The Effects Of Row Spacing and Seeding Rate On Weed Competition and Yield In Organic Canola Production.

Weed competition is a major concern in organic canola production.  Increasing seeding rates and widening row spacing to allow for between row cultivations may serve as mechanisms to reduce weed competition.  This study was conducted to evaluate the interaction of row spacing and seeding rate on yield and weed pressure in organic canola production. Canola variety ‘Hornet’ was planted at five seeding rates (3.4, 6.7, 10.1, 13.4, 16.8 kg ha^-1) at three row spacing’s (17, 34, 68 cm) in Goldsboro, Kinston, and Salisbury, NC in 2011 and 2012. In 2013, all locations received between row cultivations in the 68 cm row spacing. Averaged over locations, seeding rate had little effect at the 17 cm row spacing but was negatively correlated with yield at the 34 and 68 cm row spacing's. Row spacing also had a significant effect on weed coverage (P=0.0299), and coverage was lowest in the 68 cm rows. Fall and spring stand count results show that wider row spacing at higher seeding rates led to more plants per linear meter but despite these results lower yields were obtained with wider row spacing at the highest seeding rates. Increased disease pressure and intraspecific competition are possible causes. At each seeding rate, narrow rows had the highest number of plants ha^-1 in both the fall and spring stand counts, showing that thinning of the wider rows occurred rapidly.  Results indicate that producers have flexibility with row spacing options for organic canola production, and seeding rate selections should be made based on desired row spacing.