DISPERSAL OF BROMUS-STERILIS AND ANTHRISCUS-SYLVESTRIS SEED WITHIN ARABLE FIELD MARGINS

The majority of Bromus sterilis (99%) and Anthriscus sylvestris (87%) seed marked in a field margin, and B. sterilis marked in an open field (84.5%) were disseminated within 1 m of the source. The remaining see ds were observed up to 2 m, 3 m and 3.5 m from the source, respectivel y. Boundary treatment, sprayed or non-sprayed, had no significant effe ct on the proportion of recovered seed. Wind speed and direction were recorded in the field margin and open field on two sites, and wind spe ed was generally halved on the leeside of the hedge. Marking seeds wit h aerosol dye did not affect the rate of seed loss from the seed traps ; although more seeds were lost from traps in the sprayed boundary str ip (28%) than the non-sprayed strip (16%). A preliminary investigation of B. sterilis seed dispersal by a combine harvester, recovered 46% o f seeds +/-1 m from the source, with the remaining seeds up to 7 m beh ind and 53 m in front, Thirty-one percent of marked seeds were recover ed from the combine swath.