Germination ecology, emergence dynamics, and competition in feathertop Rhodes Grass (Chloris virgata Sw.): Implications for effective control strategies

Feathertop Rhodes grass (Chloris virgata Sw.) is a summer growing grass weed that is invading farming land in southern Australia, being favoured by conservation farming systems and weed management using a narrow range of herbicides. Improved understanding of the biology of this species will be important for its effective management. A series of experiments on seed germination, dormancy release and emergence pattern were conducted under laboratory, glasshouse, and field conditions at Wagga Wagga Agricultural Institute. Seed of feathertop Rhodes grass exhibited post-harvest dormancy but germinated after a 3-month after-ripening period. Soil moisture was critical for the emergence of feathertop Rhodes grass in both a sandy loam and heavy clay soil. Higher emergence levels occurred in the sandy loam, but seedling survival was higher in the heavy clay soil. Seeds buried at shallower depths had a high probability of emergence and emerged within 1-3 days, with more than 70% of seed emerging within 7 days from burial at depths of 0- and 2-cm. Seed of feathertop Rhodes grass can germinate early in spring in southern NSW but compete poorly when emerging in an established cereal crop. In a fallow situation, there can be staggered emergence of feathertop Rhodes grass, triggered by the rainfall events. Our results indicate that feathertop Rhodes grass might not be a problem in cereal cropping in southern NSW. Effective management should focus on winter and summer fallows. Strategic cultivation could be a useful control tactic for feathertop Rhodes grass management. Exposure to either paraquat or glufosinate herbicides reduced seed viability, depending on the application timing. Our study provides important information on the growth, development, and seed biology of feathertop Rhodes grass that will contribute to the development of a more effective management program for this weed in southern Australia.