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Corn+Soybean Digest

Tips for More Accurate Planting Tools and Practices

Aldean Luthi is planting corn on a cool May morning in west-central Minnesota. In the cab of his John Deere tractor, pulling a JD1780 planter, he scans three separate monitors. On one screen, he checks his variable-rate seeding map. On another, he tracks row shutoffs. And on the third screen, he watches how well the planter itself is doing all its jobs.

Luthi is a planting perfectionist. He uses two new aftermarket tools from Tremont, IL-based Precision Planting to improve his planting accuracy: 20/20 Seed Sense and 20/20 AirForce.

The 20/20 Seed Sense system measures key planter functions and flags problems row by row. The GPS-linked tool displays vacuum pressure, population and singulation. Skips and doubles show up on the monitor as they happen. Ground contact and good ride readouts tell Luthi when he needs to adjust his speed. SeedSense also measures down pressure, showing Luthi how much weight he can remove from the depth gauge wheels and still maintain uniform seeding depth.

“Yield is in the details,” says Luthi, who raises corn and soybeans on 1,700 acres in Stevens County, MN. Knowing when the planter isn't doing a task correctly “gives you the ability to make adjustments as you are planting, rather than waiting until the corn comes up to see how you did.”

In 2009, Luthi added Precision Planting's 20/20 AirForce, which automatically adjusts planter down force for changing seedbed conditions and seed box weight.

Luthi, who has about 70% of his operation in continuous corn, feels that more consistent down force control “was a real advantage” last spring. He deals with heavy residue; his soils were cold “and there were no forgiving rains after planting in our area. Just a quarter-inch difference in planting depth made a difference because seeds were lying in dry soil for so long.”

BILL LEHMKUHL, a farmer and consultant with Precision Agri Services, Minster, OH, troubleshoots planting problems. “Out of all the planter adjustments, down force is one of the most critical,” he says, “and one that is often ignored.”

Too much contact force on the planter's depth gauge wheels over-compacts the soil around the seed, causing uneven emergence and “hatchet” or “Mohawk” roots, he says. Too little down force and seed placement suffers. Yet, Lehmkuhl has seen many planters where the down-force springs were set when the implement was delivered “and never changed again.”

Recent research confirms that planter down pressure affects seed depth and corn emergence rates, says Mark Hanna, Iowa State University Extension agricultural engineer.

Hanna's 2005 replicated study looked at how down pressure alters the environment for corn plant germination and early growth. He tested three levels of down force — 40-110 lbs., 110-200 lbs. and over 200 lbs. — in dry, moist and wet soils with no tillage. The trials also included a randomly variable contact load similar to that of a conventional planter, as a control.

In moist or wet soil, “corn emerged more rapidly with a low load,” Hanna reports. But in dry soil, corn emerged faster with a heavy load. In the control treatment, where down force was randomly variable, corn “did not emerge as rapidly as the optimal loading for a given soil condition.” Even though the planter depth settings were the same, seeds were planted nearly half an inch deeper when the load was heavier, Hanna says.

The research shows the importance of “carefully adjusting down pressure on depth gauge wheels,” Hanna says. “Pay attention to soil conditions and lighten up when it's wet or moist. Apply more contact pressure in dry conditions.”

The 20/20 AirForce system makes it easier to maintain the correct down force, says Lehmkuhl, who raises no-till corn, beans and wheat. He used the technology in 2009. “It's definitely a useful tool,” he says.

AN AIR COMPRESSOR and uplift bag increase or decrease the down pressure exerted by the planter's springs or pneumatic cylinders. The operator enters the settings, and the tool adjusts the air pressure to press or lift in order to maintain constant down force, regardless of the soil conditions. “I'm surprised at the amount of change you see going through the field in soil conditions and soil type,” Lehmkuhl says.

Adjusting down force “on-the-go is an excellent concept,” Hanna says. However, optimum down force “can change pretty quickly — sometimes over distances of just 3-6 ft.,” his research shows.

The AirForce system can't fine-tune down force over that short a distance, Luthi says, nor can it vary the down force by row unit. “But it will adjust for changes in soil type, terrain or moisture within about 100 ft. or so,” he says.

In one field last spring, for example, the monitor alerted him to an area of peat soil that was much softer than the clay loam soils around it. Luthi immediately decreased the pressure in that part of the field. Before he got the SeedSense monitor, Luthi almost never changed planter down force within a field. He'd set the down-pressure springs when he pulled into a new field and hope for the best. “We tended to go on the heavy side to make sure we had good penetration. I know we were overdoing it when the seed boxes were full.”

Lehmkuhl agrees that “there's a tendency to run too much down force.” He often sees newly planted fields with a wave-like footprint caused by excessive down force.

It's helpful to get real-time feedback on other planter functions, too, Luthi says. For example, a “red” readout on three rows led him to discover a loose chain. The chattering chain affected spacing but not population, so the malfunction didn't show up on the population monitor.

SeedSense also showed Luthi when he could plant faster without sacrificing accuracy. “The monitor will tell you where your smooth ride is. If you lose your good ride and good spacing, one way to correct that is to slow down. But if everything is ‘green,’ you can plant faster, and we did — up to 7.5 mph — knowing that conditions were good and we could keep the seeding depth and spacing uniform.”

Luthi has used Precision Planting technology for two seasons and liked it so well he became a local dealer. His son and son-in-law, who farm with him, install the equipment during the winter. The systems cost between $4,000 and $6,000 each, depending on planter make and model, and fit most major brands.


Corn growers aspire to a “picket fence” stand. But does greater planting accuracy actually translate into higher yields and more profit?

Results from extensive research on the effects of uniform spacing on corn yields has been variable, says Joe Lauer, University of Wisconsin Extension corn agronomist. A few states have shown a yield advantage for reducing spacing variability. Yet, studies in Illinois, Iowa, Wisconsin and Minnesota have found no yield gains from precise plant spacing at today's corn plant populations, Lauer says.

At 30,000 plants/acre, the average space between plants is less than 7 in. “As population goes up from there, plants are getting closer together and variation becomes less significant,” Lauer says. In fact, if you're achieving the recommended plant population, the difference between sloppy and perfectly precise is pretty small, he says. “There's not room to even get much spacing variation.”

Jeff Coulter, University of Minnesota Extension corn agronomist, agrees: “Advantages to precise spacing of seeds are relatively small, as long as you don't have many doubles or skips.”

But Hancock, MN, farmer Aldean Luthi feels that precise spacing pays off: “Any seedling competition caused by plants closer then 4 in. will result in those corn plants putting on a smaller ear.”

Bill Lehmkuhl, a farmer and planter expert with Precision Agri Services of Minster, OH, also says accurate spacing matters. “Yield is not in plant population - it's in ear count. Picture-perfect, carbon-copy ears cannot be attained by sloppy spacing.”

By contrast, everyone agrees that uniform seed depth is important because that influences emergence timing.

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