Heading for 300-bushel corn yields?
By LARRY KERSHNER
Farm News news editor
FORT DODGE – If hybrid genetics was the sole answer to reaching a 300 bushel per acre corn yield, growers would have been meeting that level for at least the past decade.
That assessment came Dec. 1 from Dr. Kendall Lamkey, chairman of the Iowa State University agronomy department, speaking to an audience of 40 at the Farm News’ Ag Show.
Lamkey, who is also a corn breeder for Monsanto, said corn genetics have had the capability of of 300 bushels for more than10 years, yet few growers have ever reached that mark.
He was speaking on the prospects and challenges of reaching 300 bushel per acre yield.
Growing crops, Lamkey said, “is a complex biological process. There are just too many in-field factors that will keep Iowa from reaching 300, even though the genetics can handle it.”
In fact, he said, that some analysts think Iowa’s state average corn yield will never rise above 220 bpa.
“The best way to get the state’s average up is to take marginal land out of production, he said. Speaking to the reverse, he noted, the best way to bring the state’s average down is to plant more acres.
“Primarily, water is the limiting factor in Iowa yields,” Lamkey said. He showed Webster County yield averages for the 2004 growing season at 192 bpa, while in 2011, the average county yield was tallied at 171. “So what happened? The genetics didn’t go backward from 2004 to 2011.”
He said 2004 was a longer growing season, with average rainfall, where 2011 was a shorter season, due to rapid growing degree unit accumulation in August, along with little or no rain the entire month.
The fast gain in GDUs shortened the season by three weeks, he said. And the dry weather caused ear tip back and weakened stalks, leading to severe lodging in some areas.
He said in Webster County’s two most recent poor yielding seasons – 1988 and 2011 – there were shortened growing seasons, due to rapid GDU accumulation, below-average rainfall and heat stresses. In the two record yielding seasons – 2004 and 2009 – Lamkey said there were below-average GDU accumulations, above-average rainfall and low heat stress.
To reach 200 bpa, corn needs 20 inches of rain. To get to 300 bpa, another seven inches is required.
Lamkey said other in-field factors include:
- Soil erosion: The thinner the topsoil, the less nutrients are available to the plants.
- Organic matter: The more plant material that remains in the soil, the better moisture retention it has, and the more nitrogen from residue breakdown is retained in the soil profile.
“In short rain years,” Lamkey said, fields lacking organic matter will see “yields fall there first.”
- N,P,K: To reach 300 bpa, more pounds of nitrogen, phosphorus and potassium will be required.
To reach 200 bpa, corn needs 200 pounds of nitrogen and 300 pounds for 300 bpa; for phosphorus it requires 36 pounds for 200 bpa and 54 pounds for 300 bpa; and in potassium, corn needs 136 pounds for 200 bpa and 204 pounds for 3900 bpa.
“Water and nitrogen are the two key requirements,” Lamkey said. Growers have have to have both.
“Asking how to get to 300 is the wrong conversation, “Lamkey said. “You should be talking about how each of your fields can reach their full potential.”
Ron Egertsen, of Laurens, agreed with Lamkey’s conclusion. Egertsen said more micromanaging of acres is what will be needed for maximum profitability as land values rise.
“You know, I’m not sure we want to go there,” Egertsen said about yielding 300 bpa. “Our last 10 percent of yield is our most expensive.
“And that last 10 percent is what drives the price down 40 cents.”
Contact Larry Kershner at (515) 573-2141, Ext. 453 or firstname.lastname@example.org.
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