By Canola Council of Canada
May 1, 2014 - Canola crops need at least five living and healthy plants per square foot to reach their full yield potential.
"The unfortunate thing is that many canola crops do not achieve this population, which means growers are potentially leaving money on the table," says Autumn Barnes, agronomy specialist with the Canola Council of Canada.
The ideal is to have seven to 10 plants per square foot emerge, leaving some margin to lose plants during the season to insects, disease and weather conditions, and still have enough plants to reach the yield potential.
Yet, the math suggests that with an average seeding rate of five lb./ac., a thousand seed weight of five grams, and a typical 50 per cent seed survival rate, the result is only 5.2 plants per square foot. "The number is even lower with heavier seed," Barnes says. "This doesn't leave much margin for error."
In order to keep seeding rates at five lb./ac. and also achieve seven to 10 emerged plants per square foot, the seed survival rate will have to increase.
This can be done with the following best management practices for canola seeding:
Seed shallow. Half an inch to one inch below the packer furrow is the recommended seed depth for canola. This will reduce days to emergence and reduce the seed energy required for emergence. This also reduces the number of weeds that are able to emerge ahead of the crop.
Seed at a consistent depth. The more consistent the better. For some drills, the overall average may be one inch, but the range could be zero to two inches. Too shallow or too deep both contribute to seed and seedling mortality, and those that do emerge from too shallow or too deep will have highly variable emergence dates, creating an uneven field.
Seed slower to ensure good and even seed depth from all openers. The ideal speed will vary by drill and soil conditions. In general, at higher speeds, rear openers tend to throw more soil over the front rows. Seed in these front rows will be buried deeper, making them slower to emerge — if they emerge at all. Re-check depth when moving from one field to the next.
Limit seed-placed fertilizer. Seed-placed fertilizer can damage canola seedlings. There can be safe low rates of seed-placed nitrogen in some cases, but the best practice is to save the spot in the seedrow for a maximum of 20-25 lb./ac. of phosphate and put other nutrients away from the seed row.
Penetrate trash. Spread residue evenly in the fall, and have a drill that can penetrate trash so all openers place seed uniformly into the soil.
Leave a firm seedbed. Openers that fracture the seedbed to place fertilizer lower than the seed may not provide the firm moist seedbed that canola needs. Worn openers that do not provide a defined seed ledge and high fan speeds that cause seed bounce can also reduce an opener's ability to place seed precisely.
Pack appropriately. In dry conditions, pack more to conserve moisture in the seed row. In wet conditions, reduce packing pressure to limit hard crusting. Packing pressure can be a delicate balance, and often changes by soil type as well as moisture conditions.
"Spring seeding season can seem rushed, but spending the time to place seed consistently at an optimum depth will improve seed survival and the return on seed investment," Barnes says.
A denser faster-canopying crop can also eliminate the need for a second in-crop herbicide application. It gives growers some added flexibility with disease and insect management decisions, knowing that losing a plant or two per square foot will not reduce yield potential. And a uniform plant stand of seven to 10 plants per square foot will mature quicker and more evenly, allowing for easier harvest management decisions.
"Taking time at seeding can pay dividends all season long," Barnes says.