Avena fatua development and seed shatter as related to thermal time

Avena fatua seeds remaining on the plant at harvest and taken into the comb ine harvester may be dispersed over large areas. The objective of this stud y was to characterize the development of A. fatua in comparison to spring T riticum aestivum. As part of this objective, the rate of seed shed in A. fa tua relative to development of T. aestivum was determined. Avena fatua and T. aestivum had similar phyllochron intervals within locations but differed between locations. Plant development as measured by the Zadoks plant devel opment scale was consistent within plant species between locations. Seed sh ed in A. fatua was also consistent between locations. Most of the seed shed occurred within 2 wk, and the cumulative seed shed followed a sigmoidal pa ttern. The seed shed occurred as T. aestivum was ripening, and the percenta ge of seed shed appears to be related to the water content of the T. aestiv um spike. Because of this relationship, the proportion of seed remaining on A. fatua at harvest could be managed by changing the timing of crop harves t.