Thicker stands improve weed management

Seeding canola at relatively high rates results in a more competitive crop. Current research shows both higher yields and improved weed management in crops seeded at a higher rate compared with lower rates of seeding.

Neil Harker of AAFC Lacombe et al published a paper in the Canadian Journal of Plant Science (2012) titled: “High-Yield No-Till Canola Production on the Canadian Prairies,” discussing a three-year project on plots in Alberta, Saskatchewan and Manitoba. Harker’s study compared higher-than-average input level combinations with lower-level combinations to determine which would increase canola seed and oil yields in relation to current production practices. Direct-seeded experiments were conducted on eight plots in canola-wheat-canola or continuous canola rotations. Plots were seeded at the rates of 75 and 150 seeds per square metre (or about 7.5 and 15 per square foot). Overall, high seeding rates increased canola yields by the equivalent of 1.3 to 2.9 bu./ac. over low seeding rates.

The paper concluded that, “High-yielding canola on the Canadian Prairies is likely to be grown in rotation with other crops, with more nitrogen than is currently recommended from soil tests, and with more than 75 seeds per square metre.”

In an earlier paper, also published by Neil Harker et al, results of a three-year field experiment at Lacombe and Lethbridge, AB show a 41 percent yield increase through a combination of high seeding rate and early weed removal. This Alberta study analyzed various cultivars, seeding rates and weed management through timing of weed removal to determine the optimal combinations with respect to canola yield and quality.

Hybrid and open-pollinated canola cultivars were seeded at rates of 100, 150 and 200 seeds per square metre (approximately 10, 15 and 20 per square foot). By weight, these rates averaged approximately 5, 7.5 and 10 lb./ac. for the hybrid cultivar and 3.5, 5 and 6.3 lb./ac. for the open-pollinated.

Based on this study’s results, seeding at the lower rate reduced yields by an average of seven percent across all sites, compared with the two higher rates. Typical current canola seeding rates, equivalent to approximately 5 lb./ac., translate to approximately 10 seeds per square foot for hybrid cultivars and closer to 15 seeds per square foot for open-pollinated cultivars, similar to the ones tested. Harker concludes that the combination of higher seeding rates, early weed removal and the use of a competitive cultivar leads to high levels of canola production.