Differential germination response of Navua sedge (Cyperus aromaticus) populations to environmental factors

Abstract

Navua sedge (Cyperus aromaticus) is a hard to control C4 perennial weed species in tropical regions of Australia. Knowledge of its seed biology could help to develop integrated weed management programs for this species. This study was conducted in laboratory and screenhouse conditions to evaluate the effect of alternating day/night temperatures, light, pretreatment high temperatures, burial depth, and flooding depth on the germination and emergence of two populations (Ingham and Tablelands) of C. aromaticus. Both populations germinated at temperatures ranging from 20/10 to 35/25 C; however, the Ingham population germination (76%) was greater than the Tablelands population (42%) at the highest temperature regime (35/25 C). None of the populations germinated at 15/5 C. Darkness completely inhibited germination in both populations, suggesting that the seeds are positively photoblastic. Seeds (dry and wet) of both populations germinated after exposure to pretreatment temperatures of up to 100 C for 5 min. After pretreatment at 150 C, only the Ingham population germinated, and the germination of dry seeds (62%) was greater than wet seeds (1%). None of the populations germinated after the exposure to 200 C. For both populations, maximum germination was observed for seeds at 0 cm, and a burial depth of 0.5 cm completely inhibited emergence of the Tablelands population and 2.0 cm inhibited germination of the Ingham population. A flooding depth of 10 cm greatly reduced emergence in both populations compared with 0 cm (62 and 78%) but 12 to 14% of seedlings still emerged, suggesting the need to integrate flooding with other management tools. The results also suggest that the Ingham population may have a greater potential to spread into new areas or become more invasive than the Tablelands population. Knowledge gained from this study can be used to manage C. aromaticus by fire/burning, tillage, and flooding.

Seed biology of alkali barnyardgrass (Echinochloa crus-galli var. zelayensis) and junglerice (Echinochloa colona) for improved management in direct-seeded rice

“…The growth of several weed species can be inhibited by flooding; however, the extent of inhibition differs among species (Chauhan 2021;Chauhan and Johnson 2008;Johnson 2009a, 2009b;Driver et al 2020). We observed that flooding did not kill E. crus-galli seedlings once they had emerged, but this was not the case for E. colona seedlings.…”

Utilization of the Neighborhood Design to Evaluate Suitable Pasture Crops and Their Density for Navua Sedge (Cyperus aromaticus) Management

“…These seeds disperse through various means, such as wind, animals, and machinery, while the extension of the rhizome and the dispersal of rhizome fragments during harvest and tillage can also introduce populations to uncontaminated areas [1]. Navua sedge seeds can germinate and thrive in a wide range of temperatures, soil moisture, salinity, and pH levels [2,5]. This flexibility further emphasizes the significant concerns posed by Navua sedge populations for farmers.…”

“…However, mechanical weed control is unsustainable, being less effective, necessitating regular repetition, and promoting seed spread to surrounding areas [2,6]. Tillage has been considered effective in burying seeds deeper into the soil [4], as the Navua sedge seed bank is primarily concentrated within the top 0 to 5 cm layer of soil, and Navua sedge seeds require exposure to light for germination [5,8]. However, this practice may prolong infestation by extending seed longevity in the soil seed bank and reducing seed losses [3].…”