Seed Longevity and Emergence of Volunteer Wheat in Upland Fields

Abstract

Since volunteer wheat normally sprouts from shed seeds, volunteer wheat control in farming should begin with ecological studies of these seeds. The objectives of this study were to clarify: 1) the forms of seeds shed during combine harvesting, and 2) the effects of these forms of seeds on wheat seed dormancy and longevity in the soil.
Wheat seeds shed during combine harvesting consist of both loose seeds and unthreshed ears (or ear seeds). The head feeding combine lost 98 seeds/m² and 121.7 seeds/m² of loose seeds and ear seeds, respectively, while, the conventional combine lost 18.2 seeds/m² and 42.4 seeds/m² (Fig. 2). This shows that many of seeds from the unthreshed ears fall in the field during combine harvesting.
The results of field experiments showed that the longevity of the seeds of wheat cultivars with a resistance to pre-harvest sprouting was greater than that of cultivars which showed a susceptibility to sprouting. The results also showed that the longevity of unthreshed ear seeds was longer than that of loose seeds in the soil (Table 2, Figs. 4 and 5).
Shed seeds of unthreshed ears during wheat harvesting are numerous, thus making the volunteer problem worse in subsequent barley cultivation.