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upclose view of hydraulic cylinder on corn planter
UNIFORM EMERGENCE: Bill Lehmkuhl says uniform emergence is a key to high corn yield. Applying the right amount of downforce, such as with an independent hydraulic cylinder per row, is important.

Corn yield pyramid builds on uniform emergence

This farmer and consultant believes uniform emergence is the basic building block to achieving top yields.

Maybe you’ve seen what some agronomists call a yield pyramid. It includes key factors for yield, with the most important one filling the longest box at the base and building to a shorter box at the top of the pyramid.

“If we’re building that yield pyramid today, I believe we put emergence in the longest, supporting box at the bottom,” says Bill Lehmkuhl, a Minster, Ohio, farmer and consultant. He operates Precision Agri Services Inc.

Other important keys to setting the table for good corn stands include singulation, spacing and plant population. “Uniform emergence is where we must start,” he emphasizes. “The goal should be uniform emergence of the entire field within 24 to 36 hours. Otherwise, you wind up with plants which either produce only a half-size ear or no ear. If a corn plant doesn’t produce an ear, it’s a weed.”

Downforce matters

The correct amount of downforce on planter units is critical to uniform emergence, Lehmkuhl says. “With adequate, uniform down pressure on row units, you get uniform depth, and if you have uniform depth, seeds should be in uniform moisture conditions,” he explains.

“Uniform moisture should result in seeds germinating at about the same time,” he continues. “If they germinate within a few hours of each other, you will get uniform emergence. It all starts with downforce.”

Enough downforce to ensure uniform depth in moisture without so much pressure that you create soil compaction means finding the happy medium, he says. That’s why there is currently a large amount of interest in systems that adjust downforce row by row. Precision Planting introduced DeltaForce to accomplish this hydraulically a few years ago. Some planter manufacturers use the Precision Planting system, while others use their own version of a hydraulic solution to control downforce independently on each planter unit.

“It’s critical to get it right and not create sidewall compaction,” Lehmkuhl says. “When the third crown root emerges from the seedling, it must get out of the trench and not be hemmed in due to soil compaction.

“If it can’t get out of the trench easily and it turns hot and dry early, plants will struggle. Too much downforce is one reason why those sidewalls may be compacted and not allow roots to penetrate easily.”

Monitor seed placement

Assuming each row is planting at the same depth because you set the controls for the same depth can be a costly mistake, Lehmkuhl says.

“We’ve even found differences in depth placement of five-eighths inch to three-quarters inch on various rows of a new planter when every row was set at the same factory setting,” he notes. “It’s even more likely as planter parts that contact the ground wear. We recommend taking time to dig in each row and check seed placement.”

The best way to know if you’re managing downforce correctly and setting the stage for good emergence is to watch the reading for ground contact displayed on many modern planters. “If you’re getting 100% ground contact on each row, you have better odds for placing seeds at the right depth,” Lehmkuhl says.

An automatic downforce control system is even more crucial for high-speed planting, he adds. “You need enough downforce on each row to maintain 100% ground contact traveling at speeds up to 10 miles per hour.”

TAGS: Planting
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