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 (ClearfieldTM 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.

Field experiments were conducted at Warooka and Rudall on the Yorke and Eyre Peninsula of South Australia during 2004 and 2005 to investigate the effectiveness of metribuzin for the selective control of rigid brome in no-till sown barley. Metribuzin (135 to 203 g ai/ha) incorporated by sowing (IBS) was more effective in controlling rigid brome (> 67%) than the same herbicide dose applied POST. Although IBS metribuzin at the highest rate (270 g/ha) provided effective weed control (82 to 90%), it was more phytotoxic to barley, reducing crop density by 23% relative to the nontreated control at Rudall. Soil at Rudall had low clay and organic matter content. In contrast, tank mixtures of metribuzin (203 g/ha) with pendimethalin, applied IBS, provided reliable rigid brome control (89 to 93%) and resulted in little crop damage (< 5%). Over the site-by-year combinations studied, all herbicide-treated barley at Warooka and Rudall yielded 6 to 50% more grain than the nontreated crop. Although metribuzin provides growers with an opportunity to selectively control rigid brome in no-till barley, high rates (≥ 203 g/ha) of this herbicide on sandy textured soils can result in significant crop damage.