Wind dispersal of pollen from crops of oilseed rape ( Brassica napus L.)

Airborne oilseed rape pollen concentrations were measured within oilseed rape crops over five consecutive seasons 1985–1989. The seasonal pattern of pollen concentration was similar for each year but the onset of pollen production differed. Pollen concentration was diurnal with maximum concentrations generally occurring in the afternoon. Pollen concentration was slightly weather dependent with the largest concentrations found on days of high radiation and wind. Concentrations decreased with height above the crop showing that pollen grains were being lost from the crop. A mathematical model of pollen dispersal predicted that more than 60% of the pollen lost from a crop would still be airborne 100 m downwind of the crop, however, concentration at the ground would be between 2 and 10% of the value at the edge of the crop.