Faster ground cover can improve yields

When it comes to canola seeding rate and row width, think of your crop as a solar panel. The faster the ground cover, the more the solar panel can produce.

Researchers found that canola yields are maximized with seeding rates that result in early ground cover that is maintained throughout the growing season. Canola can compensate for lower seeding rates with increasing branching and podding, but if that reduction slows canopy closure, or if wide row spacings do not fill in, then yield will be reduced.

The overall hypothesis of this research is that optimal seeding rate and row spacing affect seed yield in canola by maximizing the ground cover through the growing season.

The study had three objectives: (1) to determine plant distribution, survival, branching, ground cover, and yield in response to row width and seeding density; (2) to develop and apply image analysis techniques to track space occupied by individual plants over time in different planting arrangements; and (3) to study and validate plant growth responses to planting arrangements through simulation modeling.

Researchers used a replicated, factorial field experiment that varied seeding rate and row spacing over a wide range. They grew canola in 2 x 6m plots using equipment similar to field scale equipment. Trials were repeated at Saskatoon, Saskatchewan (dark brown soil zone, semi-arid climate) and Carman, Manitoba (black soil zone, sub-humid climate) from 2019 to 2022. Researchers note that drought and heat stress during these field trials resulted in below optimal seed yield in canola and may have influenced the results. Despite these stresses and sub-optimal yields, researchers believe these results are still valid as plant population effects often have greater proportional effects in dry years.

Results

To maximize yield in canola, growers should seed at least 60 seeds per square metre (5.5 per square foot) and have row spacing of 30cm (12 inches) or less. Canola was able to compensate for low seeding rates by increasing branching and number of pods, but this delayed flowering. The row spacing effect was minimal compared to seeding rate, however wider row spacings always trended to lower maximum yields than narrower row spacing.

Crop yield in canola is highly associated with the space that the crop canopy occupies over time. The highest yielding treatments were the ones that most rapidly achieved and maintained full canopy coverage. The practical agronomic message of this model is that canola yield is not able to compensate for reduced ground cover from poor stands. To manage canola for highest seed yield requires agronomic practices including seeding rates and row spacings, that result in rapid canopy closure.

Existing recommendations to establish five to eight seedlings per square foot with row spacings of 12 inches are adequate to achieve maximum yield.