Ken Ferrie: Using Urea for N or Going Corn-on-Corn in 2023? Read this First

As farmers look to establish their 2023 cropping plan, some are looking at changing their rotation. Ken Ferrie, Farm Journal Field Agronomist, says he has been fielding questions on the subject.

“For some growers, their local markets are driving their decision to consider growing more corn-on-corn or beans-on-beans,” he says. “In some cases, farmers are driven by strong yields they saw this past season.”

Before you make a crop rotation change, Ferrie says consider the potential ramifications. 

“When we grow the same crop back-to-back, it puts pressure on the system,” he explains.

Ferrie addresses some of the questions farmers are asking in this week’s Boots In The Field podcast. 

Here’s a summary of what he shares.

1.    The first question Ferrie always asks a farmer wanting to go with a mono-crop: What are you expecting for yield with this crop rotation change? 

“When we grow the same crop back-to-back, we have to be realistic,” he says. “For growing corn-on-corn, we plug in a 10- to 15-bushel drop in yield. For beans-on-beans the drop is typically 5 to 7 bushels per acre. 

“I know in some years that doesn't happen. But in other years, the loss is more than that. Corn-on-corn in dry years can dip 30 to 40 bushels per acre, like some people experienced this year,” he adds.

2.    If the numbers you pencil out still fit with realistic yield goals, then the question is: How much experience do you have with a mono-crop system?

Ferrie says going with beans-on-beans is by far the easiest. Corn-on-corn is another matter and requires more management and awareness of what could go wrong. 

“Growers who have a lot of corn-on-corn experience have learned by the school of hard knocks on what works and what doesn't,” he notes. “These growers don't need much coaching. But growers new to the concept need more counseling to keep the learning curve from getting too steep and too expensive.”

Farmers going with corn-on-corn must give thought to the carbon penalty – the tie up of microbes and soil nutrients. 

“This is best accomplished by managing the 4Rs of your fertility program, which usually means some fertility banded near the row with the planter or the strip-till toolbar,” he says. “Managing residue at the furrow has got to happen, which involves planter setup.” 

Some additional considerations include:

Managing insects like rootworm, which involves hybrid selection and using planter-applied insecticide. 

Disease pressure intensifies in corn-on-corn and must be managed with hybrid selection and fungicide applications. 

Differences between hybrids play a role as some just don’t tolerate corn-on-corn stress very well. 

“In our plots in 2022, comparing two hybrids in corn-on-corn and corn-on-soybeans… with our dry August, one hybrid had a 5-bushel hit to corn-on-corn. The other one had almost a 40-bushel hit to corn-on-corn. The higher yielding hybrid in the rotated corn was not the higher yielding hybrid in the corn-on-corn plot. Hybrid selection matters,” Ferrie says.

Consider harvest and planting practices and what the impact would be to both if you switch all your acres to corn. Can you get everything planted and harvested in a timely manner?

3.    If you consider all these factors, and you are still planning to go with a mono-crop system, have you thought about your marketing plan?

Ferrie says sometimes growers are watching their neighbor and want to duplicate their process. His advice is to spend some time learning about the details that your neighbor is using. 

“I would also recommend finding out what the yield level is for your neighbor. What is your neighbor considering as success? His level of success may not meet your expectations,” Ferrie says.

“By taking time to walk through these scenarios with growers, we can sometimes stop a train wreck before it happens or at least get the grower to step off the tracks before the train runs through.”

4.    Can you use urea as an N source—replace some of the spring N in corn? 

Ferrie says this is a question he has been fielding frequently in central Illinois as some farmers are finding inexpensive urea.  

“The short answer is yes – especially on wheat acres. Many farmers in areas of the United States and in some countries around the world use mainly urea as their N source,” he notes. “You do need to know the weakness of this product so you can farm around it.”

The risk with urea is volatility. “It would need a urease inhibitor,” he says. “A urease inhibitor will buy you some time after application to get it moved into the ground.”

Applying urea to bean stubble for next year's corn crop gets a little riskier than its use on wheat ground. 

“You still need a urease inhibitor to slow or stop volatility. Be aware that applying urea to frozen ground puts you at risk of runoff if a rain event occurs. That risk goes down if you have a cover crop growing,” Ferrie says.

“If your present plan is weed and feed, where you blend your herbicide with your 28% and 32% and make it one pass, be aware that with urea, you're most likely going to have to make two passes -- or get your retailer to impregnate that urea with the herbicide,” he says.

Many retailers don't want to do this because of fear of contamination at the blender. 

“We go on urea spread complaint calls almost every year,” Ferrie says. “You have to calibrate your spread width and your spinner speeds to get uniform spread of urea.” 

He cautions that a truck calibrated for MAP and potash is not calibrated for urea use. Poor calibration will lead to “waves” in the corn later. 

Keep in mind, that urea’s first conversion is to ammonium, which the corn plant can use (The corn plant can use both ammonium and nitrate.). 

“Ammonium is like jet fuel to soil microbes,” Ferrie says. “I've seen in our plots where the carbon tie up from the microbes will immobilize 150 pounds of urea, especially in corn-on-corn. It just disappears from the balance sheet.”

He explains it's just immobilized and will mineralize back into the system later. But your corn can experience some N deficiencies waiting for that to occur. 

“Now the same thing happens with your 28% and your 32%, but one-fourth of that product is nitrate, which the microbes don't snatch up as fast, and it usually keeps the corn plant happy until this mineralization takes place,” he says. 

The temporary slowdown in corn can be avoided with some planter-applied N. 

“I think there are places where (the use of urea) will help cut your N cost. So I am not against it. I just want everybody to understand there's some extra loops you got to jump through if you're not used to it,” he says. 

Learn more in the podcast, here:

Learn more about Ferrie's Beyond the Basics agronomic series, available online from Crop-Tech Consulting. If you provide Crop-Tech Consulting with your CCA information, you can get CCA credits.

Crop-Tech Consulting will host their annual virtual Corn College on Jan. 5.