Tim Hartsock tosses a Hula-Hoop across his newly emerged soybeans to measure stands. By counting plants and adjusting seeding rates, he's improving stands and cutting costs.
“We're trying to learn what population to use,” says Hartsock, who operates Hartsock Ag, Chillicothe, OH, with his brother Tom.
Being a bean counter can pay off, says Ed Lentz, Ohio State University extension agronomist.
“Seed costs have basically doubled,” says Lentz. “Bin-run soybeans cost about $10-12 a unit. And now Roundup Ready varieties cost $20-24 a bag.”
So if you reduce seeding rates by 50,000 seeds/acre, you can save $6-9/acre, Lentz points out.
Hartsock started tossing the Hula-Hoop around in his fields four years ago, when he began growing Roundup Ready soybeans. He drills 2,000 acres of no-till soybeans in 7½" rows, taking stand counts shortly after the crop emerges.
“You need to make sure all the soybeans are up, especially in no-till where they don't emerge at the same time,” he says.
He has tried rates ranging from 185,000 to 240,000 seeds/acre. Now he varies rates based on soil type. On poorer soils and clay knobs, he plants 220,000 seeds/acre. On darker, higher-producing soils, the seeding rate is 175,000. The final stands on both types of soil range from 100,000 to 175,000 plants/acre.
Hartsock varies rates manually using a Rawson Hydraulic Drive. The rates are logged using an Ag Leader PF 3000 computer and mapped using Agris AgLink Professional software.
Although the Ohio Agronomy Guide suggests 175,000 seeds an acre, many producers plant nearly 250,000, says Lentz.
In 1999, Ohio agronomists set out to find the optimum seeding rates for drilled soybeans. The results showed there was no advantage in planting more than 200,000 seeds/acre. Yields differed less than 1.5 bu/acre among the various seeding rates.
Lentz found similar results last year. A harvest population of 140,000-160,000 plants/acre often provides optimal yield, he says.
As seeding rates decrease, Lentz says calibration becomes more crucial. If you're calibrating drills for lower settings, don't rely on the planter or drill book settings. “Seed sizes vary from year to year. This year some lots have a germination of 70% — so you'll definitely need to adjust seeding rates,” Lentz stresses.
To count plants using a Hula-Hoop, randomly toss the hoop and count plants inside the circle, says Troy Putnam, Pioneer area agronomist at Hillsboro, OH. Convert plants per hoop to plants per acre by multiplying the number of plants by the appropriate factor.
“I prefer to use a 28" hoop for ease of calculation,” says Putnam. With a multiplication factor for that size at 10,000, 19 plants × 10,000 = 190,000 population.
For a 26" hoop, multiply the number of beans by 11,800; for 30", by 8,900; 32", 7,800; 34", 6,900; 36", 6,200; and 38", 5,500. If you don't have a Hula-Hoop, use an 89"-long wire or sprayer tubing to form a 28" inside-diameter circle.