morphologically diverse oat genotypes differed in their ability to both tolerate wild oat competition and interfere with wild oat growth. Although low yielding under weed-free conditions, when subject to wild oat competition CDC Bell was able to maintain yield, reduce wild oat seed production and was the most competitive of the genotypes examined. Increased plant populations achieved through higher seeding rates provide an effective means by which to enhance the competitive ability of oat genotypes resulting in reduced yield loss and wild oat seed production. With the exception of the percentage of wild oat seed in harvested oat samples, wild oat competition had minimal effect on oat quality. Differences in germination characteristics were observed among the genotypes examined. Conclusions that emerge from this research are that i) oat genotypes differ in their ability to tolerate and interfere with wild oat competition, ii) increased plant populations may provide a long-term control measure that may reduce weed seed contribution to the soil seedbank as well as enhance the competitive ability of oat, iii) wild oat competition has minimal effect on milling oat quality with the exception of percentage of wild oat seed in harvested samples and iv) that median germination time varies among oat genotypes.

The inability to control wild oat (Avena fatua L.) in oat (Avena sativa L.) crops by chemical means limits growers to the use of cultural control methods. Delayed seeding is the most commonly used measure; however, both crop yield and quality may suffer as a result. The objectives of this research were to i) determine if western Canadian oat genotypes differ in competitive ability, ii) determine the effect of increased plant populations on oat wild oat competition, iii) determine the effect of wild oat competition on oat quality, and iv) establish whether or not oat genotype and seed size affect germination characteristics under low temperature and moisture stress. These objectives were tested using field and laboratory experiments. Morphologically diverse oat genotypes differed in their ability to both tolerate wild oat competition and interfere with wild oat growth. Although low yielding under weed-free conditions, when subject to wild oat competition CDC Bell was able to maintain yield, reduce wild oat seed production and was the most competitive of the genotypes examined. Increased plant populations achieved through higher seeding rates provide an effective means by which to enhance the competitive ability of oat genotypes resulting in reduced yield loss and wild oat seed production. With the exception of the percentage of wild oat seed in harvested oat samples, wild oat competition had minimal effect on oat quality. Differences in germination characteristics were observed among the genotypes examined. Conclusions that emerge from this research are that i) oat genotypes differ in their ability to tolerate and interfere with wild oat competition, ii) increased plant populations may provide a long-term control measure that may reduce weed seed contribution to the soil seedbank as well as enhance the competitive ability of oat, iii) wild oat competition has minimal effect on milling oat quality with the exception of percentage of wild oat seed in harvested samples and iv) that median germination time varies among oat genotypes.

Algunas especies vegetales se consideran malezas debido a que alcanzan niveles poblacionales tales, que al competir con los cultivos causan perjuicios sobre su producción. Por este motivo, en determinadas ocasiones es necesario realizar operaciones de control sobre las poblaciones de malezas para reducir su infestación hasta valores que permitan obtener niveles de producción deseados. A nivel mundial el control químico ha sido el método más práctico y eficiente para controlar malezas, especialmente en cultivos extensivos. Sin embargo, el uso continuo de herbicidas desde hace más de 40 años trajo aparejado un impacto negativo sobre el medio ambiente, la salud y la proliferación de malezas resistentes. Estas consecuencias se deben tener en cuenta para definir manejos adecuados a largo plazo. Desde una perspectiva estratégica, un programa sostenible de manejo de malezas debería basarse en una combinación de métodos tanto preventivos como curativos que apliquen principios basados en el conocimiento, dando lugar a lo que se conoce como Manejo Integrado de Malezas, MIM. En este contexto, el modelado matemático se presenta como una herramienta apropiada para ayudar a guiar el proceso de toma de decisiones asociado al MIM. En esta tesis se propone un modelo de simulación para asistir en la toma de decisiones relacionadas con el MIM. El modelo se desarrolló en colaboración con profesionales extensionistas y fue concebido como una herramienta flexible y adaptable a diversos sistemas de producción agrícola, poseyendo un mayor nivel de detalle que otros modelos similares. Dicho modelo permite simular la dinámica multianual de una maleza en competencia con el cultivo. El ciclo de vida de la maleza se representa a través de los componentes demográficos típicos (ej. banco de semillas, plántulas, adultos en estado vegetativo y reproductivo, producción de semillas). El desarrollo del cultivo se simula de forma simplificada a fin de cuantificar diariamente los efectos de la competencia interespecífica. La simulación de distintas estrategias de MIM permite calcular y comparar indicadores económicos, ambientales y agronómicos. Palabras claves: Manejo Integrado de Malezas, Modelado de sistemas agrícolas, Avena fatua L., Euphorbia davidii Subils., Trigo, Cebada, Soja, Competencia de malezas, Asistencia a la toma de decisiones, Margen bruto, Valor actual, Impacto ambiental, Malezas resistentes, Dinámica poblacional de malezas. / Some species considered weeds reach population levels that impact on crops’ production. For this reason, on certain occasions, it is necessary to carry out control operations to reduce weed infestations to levels compatible with reasonable crops’ yields. Worldwide, chemical control has been the most practical and efficient method for controlling weeds, especially in extensive crops. However, the continuous use of herbicides for over 40 years generated a well-known negative impact on environment and health and the proliferation of resistant species. These environmental consequences must be taken into account to define appropriate long-term management practices. From a strategic perspective, a sustainable weed management program should be based on a combination of preventive and curative methods that apply knowledge-based principles, leading to as the so-called Integrated Weed Management (IWM). In this context, mathematical modelling arises as an appropriate tool to assist in the decision- making process associated with IWM. This thesis proposes a simulation model to support decision-making related to IWM. The model was developed in collaboration with extensionists and was conceived as a flexible and adaptable tool for various agricultural production systems, possessing a higher level of detail than similar models. This model simulates multi-year dynamics of a weed in competition with a crop. The weed's life cycle is represented through typical demographic components (e.g. seed bank, seedlings, vegetative and reproductive individuals, and seed production). The development of the crop is simulated in a simplified manner in order to quantify the daily effects of interspecific competition. The simulation of different IWM strategies allows for the quantification and comparison of economic, environmental, and agronomic indexes.