REGINA Ñ A crop expert says more work needs to be done warning farmers about fan speeds on their air seeders.
“I think we’ve done a good job with pulse growers, warning them about fan speed, but we haven’t done a good job with some of these other crops,” said Brent Flaten, an agronomic crop enhancement specialist with Agricore United in Regina.
“We’ve known for a while that we have to watch the fan speeds on air seeders with flax and linola. Damaged seed can result in either dead seed or cracked seed that is more susceptible to seedling diseases.”
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The spring of 2004 was a difficult year for both flax and linola establishment because of the early seedling disease pressure.
Flaten said cracked seed leads to problems with seedling blight, pythium, rhizoctonia and fusarium, which kills seedlings.
To find out how much damage high air seeder fan speeds can do, AU conducted trials with Bourgault, testing damage as fan speeds increased. It was an update of work the company had done with the Prairie Agricultural Machinery Institute in 2000.
The first step was to refer to manufacturer specifications.
“By looking at the air seeder chart, we determined some of the fan speeds we were going to run the trials on: 2,500, 3,300, 3,800 and 4,300 rpm test speeds,” Flaten said.
“With flax or linola, we ended up putting on 41 pounds of seed per acre. That came out at about 2,500 rpm on the Bourgault air seeder, set up as a 47-foot research machine.”
A fertilizer trial applied 89 lb. of fertilizer per acre to represent 25 lb. of phosphorus and 20 lb. of nitrogen with seed, which came out to the recommended fan speed of 3,300 rpm.
To see if linola seed had any differences compared to flax, the trial used 2047 linola and Bethune flax.
“There’s not much problem at the recommended 2,500 rpm, but when you start increasing the fan speed it really increases cracking,” Flaten said. “With linola, we had close to 100 percent cracked seed at 4,300 rpm. Flax does basically the same thing.”
He said dry seed was used in the study.
“This was seed from 2003, which was a hot, dry fall, so the seed moisture was very low. The linola was less than 6.6 percent moisture and the flax was 6.8 percent. Dry seed is worse than higher moisture seed.”
With a higher moisture level in the seed, around 8.5 percent, there was less cracking than the drier seed, but still a lot of damage.
“It’s not as bad, but still, when you get up around 3,800 rpm, you’re looking at over 60 percent of that seed is cracked, and that gives an entry point for disease.”
Fertilizer effect
Flaten’s trial included a single shoot system that put fertilizer in with the seed down the same hose.
“The minimum recommended fan speed was around 3,300, so that’s where we started. There’s a reduction in cracked seed with the fertilizer. It cushions and affects the airflow, but you still have to watch out. At 3,800, you’re looking at a little over 50 percent cracked seed. Over 4,000, more than 60 percent cracked seed.”
Producers with a two-fan system on the air cart can avoid seed damage by ensuring they bump down the fan speed when they switch to flax from the higher rates of wheat and barley.
“We have a lot of issues when people don’t back off on their fan speed when going to smaller seeded crops,” he said.
“Make sure you adjust the fan speed when changing between seed and fertilizer rates. And watch your travel speed. To go an extra two miles an hour (three km-h), fan speed must be increased accordingly.”
Flaten was also concerned that as ground speed increases, so does the fan speed and therefore the amount of damage inflicted on seeds. Bourgault’s response was that the increased flow of grain and fertilizer would compensate for the higher fan speed.
“As you increase ground speed and increase fan speed, you’re also increasing the volume of grain per minute going through that hose. With that increased volume, that would increase back pressure against the fan and the actual airflow would be less than if putting on a smaller amount at that higher fan speed.”
Seed treatments
Seed treatments will cushion seed and reduce damage, but Flaten said it’s almost impossible to coat flax and linola seed with the increasingly popular water-based formulas, especially on the farm. These formulas can also be expensive.
“If you’ve got some inventory of Vitavax single, which is solvent-based, that seems to work the best. There’s still some of that out in the country. Use that first if you’re thinking of doing some seed treatment.”
He said Bayer and Bourgault did some work in 2002 with canola. It showed the same trend, with increased seed damage at higher fan speeds.
“With Foundation Lite as a seed treatment, that reduced the damage, but you still got an increase in damage at higher fan speeds.”
Flaten said the Canola Council of Canada is planning a major research project looking at different machines, fan speed and seed damage to canola. The flax council is considering piggybacking on that research, to produce more extensive results.
Check the airflow
Flaten said for crops such as pulses, producers often use a simple technique to check airflow rates.
“Pulse growers are generally more aware of cracked seed due to high fan speed issues. Farmers who grow large-seeded crops like sunflowers or peas will pull the hose off the opener at the outside edge of the air seeder, curl it up and see how much air is flowing.”
Airflow that pops up seed three metres is more than enough to move product through the hose.
“If you have it so (the seed) just pops out of the hose when it’s pointed up, you should have enough airflow to keep it moving through the system. That doesn’t guarantee you wouldn’t have a plug up in muddy soils. But at least you have enough airflow there to move the product and not settle out in the lines as it goes through.
“That’s a recommendation that people seeding larger seed have come up with. To me, it makes sense to do the same thing with a linola or flax. It’s just another ground truthing of the minimum airflow that you need to carry that product through the system.”
