The interaction between seeding rate and row spacing of hybrid and open pollinated canola (Brassica napus) varieties on annual ryegrass (Lolium rigidum) growth and seed production.

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The trials located at Miling and Kojonup in the grainbelt of Western Australia investigated combinations of canola variety (hybrid or open pollinated), crop row spacing (25 or 50cm) and canola seeding rate (20, 35 or 50 plants/m2). The average seedbank at the Miling and Kojonup sites were 3,630 seeds/m2 and 23,240 seeds/m2 respectively. Annual ryegrass (ARG) establishment was reduced in hybrid canola treatments seeded at narrower 25 cm row spacing. Decreasing crop row spacing (from 50 to 25cm) and increasing canola seeding rate (from 20 to 50 plants/m2) was found to reduce ARG establishment in the absence of herbicides. At the Kojonup site, ARG seed production was reduced by hybrid varieties (Trophy) and higher plant densities (50 plants/m2). However due to the low rainfall at the Miling site, no interactions were identified. Canola yield in this study was increased in hybrid variety (Trophy) treatments especially at higher seeding rates (50 plants/m2). Interestingly, however, canola seeded at the wider row spacing (50cm) consistently out yielded the corresponding variety and seeding rate combination at the narrower 25cm row spacing. This study conducted two trials in 2018 (Mingenew and Cunderdin) and 2019 (Miling and Kojonup). Multi- environment trial analysis for the combined 2018 and 2019 data to be completed.