Seed vigour | ‘Better than average’ seed required to seed early, says Bruce Carriere of Discovery Seed labs
Cereal seeds are not as temperamental as canola seeds.
They tolerate slightly lower soil temperatures, which makes them the first choice for early seeding.
However, that’s not a green light to ignore good agronomic practices, says Bruce Carriere, owner of Discovery Seed Labs.
“Early seeding of cereals is not a great idea in my opinion. Several things can go wrong,” Carriere said, although he knows it’s a fact of life that producers always want to go early.
“If seed vigour is high and they sit there in the soil for a week, we’ll see just a little bit of mortality. But if cool soil temperatures continue much past a week, the plants really start to struggle once they emerge and the weaker plants will be susceptible to all kinds of stress throughout the growing season. Soil temperatures should be at least 4 C, so that’s really not much lower than the minimum recommended temperature for canola. The optimal temperature for cereals should be closer to seven degrees.”
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Spring temperatures do not rise on an even upward continuum, said Carriere. Some days are 20 C and then the nighttime temperature falls to – 6 C. There are also intermittent cold spells.
The top one inch of soil follows those patterns, ranging from 20 C down to sub-freezing temperatures day or night.
That’s why temperature readings should be taken at a depth of three inches.
Carriere said seed quality is also a factor.
“You absolutely must have better than average seed if you’re thinking about seeding early,” he said.
“You do not want high germ with low vigour. Low vigour seed will not perform in those earlier cooler soils unless you bring your seeding rate up to the vigour number. For example, if you have germ of 95 and vigour of 80, then you’d better be seeding with that vigour number in mind, not the germ number.”
Carriere said growers who push the date on cereals have only two options if they hope to succeed: buy seed with a high vigour number or increase the seeding rate substantially.
Cereals typically don’t suffer the kind of high mortality experienced by canola in normal conditions at recommended soil temperatures.
For example, a cereal grower who wants 30 plants per sq. foot uses the regular formula of calculating the 1,000 kernel weight and subtracting four percent for morality. Carriere said that provides the number that’s used for a seeding rate when soil temperature is close to the recommended 7 C.
“If you plant seeds in the spring for 30 plants per sq. foot, that’s how many seeds you can expect to emerge and grow. And at harvest, you should still see 30 plants per sq. foot unless there’s been a major disaster,” he said.
“But you can’t use that formula if you put seed into cold soils. You must use the vigour number to figure out your seeding rate, not the germination number.”
Carriere said there’s a big difference between seed vigour and plant vigour.
Plant vigour is a genetic quality of the variety. Some varieties have greater vigour than others and are consequently more suited to the stress of early seeding. He said there’s no way to test for plant vigour.
The test for seed vigour takes 11 days, so turnaround time can be fairly quick when assessing seed viability.
Although seed treatments have improved tremendously in recent years, Carriere said there’s a new issue that reduces their efficacy.
“Coverage on the seed has become more important than the chemical itself. The old adage of, ‘a little dab will do ya’ is not true anymore when we talk seed treatments. If you can’t guarantee 100 percent coverage on the seeds, don’t even bother treating. Don’t waste your money. The disease will prevail.”
Seed treatments used to be glycol based. They would penetrate the seed coat and attack the disease before it had a chance to start growing. Carriere said seed treatments worked well even if there were small skips.
However, that’s no longer the case.
“The PMRA (Pest Management Regulatory Agency) abolished glycol. Glycol is gone forever in seed treatments,” he said.
“All our new seed treatments now have to be water based. They don’t penetrate the seed coat and they don’t kick in until the disease starts to grow and it’s out on the outside of the coat. So the disease gets a good head start on the treatment.”
He said the protection products are much better, but they won’t work if there are small untreated gaps on the seed coat. Those tiny gaps are the spots where the disease will erupt, which is why Carriere thinks 99 percent is as good as no coverage.
However, there is a bright light on the scene. Applicator manufacturers are conducting intensive research and development programs to develop applicators that can meet the requirement of 100 percent coverage.
Bayer, Westfield and AGI are working on a state-of-the-art applicator that continually adjusts the treatment rate in real time according to the volume of seed flow.
Carriere said the PMRA created another problem when it changed the rules. The allowable concentration of active ingredient is now a small fraction of what it had been, making it more difficult to uniformly distribute a sufficient amount of protection product on all seed coat surfaces.
“It’s like taking a teaspoon of salt and trying to spread it uniformly over 100 kilograms of seed.”
There are two things producers can do to cope while still using an older conventional applicator.
- Slow down. The more time each seed is exposed to product, the better the chance of total coverage.
- Increase the volume of water so more liquid is available to swarm around the seeds. This dilutes the active chemical, but it also distributes it better. For more information, contact Carriere at 306-249-4484.
