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Scott and Noel Rahn, Bingham Lake, Minn., have planted corn in 22-in. rows for 13 years. The corn and soybean growers say narrow rows capitalize on the northern Corn Belt’s long days, shade out weeds faster and make the most of today’s advanced corn genetics. Narrow rows also give them better control of in-row seed spacing, they say.
Before he plants a single seed, Scott Rahn plans a foundation for top corn yields. He and brother Noel focus on field-by-field hybrid selection, crop rotation and seedbed preparation in their fields near Bingham Lake, in south-central Minnesota.
“Few management decisions are as important to high-yielding corn as those concerning planting,”says Jeff Coulter, University of Minnesota Extension corn agronomist. Of all the corn-planting decisions farmers make, hybrid selection has the greatest impact on yields, followed by rotation and uniform emergence.
These three variables account for up to 90% of corn yield increases, he says.
#1 Yield booster: Select optimum hybrids
Potential yield increase = 37-64%
Yield differences among hybrids are huge. In University of Minnesota corn trials, the gap between the highest- and lowest-yielding entries is usually about 50%, or roughly 70 bu./acre. In Iowa, that spread is around 60 bu./acre and in Ohio, about 40.
“There’s no other agronomy practice that affects yield as much as hybrid selection,”Coulter says.
Mike Zwingman, agronomy research leader for United Farmers Cooperative, York, Neb., agrees. “Correct hybrid placement is about as important as weather for good yields.”And corn genetics are advancing so rapidly that the lifespan of most hybrids is only three or four years, says Kelli Bassett, a Pioneer field agronomist from Greenville, Ill. “So you really have to be on your game.”
The Rahns take these steps to choose their hybrids:
Match hybrids to fields. Most years, they plant about eight different hybrids –each for a specific field. Working with agronomist Mark Hockel, Eagle Ag, Windom, Minn., they consider field drainage, soil properties, herbicide and fertility programs, previous crop, anticipated pest and disease pressures, scheduled field harvest –even where harvested grain will be stored.
Hockel sorts through hybrid trials from seed companies and third parties, identifying numbers that yielded well across a range of environments. Then he and the Rahns match plant genetics to field agronomics.
“We used to talk about ‘go anywhere’hybrids,”Zwingman says. But the “one-hybrid-fits-all"mentality is gone. Every hybrid has specific strengths and weaknesses, and we have to pay attention to where we place it.”
Prioritize traits. Along with corn rootworm traits, the Rahns’top priorities are early seedling vigor, standability and good drydown. Because they plant corn in 22-in. rows, they look for hybrids of medium height with an upright leaf, which intercepts more light.Recently, they started taking into account each field’s wind exposure. “We’ve had so many more wind events,”Hockel says. “Now, we identify fields that can better handle wind when we select hybrids.”
Consider storage and drying. When selecting hybrid maturity groups, it’s important to balance yield potential and drydown, Hockel says. On average, grain moisture at harvest increases by 0.25-0.44% with each one-day increase in relative maturity, according to University of Minnesota trials.
The Rahns plant 92-107-day corn. “We have multiple bin sites, with and without grain dryers. We place hybrids based on which storage site they are going to.”Later maturities are placed in fields headed to sites with dryers.
Zwingman, the Nebraska agronomist, suggests planting your shortest relative maturity hybrids first and longer-season hybrids later to spread out the pollination window and hedge weather risk.
Rotate for resistance. Western corn rootworms in some continuous corn fields in southern Minnesota have overcome the Bt-RW proteinCry3Bb1, one of the main sources of corn rootworm protection. Cry3Bb1 still works on the Rahns’farm, but they rotate Bt-RW traits to preserve its effectiveness.