Germination behaviour of red rice (Oryza sativa L.) seeds in field and laboratory conditions.

Two experiments were carried out in 1996-1998 to study (1) the germination behaviour of red rice seeds kept for different periods of time in field and laboratory conditions, and (2) the weed emergence behaviour in response to different burial depths. The first experiment was carried out considering mature red rice seeds of two biotypes which were exposed to field conditions and to 20 °C, for different periods of time, and then tested for their germinability over 6 months. The time required for red rice seed to germinate in petri dishes depended on the storage conditions and proved to be inversely related to the storage duration. Immediately after harvesting, the red rice seeds required 180 days of permanence in petri dishes to germinate. This time was reduced to 20 days when the seeds were exposed for 30 days at 20 °C or for 160 days in field conditions. The second experiment was conducted both in the greenhouse and in the field, placing seeds at different depths from 0 to 13 cm, in saturated and flooded soil conditions, and in loamy and clayey soil. The emergence was affected both by the depth of burial and the presence of a water layer on the soil sur- face, and occurred from a maximum depth of 10 cm. Most of the emergences were recorded in the 0-5 cm soil layer in saturated loamy soil (92-45%).