EFFECT OF LIGHT ENVIRONMENT DURING SOIL DISTURBANCE ON GERMINATION AND EMERGENCE PATTERN OF WEEDS

This paper describes results from experiments which investigated the e ffects of light intensity during soil disturbance on germination and e mergence pattern of weeds. Different emergence patterns were demonstra ted for seeds which are instantly flash induced compared to seeds whic h are induced to germinate by integrating a weak light signal over a p eriod of time. A reduced and delayed emergence is achieved after a dis turbance in darkness compared to a soil disturbance in daylight. The i ncreased emergence after soil disturbance in daylight is due to additi onal plants originating from seeds placed at a soil depth in the pots where daylight cannot penetrate and induce seeds to germinate, but whi ch 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 sh own that a portion of the increased number of seedlings arising when s oil disturbance is carried out in daylight, compared to soil cultivati on in darkness, originates from seeds germinating from deeper soil lay ers, resulting in a deeper average germination depth.