Coulter drills are known for precisely placing seed and fertilizer, but they are also known for their difficulty in heavy stubble, heavy clay soil and uneven ground.
To answer these concerns, Bourgault Industries of St. Brieux, Sask., set out to build a better air coulter.
Robert Fagnou of Bourgault said designers worked to take the best aspects of the company’s parallel link hoe drill and develop them for a coulter machine, the 3710.
Hoe drills on parallel arms are able to follow the soil and avoid trash buildup. Coulters are highly accurate and capable of low soil disturbance because they cut through the soil rather than tear.
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A coulter’s ability to follow the ground without being lifted out of the seed bed by the packing wheel was critical to ensuring precise seed placement.
“Previous machines, like the (Bourgault) 5725, set the seed depth at the frame. This one sets it individually at the opener,” said Scot Jagow, the Bourgault engineer who applied for the patent on the design of the parallel walking coulter arm.
“We had heard from farmers in the northern U.S. states that they wanted a coulter design that wouldn’t ride up on corn or sunflower stalks. Some designs rely on gauge wheels to set the depth, but these are prone to interference from uneven soils and heavy stubble.”
Independent operation
The new Bourgault model’s contour parallel link system uses a walking axle between the cleaner and packer wheels, which allows the seed and fertilizer opener to operate semi-independently and remain at a near constant depth in the seed bed zone.
“It is a fairly simple design, and it allows us to build wider machines and have them maintain that individual seed depth with low disturbance across a unit that can be 60 feet wide,” Jagow said.
“We looked at single (trailing) arm designs, but they will change the angle that the (seed tool) enters the soil depending on their relationship to the frame. So your depth of travel is lost if you want precise seed placement. So it had to be a parallel arm …. This way we get 16 inches of travel on an individual opener, nine up, seven down.”
Pressure is supplied to each seeding unit through a hydraulic cylinder and is adjustable from the tractor’s cab. The walking axle can place 70 to 200 pounds of down force on the packer and cleaner wheels. The opener can get 450 lb. of force.
“If you really need a lot of down force on the opener, the packers can be locked up for things like pea or lentil stubble,” he said.
Packers are adjustable in quarter inch increments and are available in shouldered, round or V-shaped designs.
Fagnou said all implement makers have improved their coulters when it comes to hair-pinning of stubble since the introduction of the original Barton-type units that used a single following arm and coulter.
“We’ve really gotten away from hair-pinning with the 20 inch coulter and an anti-hairpinning scraper,” he said.
“If you want to boost the amount of starter fertilizer, the scraper allows you to add a band of fertilizer beside the seed row as well. It can also be used for seed if increasing your (seed bed use) is something you want or need,” Fagnou said.
The scraper can deliver up to 20 percent seed bed use on a 12-inch spacing.
Jagow said the scraper has been tested in heavy clay soil and gumbo in Manitoba’s Red River Valley and in Montana without serious plugging problems.
“For really low disturbance, if heavy (crop) residues aren’t a big issue, then you can go to our other scraper. In dry conditions where you want that seed bed closed up tight without much soil disturbance, that is the way to go,” he said about the scraper, which is based on the Barton design.
“We had seven prototypes out there in Saskatchewan and in North and South Dakota in 2007 and 2008 before releasing it this summer.”
Every second row of the 3710 can be locked up for 15, 20 or 24 inch rows to meet the needs of soybean growers or those wanting to work with wide row spacings.
For the 2010 season, the 3710 will be available in 40, 50 and 60 foot units. Spacings of 7.5, 10 and 12 inches can be ordered and the company’s mid-row banding system can be added for single pass placement of all seed and fertilizer.
