Seed dispersal by forage harvester and rigid-tine cultivator in maize

Harvest and tillage operations are a major factor in seed dispersal in agricultural crops. We studied the effect of harvesting and cultivation on seed dispersal in continuous maize. A suite of cultivated plant species were used as model weed species to avoid potential sampling problems. Dispersal on the entire field was assessed by counting emerged seedlings in contiguous quadrats. Species that had seeds on the plant at the time of harvest were spread further in the direction of traffic by harvest and cultivation combined than species whose seeds had been placed on the soil surface, as judged by the 50th, 90th and 95th percentiles of the cumulative dispersal distribution. Harvesting alone did not cause this effect. The use of a cultivator after harvesting significantly increased the distance travelled in the driving direction for three species with ripe seeds during harvest. Dispersal distributions resulting from cultivator operations showed long tails, extending over the whole of the sampled area, and they were quite variable. The headlands accumulated plant debris that had been collected and dragged over the field by the cultivator. This study shows how weed biology and its interaction with machinery can facilitate dispersal of plants at the field scale.