Differential response to seed burial depth on seedling emergence of four Avena fatua L. populations in western Ibaraki, Japan

Summary Four populations of wild oats ( Avena fatua L.) collected from fields in western Ibaraki, Japan, were tested between 1999 and 2004 to determine the effect of seed burial depth on seedling emer gence. The persistence of seeds buried at a depth of 25 cm in the soil was also investigated. Plants were grown in the same field at NARO-ARC in Tsukuba, Ibaraki, Japan, and mature seeds were harvested. After 3 months in storage at room temperature, 100 seeds were buried in pots at 0, 5, 10, 15, and 20 cm depths with three replications for each depth. There were distinct differences in seedling emergence patterns between populations; most of the seeds in two populations emerged uniformly in the fall after the sowing year, whereas the third population emerged within a year. In the fourth population, there was a delay in the seedling emer gence pattern with the first flush occurring in early spring. The relationship between burial depth and emergence patterns differed between populations. In the three early-emerging populations, seeds buried at shallower depths emerged earlier, whereas in one late-emerging population, seeds buried at depths of 15 cm and 20 cm emerged earlier than those buried at 10 cm or less. For seeds buried at a depth of 25 cm, survival was associated with the emergence patterns. Most of the seeds in the early emergence population had germinated in the soil within 6 months, whereas more than 50% of the seeds in the late emergence population did not germinate. These results indicate that the emergence uniformity of wild oats is related to the depth of seed burial. Additionally, inter population variation in A. fatua germination requirements were found within a narrow regional scale in Japan.