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About 20% of growers across the country are using variable-rate seeding, and that number continues to go up, says DuPont Pioneer’s Steve Butzen. “If you already have the equipment, know your field’s management zones and understand how your hybrids will perform under different yield conditions, VR seeding is almost certain to be cost-effective.”
Across 20 University of Illinois trials under dry conditions in recent years, yield leveled off at only about 32,000 plants per acre. Under lower-yielding conditions, responses to population tended to flatten out at populations in the high 20,000s or low 30,000s. Under higher-yielding conditions, there were some responses up to the low 40,000s.
Variable-rate seeding: Make plant populations pay
With the right tools, growers can tailor plant populations to the varying growing environments within a single field. Knowing if, where and by how much you should change rates can make variable-rate (VR) seeding challenging. And the jury is still out on whether or not it pays.
“If your field has some sand pockets among deep black soils, it only makes sense that planting different populations across that field can pay off,” says Syngenta’s Chris Cook. “However, it’s critical to calibrate your planter correctly for the hybrid you have and to select the right hybrid to maximize the populations you’re planting. It’s a balancing act.”
“Variable-rate seeding is not a bad idea, but it’s not going to be incredibly profitable if you are already managing populations correctly for a field,” adds University of Illinois’ Agronomist Emerson Nafziger.
Southern Illinois grower Matt Bowlby, however, believes he has seen significant results. The fifth-generation row-crop grower who considers himself a “number cruncher” has been collecting data on his fields for nearly a decade and has been variable-rate seeding all his corn acres for 3 years. His rates vary from 28,000 to 36,000 seeds per acre across the fields due to a wide variance in soil types.
“We always felt like we were leaving yield behind, so we traded planters for one with variable-rate seeding capability,” Bowlby says. “We’re trying to maximize the yield potential of different soil types and field conditions.”
A couple years ago, Bowlby received the prescription maps from his consultant and something about them just didn’t seem right, so he switched off the VRS. However, the yield map clearly showed where he should have been planting at a lower population in the middle of the field. “I’d calculate that we lost about $75 an acre in that area by seeding too high,” he says.