Germination ecology of dwarf amaranth (Amaranthus macrocarpus): an emerging weed in Australian cotton cropping systems

Abstract

AbstractDwarf amaranth (Amaranthus macrocarpus Benth.) is a problematic broadleaf weed in many crops in Australia; however, no information is available on the germination ecology of this species. Seeds from two populations of this species were collected from Hillston, NSW, Australia (D-P-01), and Yandilla, QLD, Australia (D-P-02). Seeds were germinated at a range of constant (20 to 45 C) and alternating temperatures (30/20, 35/25, 40/30, and 45/35 C day/night). For the constant temperature treatments, the highest germination occurred at 35 C for D-P-01 (89%) and D-P-02 (82%). Germination was higher at the alternating day/night temperature of 40/30 C for both populations D-P-01 (91%) and D-P-02 (85%). Seed germination of both populations was stimulated by light, which indicates a great amount of emergence of A. macrocarpus can occur on bare ground such as crop seed beds. Results also revealed that this species tolerates a moderate level of salinity and can germinate in slightly alkaline soil conditions. The emergence of this species was highest (47%) for the seed buried at 0.5-cm depth in grey cracking alkaline soil compared with seed buried at the same depth in acidic red soils. These results suggest that soil inversion by tillage to bury weed seeds below their maximum emergence depth could serve as an important tool for managing A. macrocarpus. The results from this study will help in developing more sustainable and effective integrated weed management tactics for the control of this weed and weeds with similar responses in summer cropping systems.