Rigid brome is a problematic weed of southern Australian cropping systems. Increased knowledge about the ecology of rigid brome and the influence of management strategies on its seedbank dynamics could facilitate development of more effective weed control programs. A field study was undertaken to investigate seedbank persistence and the influence of different management strategies on rigid brome control at Lock in South Australia during 2003 to 2005. Seeds of rigid brome were found to persist in the soil for up to 3 yr, with > 20% of the seedbank persisting from one season to the next. Therefore, a single year management program against this weed species is likely to be ineffective and could result in rapid buildup in weed infestations. However, management strategies that combined effective herbicides (Clearfield^TM technology) and crop competition over consecutive years provided effective control of this troublesome weed. Such cropping systems reduced rigid brome density (1 to 10 plants m⁻²) and seed production (8 to 160 seeds m⁻²) in the final crop of the 3-yr cropping sequence as compared to common grower practice of trifluralin and triasulfuron mixtures (138 plants m⁻²; 1,866 seeds m⁻²). These treatment combinations were able to deplete the initial seedbank (1,748 seeds m⁻²) to manageable levels (< 5 seeds m⁻²) within 3 yr. The results of this study should provide growers with confidence that severe rigid brome infestations can be managed effectively without compromising crop productivity.

Nomenclature: Triasulfuron; trifluralin; rigid brome, Bromus rigidus Roth BRORI