Row Spacing and Seeding Rate Effects on Canola Population, Weed Competition, and Yield in Winter Organic Canola Production

Abstract

Increasing seeding rate and widening row spacing to allow for between row cultivation may reduce weed competition in organic canola (Brassica napus L.) production. Research was conducted to evaluate the effects of row spacing and seeding rate on canola population, weed competition, and yield in organic canola production. Canola variety Hornet was planted at five seeding rates (3.4, 6.7, 10.1, 13.4, and 16.8 kg ha−1) at three row spacings (17, 34, 68 cm) in Goldsboro, Kinston, and Salisbury, NC, in 2011 and 2012. Between row cultivation was performed in the 68‐cm row spacing as weather permitted. Canola population increased with increasing seeding rate across all row spacings, and canola populations were highest with the 17‐cm row spacing, followed by the 34‐ then 68‐cm row spacings. Yield was similar across row spacings at the lower seeding rates in five of the six environments. At these environments, yield tended to increase in the 17‐cm row spacing as seeding rate increased but declined in the 68‐cm row spacing with increasing seeding rate. In one environment with a unique weed community, weed suppression and yield were higher with the 68‐cm row spacing. It was concluded that the yield plasticity of canola will provide producers flexibility in selecting row spacing, and seeding rate selections should be based on desired row spacing.Core Ideas Increasing canola seeding rate and widening row spacing to allow for between row cultivation may serve as mechanisms to reduce weed competition in canola production, but have rarely been evaluated in organic production. This study was conducted to evaluate seeding rate and row spacing effects on weed competition and yield in organic canola production. Despite different canola populations across canola row spacings, yield tended to be similar at low seeding rates across the row spacings indicating canola has the ability to compensate for low population. Depending on the weed species at your environment, widening row spacing to allow for between row cultivation may prove critical for reducing weed competition and increasing canola yield. Yield tended to increase with increases in seeding rate at the 17‐cm row spacing, however yield declines were observed with higher seeding rates in the 68‐cm row spacing, which is likely attributed to intraspecific competition. Organic canola producers have flexibility when selecting row spacing and seeding rates due to the great plasticity of canola.