To investigate the effects of crop row spacing, seedbed utilisation and pre-emergent herbicides on ryegrass management in wheat.

The herbicide treatment had a significant effect on ARG density (P<0.001) in this field trial at Minnipa. Favourable rain events in June were highly suitable for the activity of both pre-emergent herbicides investigated in this trial. Averaged across the row spacing and SBU treatments, Boxer Gold and Sakura + Avadex reduced ARG plant density by 88% and 90%, respectively. The density of ARG spikes was significantly influenced by the herbicide treatment.  Boxer Gold reduced ARG spike density by 74% compared to the untreated control, whereas Sakura + Avadex caused 85% reduction in ARG spike density. The density of ARG spikes in Sakura + Avadex were significantly lower than in the Boxer Gold treatment. ARG seed production was also significantly affected by the herbicide treatment (P<0.001) but not by wheat row spacing (P=0.272) or seed boot design (P=0.994). ARG produced 5740 seeds/m² in the untreated control, which was reduced by 74% by Boxer Gold and 86% by the mixture of Sakura + Avadex. Presence of ARG at 190 plants/m² in the untreated control, reduced wheat grain yield by 11% compared to Boxer Gold or 8% compared to Sakura + Avadex. However, it was still profitable to control ARG with effective herbicide treatments. Based on cash grain price of Australian Premium Wheat (APW) of $400/t in 2018, Boxer Gold would be expected to increase the gross margin by $68/ha as compared $12/ha increase for Sakura + Avadex.