THE EFFECT OF DEPTH OF BURYING AND FREQUENCY OF CULTIVATION ON SURVIVAL AND GERMINATION OF SEEDS OF WILD OATS ( AVENA FATUA L. AND AVENA LUDOVICIANA DUR.)

Summary. Seeds of Avena fatua and A. ludoviciana were sown at a depth of 15 cm or mixed into the top 5 cm of soil in small field‐plots at Rothamsted and subjected to 5 different regimes of depth and frequency of cultivation for 3 years, after which all plots were dug to 15 cm in spring and autumn for a further 4 years. Seedlings were counted and no plants were allowed to produce seeds. After 7 years, soil‐samples showed that very few intact seeds of A. fatua and none of A. ludoviciana remained, although less than 20% of the seeds sown had produced seedlings. Laboratory tests after 4 to 8 years’dry slorage showed seeds of both species to be viable. The maximum survival of viable seeds, estimated by seedling‐emergence, was 61 months for A. fatua and 33 months for A. Indoviciana . Seeds of A. fatua survived slightly longer at 15 cm than in the top 5 cm of soil. Survival of A. ludoviciana was less affected by depth and cultivation, except that birds ate some shallow‐sown spikelets in the first fortnight after sowing. A. fatua germinated in spring and autumn, and A. tudoviciana in winter, irrespective of age of seed and cultivation of soil. Frozen soil delayed emergence of A. ludoviciana seedlings lor varying periods between December and March. Seedlings of A. ludoviciana were slightly more winter‐hardy than A. fatua . More seedlings of A. fatua appeared in the second spring than at any other time, but 80% of the seedlings of A. ludoviciana appeared in the first autumn and winter. Effets de la profondeur d'enfouissement des graines et de la fréquence des façons culturalles sur la longévité et la germination des semences de Folle‐Avoine (Avena fatua L. et A. ludoviciana Dur .)