To investigate the interaction between three sowing methods/planting arrangements and herbicides on ryegrass control in wheat.

Wheat plant density was significantly affected by the planting arrangement (P=0.027) and the herbicide treatment (P<0.001). The Ribbon seeder system had the highest wheat density (196 plants/m²) as compared to the knife-point system (180 plants/m²) and the Zero row spacing (177 plants/m²). Wheat plant density in the inter-row space in the Zero row spacing treatment was reduced by Treflan + Avadex and Boxer Gold. Annual ryegrass plant density was only affected by the herbicide treatments (P<0.001). Pre-emergent herbicide activity was much lower than expected (24-29% efficacy) and is likely to be due to extremely dry soil conditions at the site (decile 1 growing season). Similarly, the reduction in ryegrass spike density by the herbicides relative to the untreated control was low and ranged from 6 to 24%. There was no significant reduction in ryegrass seed production by the herbicide treatment, which was surprising because Sakura and Boxer Gold did reduce ryegrass spike density. Ryegrass was able to produce 18-20,000 seeds/m² in different herbicide treatments, which highlights the poor efficacy of pre-emergent herbicide in dry conditions. Herbicide treatments had a significant effect on wheat grain yield with Sakura producing the highest yield (2.31 t/ha), closely followed by Boxer Gold (2.13 t/ha). Sakura and Boxer Gold treatments increased wheat grain yield by 29% and 19% compared to the untreated control, respectively.  These results show that ryegrass was quite competitive against wheat under the dry conditions experienced in 2018. The treatment of Sakura ($40/ha) increased wheat yield by 0.5 t/ha compared to the untreated control, which would have improved the gross margin by $150/ha.