Big force, delicate balance, 5-bu. benefit

SureForce hydraulics balance 1,000 pounds down force with 350 pounds uplift and leaves seed just right

Hydraulic depth control has been available on planters for a decade, but they’re seldom installed, despite the fact that field trials give hydraulics a five-bushel benefit over spring-type down force.

In a recent side-by-side trial in Iowa, a dozen strips planted with an Ag Leader SureForce hydraulic system averaged 5.128 bu. better than the adjacent dozen strips planted with spring-type down force. The left half of the planter was equipped with the original factory down-force springs while the right half was equipped with SureForce, which was introduced by Ag Leader two years ago.

The field trial information was presented Dec. 1 in a webinar organized by No-Till Farmer Magazine.

Ag Leader technology specialist Brett Buehler explained the functions and advantages of hydraulic down force working in conjunction with hydraulic uplift.

In the Ag Leader system, both down force and uplift respond instantly to signals from a sensor installed on each row unit, Buehler said in a phone interview following the workshop.

It’s called a weed the moment one plant lags behind the norm, it starts robbing the main herd of moisture and nutrients. Thus the straggler on the right is a weed and not crop. | Brett Buehler photo

“The sensor knows how much weight is carried by the gauge wheels on that row unit,” said Buehler, adding that the known weight factors include the row unit itself, seed and insecticide.

Buehler said opening discs have to penetrate the soil. Coulters and row cleaners and closing wheels all create uplift on the row unit, as if the soil is pushing up against the opening disc.

“What you have is two opposing forces fighting each other. You have all the weight of the row unit assembly pushing down into the soil. And you have the force of the soil pushing up against the row unit. Our goal is to maintain just the right amount of weight on the gauge wheel to create the ideal trench.

“There’s a popular misconception about weight on the row unit. Most guys say they want only the minimal amount of weight to put the openers at the right depth with the least amount of gauge wheel.

“But without enough gauge wheel load, the trench walls collapse behind the opening disc. You’ll have dry soil and residue dropping into the trench and then you have emergence problems. You want enough load on the gauge wheels so the walls are stable and the trench remains open until the closing wheels close it. But too much gauge wheel load can collapse the trench.”

The SureForce hydraulic control system delicately balances 1,000 pounds down force with 350 pounds uplift to maintain just the precisely correct amount of pressure on the opener. | Brett Beuhler photo

He said SureForce targets 100 pounds of gauge wheel pressure by default. But in a dry planting system like the mid-west experience this past spring, most of his customers had to run up to 200 lb. to create a proper trench with firm sidewalls. SureForce uses a gauge wheel on each side of the opener to create compaction on each side, thus preventing the walls from crumbling down into the trench. Buehler said a clean trench is critical to correct seed placement.

“The goal is to get all the seeds down to the moisture level at two inches or slightly deeper. We want every seed to access moisture at the same time so they all germinate and emerge at the same time. Every plant that comes out of the ground before the others will put the neighbouring corn plants at a disadvantage all season. Conversely, the slow-emerging plants will be a drag on neighbouring plants all season. They now become weeds.”

Buehler said farmers are beginning to understand the concept of the ideal seed trench, how it should look and how to adjust down force to achieve that firm sidewall. He added that uplift is a more difficult concept to explain to people who still use factory standard spring force.

“We have a dual-acting hydraulic cylinder on each unit. We use tractor hydraulic pressure on the uplift side. There’s a pretty large ram coming out of the cylinder to deal with 2500 psi from the tractor. But the surface area in there is so small that it only generates 350 lb. uplift.

“On the down-force side we can apply about 1,000 lb. We take 1,000 lb. down force minus 350 lb. uplift and we end up with a net of 650 lb. down force. So we’re creating a constantly variable balance on each row unit.

“The system we introduced back in 2012 was a two-channel system that didn’t have uplift. Ag Leader was the first company to have active hydraulics on row units. But we saw that in conventional till, we didn’t need hydraulic down force, so we came out with some springs that were like down-force springs, only we made them apply about 150 lb. constant uplift. Our hydraulic down-force cylinder overcame that, so we created a system where the two were balancing.”

He said the fine balance between uplift and down force is the critical task of the sensor. This balance is so precise that, even dealing with these high pressures, each row unit only requires 0.25 gallons per minute. A 16-row planter needs four g.p.m. Minimum pressure is 2,200 lb. per sq. inch. The system does not use an accumulator.

About seven years ago, Ag Leader saw that some farmers need 500 or 600 lb. of down force. That’s when engineers turned their attention to developing the SureForce, which has more down pressure plus hydraulic uplift. This eliminated what he calls the clunky slow-responding springs.

Buehler said airbags don’t like hydraulics. While it may seem that active air bags can respond as quickly, Buehler said they have only two channels fed by quarter-inch lines.

As hard as the compressor works to increase pressure, it cannot keep the air cylinder pumped up enough to satisfy the needs of all the bags.

Likewise, when bag pressure needs to drop, it again takes too much time.

Red lines indicate where the AgLeader put down pressure greater than 300 pounds. The diagonal red line across the top right of the map made no sense at all, until the farmer realized this was the route his neighbor used during previous winter hauling firewood with his ATV. | Ag Leader photo

Maintenance is the other factor. Keeping all those bags at the correct pressure means the compressor is running almost constantly.

Buehler said SureForce shines when planting into no-till land on side slopes. This scenario plays havoc with the concept of precision planted rows. Gravity naturally pulls the planter down, which is expected. The real problem arises when the openers are pulled into the previous year’s seed rows or into thick cover crop or out of the strip-till path.

With SureForce, the sensors instantly feel the change in conditions and they trigger higher down force. As the planter drifts further off course, the sensor continues to order up more psi to deal with the issue.

He says Ag Leader had considered adapting the SureForce technology to air drills, but the project was dropped because of cost and the feeling that small grain seeding equipment didn’t really need the precision that corn planters need.

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