Typically, broadcast seeding in canola is considered questionable at best. But it comes to mind when weather causes delays.
“Broadcast seeding is acceptable as a last resort late in the seeding season under wet conditions,” says Murray Hartman, oilseed specialist with Alberta Agriculture. “Wet soil can plug up openers and packer wheels, and the seedbed can be smeared, which impedes good seedling emergence.”
Since working wet fields can cause soil compaction, waiting is always the best option, unless it’s already near the end of May. “There are custom broadcast seeders,” Hartman suggests.
Making sure the crop is in on time may also be important in order to qualify for crop insurance deadlines. In Alberta, for instance, canola must be seeded before June 20 in order to qualify for yield insurance. It is recommended, however, that the crop is actually in the ground by May 31, otherwise grade coverage could be limited.
Crop insurance actually depends on establishment, says Hartman. “Broadcast canola does not automatically quality for crop insurance,” he says. “The established stand may need to be inspected and meet crop density standards before it can be insured. If the crop does not grow and the ground is too wet to seed, the grower could be eligible to receive an unseeded acreage benefit. Rules for unseeded acreage benefits vary by province.”
The good news is that establishment is somewhat controllable, especially if certain situations are avoided. For instance, avoid planting into fields with poorly distributed heavy crop residue, or into fields that require large amounts of fertilizer. Hartman says they make poor choices because nitrogen, phosphorus, and potassium efficiency suffers greatly when left on the surface.
On average, yields on broadcast-seeded fields will be five to 10 percent less than fields that are drill-seeded. “In wet conditions, broadcast seeding can equal or better drilled methods if there is more than two or three weeks delay needed to achieve the drilled seeding,” says Hartman.
Tips for broadcast success
Hartman says that broadcast seeding should only be considered if it is already late in the seeding season and wet weather has greatly delayed seeding progress. Fields should be harrowed soon after seeding to cover the seed and fertilizer.
Often, germination and seedling emergence rates for broadcast canola are lower as compared to seeds that are drilled into moist-packed seedbeds. A higher seeding rate can compensate for this. “It also provides more margin for error if the seed and fertilizer ratio doesn’t stay consistent as the floater tank empties,” says Hartman. “A floater with two tanks — one for seed and one for fertilizer — should eliminate this particular risk. Consider seed size in grams per 1,000 kernels and estimate seedling survival when setting the seeding rate.”
Fields with poorer conditions are better suited to lower-priced seed in order to allow for increased seeding rates and the higher risk of crop failure.
Fertility practices will differ with broadcast seeding, too, says Hartman. He suggests doubling the phosphorus rate, since canola needs early access to phosphorus and phosphate drills and seed are not always close enough for timely access to fertilizer. Hartman warns growers to account for higher nitrogen losses — broadcast nitrogen has a higher risk of denitrification. On saturated soils, nitrogen fertilizer efficiency can be especially reduced.
“Enhanced efficiency nitrogen fertilizers, such as ESN or Agrotain, will reduce these losses,” he says. “Although harrowing after broadcasting is still recommended to get these fertilizer products into the ground.” Although this can increase overall costs, it may be worth it in less ideal conditions. Apply the blended seed and fertilizer as soon as possible after blending or utilize a floater with two tanks, one for fertilizer and one for seed.
Consider a split fertilizer application, says Hartman. Broadcast seed first and see what gets established; if the crop gets established, then top up with broadcast nitrogen and sulphur, he says. Top dressing applications should also be made as soon after emergence as possible, he continues, since early nutrient access is important for optimal yields.
Finally, if weeds are an issue and there’s considerable growth in the field, a herbicide application should be made pre-seeding to prevent weeds from adding to fertilizer losses. “Canola seed laying on the surface can be affected by some herbicides used in herbicide tolerant canola,” he concludes. “This is another reason to harrow after broadcast seeding.”
While broadcast seeding certainly isn’t first on the list of recommendations, it does provide an additional option. And with proper management it is possible to obtain adequate yields.