Disclaimer: Canola Watch content is research-based, but broadcast canola seeding is not a well-researched practice. Tips in this article are based on experience. We share these tips because broadcast seeding is often considered in years when excess moisture delays timely seeding of the crop using “normal” well-researched seeding practices.
Best results for rapid and uniform canola emergence tend to come when seed is placed 1/2” to 1” deep into warm, moist soil and packed lightly. However, broadcast seeding can work in a pinch when the calendar ticks toward June and fields are still too moist for a farm’s regular seeding tool.
Here are a few tips:
Timing. Broadcast seeding in late May could have higher yield potential than waiting two weeks for ground to support the drill. Manitoba crop insurance data show that canola seeded in Manitoba the first week of June yields 90% of average. Another interpretation is that field conditions still have time to improve and allow for “regular” seeding and decent yield potential. If by late May or early June broadcast seeding still appears to be the best solution for wet fields, the warmer soils should result in rapid germination and establishment of the seedlings, with less risk of mortality from cool soils or frost damage.
Seed rate and seed survival expectations. Seed germination and seedling survival for broadcast canola could be lower than for seed drilled into a moist, packed seedbed – but not necessarily. In the Canola Council of Canada’s Ultimate Canola Challenge site in Manitoba in 2013, one team of experts in a three-team competition chose to broadcast onto moist, warm soil, and had exceptional seed survival. It may be worthwhile to set a broad range of expectations. With a seeding rate of 10 seeds per square foot, low emergence of 20 per cent will result in two plants per square foot. Not great, but not a disaster – as long as the stand is relatively uniform across the field. (A related study on canola reseeding found that an established uniform canola stand with as few as two plants per square foot generally had higher economic potential than a thicker stand reseeded late.) If emergence is 80 per cent, the population will be at the top end of recommended target of five to eight plants per square foot. This higher plant population has the benefit of earlier maturity.
Equipment. Ag retails and some farmers have floaters or Valmar-based applicators, which use air to deliver product through a boom (usually 60 to 70 feet). These same tools can broadcast canola seed. Some applicators have multiple compartments, each with their own meters, to apply fertilizer and seed at the same time. Floaters can cover a lot of ground quickly. Another option is a regular air drill with openers lifted out of the ground. This still requires fields firm enough for travel, but it avoids the drag and “mudding in” from having the openers engaged with the soil. If fields are iffy for firmness, farms could run with seed only – to reduce weight – and go back later to apply fertilizer.
Talk to the operator. Canola seeded with a floater or Valmar-based applicator is not common practice, and operators may have little to no experience seeding canola. Applied at such low rates, canola presents a metering challenge when run on its own through a separate bin and meter. The grower may want to be there for the first field to check the seed bin after the first few acres. If the operator is seeding a lot of acres, ask if they have checked for plugging throughout the airflow distribution system.
Fertilizer. A good-yielding crop needs fertilizer. A grower could take a chance and skip fertilizer, hoping to bank on a decent supply from soil reserves, but that hope rarely turns into happy results. Consider these fertilizer practices for broadcast canola:
- Apply the recommended rate of phosphorus. Canola plants need early access to phosphorus. When broadcast, phosphate prills and seed are not always close enough for timely access to the fertilizer, so the “starter” rate of phosphorus is not enough. Farmers can use the full recommended rate when broadcasting. Canola with phosphorus often gets off to a quicker start, which can reduce days to maturity. A Westco Fertilizers study (Karamanos et al, 2001), which compared broadcast and row-seeded canola at six sites in Alberta from 1997 to 1999, showed a yield benefit from adding phosphorus fertilizer. However, it concluded that even when canola was broadcast seeded, phosphorus placed in a band was more effective than when broadcast. Broadcast canola with side-band phosphorus yielded 9.4 bu./ac. higher than canola without any phosphorus fertilizer, while broadcast canola with broadcast phosphorus yielded 7 bu./ac. higher than canola without any phosphorus fertilizer.
- Use urease and nitrification inhibitors for nitrogen. Broadcast nitrogen has a higher risk of loss, especially when applied on very moist soils. Combination products with urease and nitrification inhibitors are a good choice to protect the nitrogen in this situation. Consider a slightly lower than recommended nitrogen rate (perhaps 85 to 90 per cent of soil test recommendation) for canola broadcast in late May or early June. The full rate of nitrogen could extend the required days to maturity. More on urease and nitrification inhibitors.
- Seed soon after blending. When seed and fertilizer are blended days prior to application, fertilizer could reduce canola seed viability. At the Manitoba Crop Diagnostic School in 2009, Manitoba Agriculture staff ran an experiment to test canola seed germination after blending with fertilizer. A day or two showed no significant effect on canola germination, but ammonium sulphate was particularly damaging when left for any longer. (See the graph below.) Fertilizer prills are also abrasive and can remove some of the canola seed treatment. Again, this is especially true for ammonium sulphate. Ammonium sulphate blended with canola seed will often take on a blue tint – suggesting a high rate of abrasion. Ammonium sulphate also has an affinity for moisture and can increase plugging in humid conditions. One benefit to blending phosphorus or urea with canola seed is that it bulks up the canola seed, which could make application rates a little less finicky – especially for operators with limited experience floating canola seed (which could be most of them).
- Consider a split fertilizer application. Growers could broadcast their seed first, then top up with appropriate forms of nitrogen and sulphur if the crop gets established. However, early access to nutrient is important for optimal yields, so top dressing applications should be made as soon as possible after emergence.
- Broadcast nitrogen and sulphur, then drill seed. If the key barrier to using the drill is the risk of getting stuck when pulling a fully-loaded cart, growers could broadcast their nitrogen and sulphur, and use the drill just for seed and phosphorus. That way, they wouldn’t have to fill the seeder tank right full, which could make it possible to get the drill through a field without getting stuck. If nitrogen is broadcast, always use an inhibitor to reduce nitrogen losses.
High residue increases risk. Successful broadcast seeding requires good seed to soil contact. This may not be possible in fields with lots of straw cover. With a thick layer of thatch, seed and fertilizer are not getting down to the soil surface. Spring cultivating ahead of broadcasting could create an equally inhospitable seedbed, with large clods and a crusted soil surface. Fields with thick residue that are too wet for a cultivator or harrows probably shouldn’t be broadcast seeded. Seed can germinate in moist residue, but seedlings are not anchored, so can dry up and blow away in the wind.
Cultivate or harrow after seeding. Shallow cultivation or harrowing (if cultivation is impossible due to wet conditions) will improve seed to soil contact in a field that has been broadcast seeded. Avoid creating lumps or clods during cultivation or straw piles with harrows or cultivators. The ideal harrowing pass will run on a right angle to the floater pass to spread out the seed and fertilizer. For this reason, harrow after the floater leaves the field – rather than “chase” the floater through the field.
Seeding with a plane or helicopter. Pilots can do it, but if the field is too wet for a floater, it will be too wet for harrows and sprayers. Fields should be harrowed after broadcast seeding to loosen the soil surface and provide seed to soil contact. This is especially true for seed broadcast onto stubble. Crop residue can be a barrier preventing seed to soil contact. Canola seed is very light and does not embed into the soil, even if dropped from an airplane at high speed. Aerial seeding also requires ground-based fertilizer application. The critical time for fertilizer application is within five weeks of crop emergence – so there is time. (Canola Watch talked about aerial seeding in 2011.)
Careful with weed control timing. Seeds on the soil surface are highly vulnerable to herbicide. Do not apply post-seed/pre-emergence glyphosate on Liberty Link and Clearfield canola varieties that have been broadcast and remain on the soil surface. Roundup Ready varieties can tolerate glyphosate at this early stage.
Crop insurance. Consult with provincial crop insurance for rules and eligibility related to broadcast seeding. Here are the basic rules, as of May 2022…
- AFSC in Alberta: AFSC clients broadcast seeding canola should be aware that if a field fails to establish or meet the minimum number of plants, which is two per square foot for hybrid-type canola – and this is not due to an insurable reason such as seeding method, the field will not be covered.
- SCIC in Saskatchewan: SCIC expects producers who may be considering alternative seeding methods like broadcast and harrow to follow recommended seeding practices. If the crop fails to establish, compensation will not be available. Crops which successfully establish are eligible for ongoing yield-loss coverage. For more information by area, or how recommended seeding deadlines may impact coverage, contact the local SCIC office.
- MASC in Manitoba: In order for broadcast and aerial seeded crops to be eligible for insurance: (1) Seed must be incorporated into the soil by mechanical means on or before the associated seeding deadlines for that crop. MASC will consider the date of incorporation to be the date of seeding. (2) Crops seeded by broadcast or aerial methods must fully establish in order to be eligible for AgriInsurance.
Yield expectations. Canola Watch reported on yield results from broadcast seeding in 2010 and 2011. This is what we wrote back then: “Experience from the past two years of wet conditions in the eastern Prairies has shown that, in general, growers who tried broadcast or aerial methods to get fields seeded had issues all season long with thin stands, uneven maturity, weed control, low fertility and poor yields. Best results from broadcast seeding came from fields that were fertilized early and harrowed to improve seed to soil contact.” We then added that if field conditions allow for follow up passes to harrow and apply fertilizer, it means the fields could also soon be ready to seed with the drill. Older studies took a scientific approach. A Westco Fertilizers study (Karamanos et al, 2001) compared broadcast and row-seeded canola at six sites in Alberta from 1997 to 1999. It concluded that row-seeding canola resulted in a significant yield advantage of 0.18 to 0.58 tonnes per hectare in four of the six experiments and no significant difference at the other two. (The yield advantage for row-seeded canola at the four sites was approximately 3 to 10 bu./ac., based on canola yielding around 50 bu./ac.). Another from 1977 (Clarke et al) compared broadcast and “drilled” canola head to head. Drilled canola had a yield advantage, but broadcast results were still pretty good.
Farms still a couple of weeks away from seeding with a drill may want to inquire about a floater as backup just in case further weather delays make drill seeding impractical.