Scouting for disease, insects and weeds pays — and so does assessing plant stand establishment, says a Canola Council of Canada agronomist.
Getting a handle on emergence (and therefore seed mortality) can reveal which management practices aren’t working, said Autumn Barnes.
“If producers go out and get these numbers they can see, just as a potential example, that they only got 45 per cent emergence on a field where they bumped their seed-placed fertilizer, but got closer to 60 to 65 per cent emergence on some strips where they used their normal fertilizer rate,” said Barnes.
“That 15 per cent bump in emergence can really make a difference in terms of profit at the end of the day.”
But you need to write down your findings, said Jeremy Boychyn, an agronomist with Alberta Wheat and Barley.
“Knowing that gap (between mortality and emergence) is essentially a first step in addressing different management topics for seeding in the spring each year. As you do this consistently over the years you can start to build a knowledge base of how your seed is going to respond.”
Be random when sampling
As in field scouting, plant stand assessments require finding representative samples.
In order to reduce bias, sample randomly, said Barnes. When canola plants are at the two- to four-leaf stage, she walks a W-shaped pattern through a field throwing a Hula Hoop.
“I find it gives you a little bit of a randomness so you are not just drawn to the better or the worst parts of the field,” she said. “I’ll walk, toss the hoop, walk another 50 or 100 feet, toss another hoop and try to get, ideally, 15 to 20 spots within the field. But really the more samples, the better.”
A similar method can be used for wheat and barley, said Boychyn. If using variable-rate seeding, sample each “zone” in which you have used a different seeding rate, he said. Otherwise, walk a ‘W’ or zigzag pattern, sampling seven to 10 areas per quarter section.
“Take some kind of object — whether that be a shovel or a golf ball — and toss it behind your back,” he said. “Lay your ruler or tape measure from that spot to always a west direction or always an east direction so you’re not laying it based on where you want to lay it, which can add a preference towards what looks like a higher seeding area or a lower seeding area.”
The process isn’t entirely random as you should stay away from marginal areas such as low-lying high-salinity spots, he said.
“Pick areas that are representative,” said Boychyn. “Producers usually have a pretty good idea of what their fields look like so if you show them a map I bet they would be able to point and say, ‘This is a typical area of my field.’
“If you find there is a lot of variance in what is typical, then try and pick from both the lower-typical and higher-typical areas so you can average those.”
Parsing the numbers
The next step, of course, is to count plants and compare results against the establishment you planned before putting seeds in the ground. If you don’t do an exact count, you should at least have some idea of the consistency or variability of your stand establishment.
Then ask agronomists in your area or extension specialists what a reasonable emergence number would be, said Boychyn.
“Then you can really start to ask some questions,” he said. “If (your number) is lower than what you’re seeing in the area then you can ask yourself what may be presenting challenges to your seed that is reducing the amount of emergence.
“Are there field conditions that are reducing your ability to get a high percentage of emergence? Are your expectations too high? Are you encountering disease issues in the field or are your seed lots not as high quality as you need them to be?”
The answers are not always environmental, he added.
“It could be the tools you’re using. We calibrate (seeders) but they are not always going to work exactly the way we want them to. There are going to be challenges with them and sometimes they can be as simple as making adjustments on the seeder to make sure you are going at the right depth and seeding at the right rate.”
In addition to getting ideas for what to do differently next year, assessments also allow you to take immediate action on other fronts.
“If you seeded for 30 plants per square metre and you wound up with less than 20, you can anticipate more tillering and maybe more weed issues,” said Boychyn. “You may have increased risk of fusarium head blight. You may mix your fungicide a little different because of that.”
On the canola side, there are benchmark numbers on what stand counts should be at the two- to four-leaf stage, said Barnes.
“Generally speaking, the data that Alberta Agriculture and Forestry has crunched shows that at two to four leaf that five to eight uniform plants per square foot or about 50 to 80 uniform plants per square metre is a really good balance of risk and profitability or risk and economics,” she said.
“The lower you go the thinner your stand will be. Consequently, if you get over eight plants per square foot you’re going to get some self-thinning. Those are seeds that didn’t necessarily need to go into the ground.”
The more likely scenario, however, is thinner stands, said Barnes.
“At around three to four plants per square foot or 30 to 40 plants per square metre we see yield predictability and yield stability really start to drop off.”
However, that’s not a hopeless situation, she said. But you may need some patience and extra management.
“Canola is what we call a ‘plastic plant’ — it’s a really vigorous plant, especially our hybrids, and it can branch out and really perform even in challenging situations,” she said. “Sometimes you can get away with these suboptimal plant stands. Thinner stands are going to flower for longer so that means you are going to have less time for seed fill. They are going to mature a little bit later. Weed management is going to be a little bit more of an issue potentially.”