Effect of light environment during soil disturbance on germination and emergence pattern of weeds

This paper describes results from experiments which investigated the effects of light intensity during soil disturbance on germination and emergence pattern of weeds. Different emergence patterns were demonstrated for seeds which are instantly flash induced compared to seeds which are induced to germinate by integrating a weak light signal over a period of time. A reduced and delayed emergence is achieved after a disturbance in darkness compared to a soil disturbance in daylight. The increased emergence after soil disturbance in daylight is due to additional plants originating from seeds placed at a soil depth in the pots where daylight cannot penetrate and induce seeds to germinate, but which are induced during the short exposure period. A close relationship between soil disturbance intensity and number of weed plants emerging was found in field experiments with shallow harrowings. It was also shown that a portion of the increased number of seedlings arising when soil disturbance is carried out in daylight, compared to soil cultivation in darkness, originates from seeds germinating from deeper soil layers, resulting in a deeper average germination depth.