Seed dormancy and seedling emergence studies in Avena fatua L.

Studies were made of seedling emergence of three phenotypes of Avena fatua L. with different coloured lemmas (fA, fB, fC) originally collected from one site. Each phenotype was grown under the same conditions in 1975 and the resulting seed buried 25 mm deep in soil immediately after collection. The soil was either left uncultivated (all phenotypes) or cultivated monthly (phenotype fA only). Seedling emergence was assessed weekly and the number of remaining viable seeds was determined at the end of three years. Seeds of different lines of A. fatua (fA phenotypes) obtained from separate locations were grown under the same conditions in 1983, buried and seedling emergence monitored for 8.5 months. Without cultivation, overall emergence (mean of three phenotypes) in successive autumns and springs was 9 %, 18 %, 9 %, 33 %, < 1 %, 14 % and < 1 %. A further 3 % of viable seeds were recovered at the end of the experiment. Periodicity of emergence was the same for all phenotypes. Actual numbers of seedlings emerging in each of the periods varied between phenotypes. Total emergence of seed from the inner zone of panicles was significantly less than that from the outer zone, although there was little difference between the two zones in each of the natural emergence periods. Cultivation increased emergence, particularly from secondary seed in the first spring after burial, but did not changes its periodicity. By the second spring seed numbers had declined, and seedling counts were similar from cultivated and non-cultivated soil. No viable seed remained in the cultivated soil after three years. Emergence from the two lines of fA was very different. Seedling emergence occurred after hot dry conditions, or in warm periods immediately after periods of chilling, particularly those below 4-degrees-C.