Prevention is worth a pound of cure when it comes to a thin plant stand in your canola crop — because there really is no cure once the plants have emerged.
“There’s a number of different things you can do to prevent a thin plant stand, but as far as a rescue, there’s nothing that’s a magical fix once you don’t have those plants,” said Murray Hartman, oilseed specialist with Alberta Agriculture and Forestry.
In a typical year, a plant stand that’s below the recommended seven to 14 plants per square foot will knock down your yield, but there are other “repercussions for thin stands,” said Hartman, who spoke at canolaPALOOZA in late June.
“You might have a thin stand, and if it had been thicker, you might not have had to spray your herbicide a second time,” he said, adding that things like spray timing, swathing timing, and desiccation are also impacted by plant density.
And there’s no silver bullet for achieving that optimum plant density.
“It varies depending on the conditions. There’s not a magical number,” said Hartman.
“The first four or five plants per square foot are going to get you to about 90 or 95 per cent yield potential. But to get to that next five per cent, sometimes you have to double the seeding rate. That’s not really cost effective with the price of seed.”
In some cases, producers may not take into account the 1,000 kernel weight when seeding, he added.
“If you want to prevent a thin stand, take a look at the 1,000 kernel weight. Don’t get caught by having a much bigger seed and not adjusting for it.”
Emergence is another factor — one where “you often have no way of predicting what’s going to happen.”
“If your emergence has been less than you’ve expected, you might think about whether you’re seeding too deep or putting too much fertilizer in with the seed row,” said Hartman.
“Those are things that are actually killing the seed. You paid $12 a pound for the seed and then you’re going to kill it by seeding it too deep?”
Things like moisture at the time of seeding, disease, frost mortality, insects, herbicide residues, straw management and human error can all reduce emergence, he said.
“Now all of a sudden your effective stand is thinner than you expected, but you can go back and readjust how you’re managing some of those factors.”
Cut your losses
But once you’re facing poor growing conditions and poor emergence, often your best bet is to cut your losses, said Hartman.
“If you know there’s poor conditions early in the year and you know you’re going to get poor emergence, sometimes a thin stand is the more economic choice,” he said.
“If you’ve got 40 per cent emergence, you’re putting on a lot of seed and only 40 per cent of it’s coming up. And because it’s poor emergence, when you’re putting more seed in the ground to try to get up to a target density, you have to put a lot of seed in the ground.
“At that point, you have to be satisfied with a bit of a thin stand under these poor conditions.”
And sometimes, you can get a “really high yield from a really poor plant stand” — which was the case for many growers in 2015, when growing conditions started out poor but were “really good from midsummer on.”
“A canola plant senses its neighbours, so if it’s a thin stand, it’s got a lot of dormant buds when it’s under stress,” he said. “But then the rain comes and everything’s good. It’s going to start rebranching and flowering — and it can do that because it’s thin.
“As long as the season is long enough in the fall, all of a sudden you’ve got a better yield than if it would have been a thick stand.”
But that happens “the minority of the time,” he cautioned. “We can’t predict that at seeding time. But if it is poor conditions at seeding and you’re going to get poor emergence, you have to realize that a moderate seeding rate is going to give you a thin stand, and that’s kind of OK under those conditions.
“It’s just not economical to try and push up the seed costs so high.”