Thesis (Ph. D.)--University of Western Australia, 2005. / Title from PDF title page (viewed on Nov. 9, 2006). Includes bibliographical references (p. 143-151).

Memoria para optar al título profesional de Ingeniera Agrónoma / La presente investigación tuvo por objetivo evaluar el efecto de dos alternancias de temperaturas en la germinación y emergencia de tres géneros de interés forrajero, simuladas en dos momentos de inicio del ciclo de crecimiento de la pradera anual de clima mediterráneo. Este estudio se llevó a cabo en el Laboratorio de Manejo de Praderas del Departamento de Producción Animal y el material de estudio fué recolectado en la Estación Experimental Germán Greve Silva ubicada en Rinconada de Maipú, ambos sitios pertenecientes a la Facultad de Ciencias Agronómicas de la Universidad de Chile. Para el ensayo de germinación, se trabajó con semillas de Bromus, Erodium y Vulpia, cosechadas en campo directamente desde las plantas, las cuales una vez en laboratorio, fueron sometidas a prueba de germinación y viabilidad. Los tratamientos fueron el resultado de la combinación de los tres géneros en estudio con las dos alternancias de temperaturas (16ºC/8ºC - temperaturas otoñales, 12ºC/4ºC - temperaturas invernales), obteniendo 6 tratamientos. Las semillas se dispusieron sobre papel filtro en placas petri, en cámara de crecimiento, con humedad constante y un fotoperiodo de 12 horas de luz y 12 horas de oscuridad. Las variables a medir fueron porcentaje de germinación y tasa de germinación por placa petri.

Italian ryegrass growth and production from positionally selective applications and sublethal rates of a nonselective herbicide were compared to growth and production when treated with diuron applied preemergence as a broadcast treatment and safened by activated carbon applied over the crop row. In the positionally selective treatments, herbicide spray was directed to leave an untreated zone over the crop row at planting. Growth analysis indicated no detectable differences when Italian ryegrass safened by directed spray was compared to Italian ryegrass safened by activated carbon. The major difference between systems was greater weed control in the crop row for carbon-safened treatments. The non-safened application superimposed sublethal diuron rates over Italian ryegrass and rattail fescue grown in varying densities and proportiors. Growth analysis of monoculture stands indicated differences due to planted density, species, and herbicide, whereas growth analysis of plants grown as space-planted individuals indicated difference due to species only. Diuron at the rates applied did not affect seed yield or above ground dry weight. Soil samples were taken in crop rows where diuron was applied as directed spray or broadcast spray safened by carbon. Samples were assayed and soil profile concentrations mapped. To assist future investigators' understanding of the role rainfall plays in herbicide movement from directed applications, elementary rainfall depth and occurrence models were examined. The Markov and mixed-exponential models adequately described rainfall occurrence and depth patterns for Corvallis, Oregon. / Graduation date: 1992

[Truncated abstract] Annual grasses have colonised a diverse range of environments in southern Australia. The “Silvergrasses” of the genus Vulpia are excellent examples being widely distributed, are prevalent weeds of agriculture and have had a long history to naturalise on the continent. Research was undertaken on Vulpia populations to identify if naturalising species have reproductive traits that provide propagules with the best chances of success. Furthermore, research aimed at investigating if these traits vary between species and their populations and how this variability related to the environment. A herbarium and field study was undertaken to establish what Vulpia species occur in SW Australia and to investigate environmental factors affecting their distribution. 169 herbaria specimens was examined and a botanical field survey of 189 sites was carried out in September 1998. Four species occur in the region: V. fasciculata, V. muralis, V. bromoides and two variants of V. myuros (V. myuros var. megalura and V. myuros var. myuros). V. bromoides and V. myuros were introduced early into the region while V. fasciculata and V. muralis more recently. It is plausible that Vulpia invaded the region via early seaport settlements and was spread by agricultural expansion. 96% of field sites contained V. myuros var. myuros, 79% V. myuros var. megalura, 50% V. bromoides, 6% V. fasciculata and 6% contained V. muralis. 90% of sites contained a mix of species and 9% of sites contained pure species stands. V. myuros var. myuros is the most widespread species and dominant form of V. myuros. It is found from high rainfall regions through to arid locations occurring on mostly light textured low fertility soils. V. muralis and V. fasciculata occur infrequently with the former widely dispersed and the later occurring predominantly on sands. V. bromoides occurs extensively in high rainfall regions but rarely extends to locations receiving less than 400-450mm annual rainfall and northward above 30°00’ latitude. It is predominantly on light to loamy textured soils that are fertile and acid. The most common species V. myuros and V. bromoides often coexist within sites but the dominance of one over the other is strongly correlated with growing season length and false break frequency. V. bromoides is positively correlated to growing season length and V. myuros is negatively related. The distribution of Vulpia species is strongly influenced by climate and soils. Variability in distribution is a reflection of the ecological differentiation between species to colonise different environments