The effects of soil type, temperature, and moisture on the survival and seasonal germination of seeds of A. fatua and A. ludoviciana, buried at five depths in the soil, were studied in a glasshouse experiment. Seeds of both species germinated only when mean weekly minimum temperatures were below 20°C and mean weekly maxima below 28°. A. fatua germinated better than A. ludoviciana in the 20–30° range and was therefore the dominant species in autumn germinations of wild oats. Both species germinated throughout winter. Only 30% of the seeds sown produced seedlings. Of these 90% emerged in the first year after seeding and the remainder in the second year. Only 2% of the seeds sown remained viable after 18 months. The depth at which the seeds were buried, seed type, soil type. and moisture regime all affected the survival of seeds and the percentage that produced seedlings. An explanation is offered for the dominance of A. ludoviciana in the northern wheat-belt of eastern Australia.

Seeds of Avena ludoviciana after-ripened more rapidly with increasing temperatures up to 30°C and with increasing relative humidities between 16 and 100%. In continuous light, these seeds after-ripened more rapidly than in the dark. Seeds of different species and strains of wild oats after-ripened at different rates; primary seeds after-ripened more rapidly than secondary. One week after anthesis 60% of the viable primary seeds of A. ludoviciana were dormant, compared with 100% at maturity. The importance of these findings to studies on the physiology of dormancy and to the control of wild oats in the field is discussed.