To investigate factorial combinations of sowing time, seed rate and herbicides on the management of annual ryegrass in faba beans.

A field trial was undertaken near Winchelsea, VIC to investigate the effect of faba bean sowing time, seed rate and herbicide treatments on annual ryegrass (ARG) control. ARG plant density was unaffected by the seeding date but was significantly influenced by the herbicide treatments. The results of seed production were somewhat surprising. As expected in such a long growing season, the use of pre-emergent treatment of Simazine + Triflur X IBS was unable to provide adequate weed control and resulted in the highest ARG seed set. The results also show that the post-emergent application of Select and Factor were relatively ineffective when used in TOS 1. However, the post-emergent treatments were highly effective in TOS 2. Previous research has shown reduction in the efficacy of these herbicides under cold and frosty conditions as in this study. Crop seed rate had a significant effect on faba bean grain yield (P<0.001) but time of sowing did not influence grain yield (P=0.61). Grain yield increased significantly as seed rate increased from low (4.65 t/ha), medium (5.96 t/ha) to high seed rate (6.51 t/ha). At this high rainfall site, simply relying on pre-emergence herbicides proved inadequate. Simazine + Triflur X had a significantly lower grain yield than faba beans sprayed with a combination of pre- and post-emergence herbicides. Even though the highest ARG plant density present at the site was 33 plants/m2, it was quite competitive with the crop (P=0.01) and reduced its yield by 0.4 t/ha as compared to the treatments where Select or Select + factor were used as post-emergent treatments.