There’s been a lot of discussion during the past couple of years on changing from seeding your standard four to five pounds per acre (canola) to focus more on what your target plant population should be. If you want to get the best yield and the best performance out of your canola hybrid, you really have to look at the field’s specific situation and the hybrid’s specific attributes.
The most important thing to remember is one size doesn’t fit all when it comes to what your target plant population can be. Indeed, there’s no ‘set it and forget it’ — if you’re really going for optimum yields, it can’t be cookie cutter.
For the most part, everybody is comfortable with targeting five to eight plants per square foot. But I always like to start with looking at the hybrid and what the suggested best seeding rate is for that hybrid. If you go out to any canola trial, you’ll see hybrids are quite different in their growth patterns and how they show up in the field. You should consider the hybrid you’re putting in the ground, talk to your seed company and learn about the characteristics of the hybrid and then, all considered, what the right seeding rate is.
There’s a significant amount of variation on how a hybrid displays in the field. For instance, there are hybrids with larger plants, larger stalks which branch out aggressively, and they could be more conducive to a lower seeding population. There are also other hybrids that will do better at a higher seeding population, given their plant structure.
When seeding and determining your target plant population, you should understand your hybrid, seeding conditions, climate, your seeding date and your soil moisture. For instance, if you’re going into cold, wet soils in the Alberta foothills and you have a high chance of an early frost, you should be looking at higher seeding rates. Some of the biggest risks when you look at stretching a bag of canola with a lower seeding rate is an early frost, high winds or other environmental factor which results in higher seedling mortality. In this case, you could end up with less than three or four plants per square foot. Indeed, if there’s any environmental factor that decreases your seeding rate to those lower seeding rates, you’re going to be into a zone where it could compromise your yields.
There are also risks both agronomically and financially to seeding at a higher rate than is optimum. With some hybrids, if you over-seed — and I’ve seen lots of plant populations in the teens — you obviously are spending more on seed than you need to. Besides the financial implications you can also affect the harvestability, the standability of the crop at those higher seeding rates. There are great hybrids that stand well, yield well and have good harvestability in the optimum seeding range, in that five to eight plants per square foot range. However, if you get into higher populations with those hybrids, you risk lodging and more disease pressure because you don’t have as much airflow in the canopy.
On the other hand, if you’re on the light side of the plant population – let’s say you’re targeting the lower end of the optimum range, i.e. about four to six plants per square foot — and you get any environmental event, whether it’s cold, wet soils, frost or anything that can reduce your plant population early in the season, you’re going to be into a plant population range that’s sub-optimum for yield and you can suddenly experience a major yield loss if you’re getting below three or four plants per square foot.
I really encourage growers to spend time thinking about plant populations and not take a one-size-fits-all approach. Every hybrid has a variation in seed size; and from hybrid to hybrid, there are large variations in agronomic characteristics. As mentioned before, you really need to target a plant population that fits the individual field’s situation and the hybrid’s situation.