The study of the effects of cropping systems on buried weed seed is very costly. Most of the experiments of this nature were conducted prior to the introduction of herbicides. New techniques, material and methods are needed and could result in more research in this area of study. A polyester material was experimented with which provided a means for mechanically washing buried weed seed packets. This was accomplished through the development of an experimental seed packet washer. The washer and the polyester material made it possible to wash the soil from delicate seedlings growing inside the packets without damage to them. They in turn could be examined without removal from the seed packets making the procedure many times more economical. A seed removal technique was also developed which worked well in separating weed seed from mineral soil samples. This was accomplished by making slight modifications in the experimental seed packet washer regarding screening,.slope, water volume and the usage of various sizes of soil sieves. An economical bioassay method for studying the effects of crop leachates on red sorrel and rice germination and growth was also developed while simultaneously testing cropping system effects on buried weed seed in the greenhouse and field. This method and technique holds promise for other types of plant experiments involving liquid and culture media. Thirty-seven monoculture cropping systems were tested in the greenhouse and fourteen in the field for their effects on nine different buried weed seed species. Evidence is provided to show that broccoli, beans, asparagus, quackgrass, tomatoes and other plants fray be inhibitory to the subsequent germination and viability of the buried seed of Rumex acetosella L., Rumex crispus L., Brassica campestris L. and Amaranthus retroflexus L. / Graduation date: 1975

Weed seeds contaminating cattle feed can pass unaffected through the animal's digestive tract and may germinate when manure is returned to land as fertilizer. This investigation was undertaken to determine the effects of anaerobic fermentation of raw manure on the viability of Johnsongrass and Fall Panicum seeds which may be present in the waste. Dairy waste containing Johnsongrass and Fall Panicum seeds were subjected to batch and continuously-fed anaerobic fermentation processes in laboratory-scale digesters. The effect of influent solids concentration (4% and 6%) and retention time (15 days and 20 days) on seed viability was observed. The experiments were carried out in the mesophilic temperature range [35°C±1ºC]. Fall Panicum seeds were found to be less resistant to anaerobic digestion than Johnsongrass seeds. Greater seed destruction was achieved in 20-day digesters than in the 15-day digesters. The influent solids concentrations did not have significant effect on seed viability. By applying the Schafer-Chilcote seed population model, it was observed that the fermentation process was more effective in destroying non-dormant seeds than dormant seeds. / Master of Science

[Truncated abstract] In the crop growing areas of Western Australia, two economically important weed species, Lolium rigidum Gaud. (annual ryegrass) and Raphanus raphanistrum L. (wild radish), have evolved widespread herbicide resistance to multiple chemistry groups. Consequently, grain growers in the region have adopted an integrated approach to weed management that includes many non herbicide tools, however many more are needed as these weed species become increasingly more difficult to control. This thesis examines, in a series of field trials carried out in the Western Australian crop growing area, the potential for weed seed predation of annual ryegrass and wild radish by naturally occurring granivores as a new weed management tool for grain growers . . . The study discusses the implications of these results with the view to manipulating predation of weed seed through agricultural management practices. Ants were shown to be the dominant seed predator in this environment, especially in the centre of fields. The study has identified that the ant species Melophorus turneri (Forel), Monomorium rothsteini (Forel), Pheidole hartmeyeri (Forel) and Rhytidoponera metallica (Smith) are potential biological control agents for annual ryegrass seeds while P. hartmeyeri was identified as the only species suitable for biological control of wild radish seed pods. Ants were found to be sensitive to disturbance and some to crop residue type and these effects are discussed in relation to seed removal. This study of weed seed predation in agricultural fields is the most complete in this environment and can be used to inform further work in this area. It has identified that naturally occurring granivores can be used as a weed management tool.