1. The challenge
Plant density and canola yield aren’t strongly correlated, so optimum stand density is about risk management and is somewhat subjective. The Canola Council of Canada has long recommended a target plant density of seven to 10 plants per square foot at emergence to optimize agronomic benefits and provide a consistent baseline for balancing risk and profit. As seed costs have gone up, growers are trying to save money by seeding at lower rates. Emergence surveys show an average around four to seven plants per square foot. Additionally, most farmers don’t target a stand density at all and fewer count plants at emergence to see how close they came to achieving their goal.
2. The risks
Growers who don’t set a target plant density have no idea where they may be losing or winning in the seeding operation. Should you be putting more seed in the ground? Could you save some money and lighten up your rates in a given field? Without a target density and ‘report card’, growers can only guess at these answers. This is arguably the most risky scenario and I strongly advise growers to re-assess this practice for the 2017 growing season.
Choosing the wrong plant density target can carry its own risks. Growers who seed too heavy spend more money on seed than necessary and miss out on profit. While this isn’t as common as seeding too light, it does happen and the profit is still unrealized. Growers who seed too light open themselves to a whole host of issues:
Poor spring conditions could push emergence lower than 40 per cent and leave an even thinner or more variable stand that compounds issues like spring frost, flea beetle damage and lower weed competition (especially if in an area with herbicide resistance).
- A thin stand has more branches and often flowers longer, making it difficult to stage for fungicide.
- Harvest will be more difficult to stage.
- Additionally, more stalks can help anchor swaths in the event of fall winds.
- If that isn’t enough to make growers reconsider canola seeding rates, don’t forget that our current insect thresholds and fungicide spray recommendations are based on uniform stands of seven to 10 plants per square foot. Pest management practices may need adjustment with a thin and/or non-uniform stand.
3. The solution
Planning ahead and collecting plant density data in-season can seem like a chore but it can prevent unnecessary risk and potentially save a lot of money. In a survey done in 1992 by Alberta Agriculture, almost 90 per cent of growers did not set targets for a specific plant population. Twenty-five years later, I’d be surprised if that number was much lower.
In 2017, all canola growers should be setting a target plant density for each field. Growers who value crop competition with weeds and uniform, quicker-maturing stands will probably opt for eight to 10 plants per square foot. Growers who want to take on more risk or are seeding into warm, moist soil with low risk of spring frost might want to try pushing a little lower to six plants.
Regardless of the density target, calculate a seeding rate based on that target and the seed weight (thousand seed weight can vary from 4-8 grams and drastically impact the number of seeds planted per square foot), then record it. Don’t forget to count plants at emergence. If not happy with results at the end of the year, bump up density plans for 2018. Or, if a thicker stand didn’t offer an advantage, consider why. Growers in that situation may want to seed some test strips or fields a little thinner in the future.
4. Options for creating an optimum stand
Buying more seed is probably the easiest way to increase the number of plants growing in a given area, but many free (or cheap) ways can make the most of the seed put in the ground. Incorporate a few of these ideas (or better yet, all of them!) to improve canola stand establishment without breaking the bank:
- Set plant density and emergence percentage targets prior to seeding, then follow up to see if targets were met. Understand why/why not.
- Keep seeding equipment well maintained and replace worn openers.
- Check soil temperature throughout the spring prior to seeding. Canola germinates quickly and evenly at temperatures above 8°C.
- Have a residue management plan in the fall for all of crops and seed canola into uniform field conditions.
- Seed shallow. If having problems getting uniform placement, try slowing down.
- Seed slowly. There is no ‘right speed’ for canola. Limitations will be set by equipment and conditions in each field.
- Check seed and fertilizer placement regularly and make adjustments as needed.
- Only place a maximum of 20 pounds of phosphate with the seed. All other nutrients do not need to be in the seed row.
- Consider replacing seeding implements if unhappy with placement and emergence (and it isn’t operator error).
- Get comfortable calibrating seeding implement. Consult
the owner’s manual and calibrate often.
5. Costs and ROI
The return on investment for seed can be difficult to identify until harvest time, marketing time or when future weed problems rear their ugly heads (or not).
We know that for every dollar of nitrogen applied, growers should expect a minimum $2 return, but investment in canola seed isn’t as black and white. Should a dollar of seed return a dollar of profit? Do the agronomic benefits of more seed outweigh the cost? The return on investment for seed can be difficult to identify until harvest time, marketing time or when future weed problems rear their ugly heads (or not). In some years, a given field can do quite well with lower plant densities. In others, it will suffer yield losses and set back weed, pest and harvest management progress.
Growers should identify their appetite for risk and try to place a dollar value on agronomic factors like increased weed competition, shorter flowering window, and earlier harvest before seeding each canola field. With the rising cost of seed, plant density targets aren’t going to be one size fits all in the future: power and profit are there to be realized for growers willing to invest time and effort understanding how density impacts different factors in their farming operations.