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The Do's and Don'ts of Nitrogen Management

Nitrogen management doesn’t have to be a guessing game.

Nitrogen (N) applications are vital for driving corn yields. Still, potential missteps lurk around every corner. 

That’s why Brian Reinhart, Slater, Iowa, makes his N program one of his main priorities. Reinhart’s heavy, black soils stay cold and wet in the spring, and they’ve created challenges for his previous N programs. Up until two years ago, Reinhart’s N management plan consisted of applying 100% anhydrous ammonia in either spring or fall, depending on the weather. Inconsistent yields spurred him to make his N program better fit his operation, field conditions, and goals while balancing the potential risks. 

Instead of applying N all in one shot, he now split-applies N several times during the season. He starts in the spring by applying anhydrous ammonia preplant. Then he bands 32% N at planting 4 inches off the row. He makes side-dress applications depending on hybrid needs. 

“I make sure I don’t throw money away,” says Reinhart. “My nutrient management program is based on a systems approach so I get the most efficiency out of the dollar spent.”

While every operation differs and each year brings a unique set of challenges, the tips on the following pages can deliver the biggest bang for your buck in 2017.

Do think about timing

While location and soil types may determine application timing, it’s still important to evaluate your program. Not having sufficient N at the start of the season is detrimental to corn.  

“There needs to be a certain amount of N up front to get the corn started,” says Fred Below, a University of Illinois (U of I) crop physiology professor. “If you don’t have any out there, I’m afraid that plant growth will be slow and yield potential will be lower.”

Early in the season isn’t the only time it’s crucial to have N available.  

“You want to make sure the N is available before the rapid growth stage of V8 or V10,” explains Below. “That’s when corn is going to really start taking up N. It’s fairly hard to make a corrective application after that.”

After weighing the pros and cons, Reinhart opted for spring applications, forgoing fall applications for the last two years. 

“Not only is the timing of N applications important but also the form of N is critical,” says Reinhart.  “Nitrate N is very important for helping the plant grow efficiently early in the season.”

Early or late? 

Two timing scenarios exist for N applications.

  • Early applications ensure the task is done. Unfortunately, it also exposes N to loss through leaching or denitrification.
  • Late N applications slice the risk of loss. However, the practice increases the risk of inability to get in the field, says Peter Scharf, University of Missouri (U of M) Extension nutrient management specialist.

“The most important thing is to have multiple possibilities for how farmers can get the job done,” says Scharf. “If they are starting early enough, they’ll get it done 19 out of 20 years.”

While Reinhart is able to lower his risk of loss, he has one concern about the early spring preplant application.

“The only thing that bothers me with the spring preplant application is compaction,” says Reinhart. “In my heavy soil in corn on corn, I have some compaction.” 

He has to carefully watch field conditions and stay out of wet fields to avoid creating additional compaction. 

Do Make it Multiple

For Brian Reinhart, it makes more sense to make multiple applications throughout the season instead of just one all at once. 

“I don’t want to put all my eggs in one basket like I used to,” says Reinhart. 

“Making multiple applications is a good practice to minimize N loss and to make sure the N is available when the crop needs it,” adds U of I’s Fred Below.

If you decide to split N applications, do it in a way that you aren’t creating additional work for yourself when spring rolls around. If you apply N in the fall, don’t make partial applications, says U of M’s Peter Scharf. Instead, apply full rates on a percentage of your fields. Rather than risking a full rate on every field, you then will only risk a full rate on a percentage of the fields. The remaining fields can have the full rates applied during the spring applications. 

With this method, you’re still reducing risk, and logistically you’ll be ahead come spring. Otherwise, you have to make multiple trips in every field, and your workload hasn’t benefitted by making fall applications, says Scharf. 

Don’t fix it if it’s not broken

While split applications are gaining in popularity, they may not be necessary, and they aren’t a requirement, says John Sawyer, Iowa State University (ISU) Extension soil fertility specialist.

“If you’re on soils that are not excessively well drained or have high potential for excessive wetness, then a one-time application can work,” he says. “Our current research doesn’t show that split applications always produce higher yields or have lower optimal N rates.”

Split applications are valuable for reducing the chance of N loss on coarse-texture (sandy) soils, he adds. 

Don’t underestimate Mother Nature 

“I don’t want to throw money away,” says Brian Reinhart. “The weather dictates a lot of the decisions I make.”

“You can’t outpredict Mother Nature,” says ISU’s John Sawyer. “No application timing is without potential issues.”  Sidedress applications can have risks such as the potential to be rained out of the field or for conditions to turn dry after an N application. 

U of M’s Peter Scharf’s solution to the weather involves planning. “Have a plan A, B, C, and maybe even D so you can handle different weather situations,” he says. 

Sometimes that’s knowing you can call an applicator, other times it’s getting a sprayer set up for nitrogen. If all else fails, know who you can hire to fly it on.

Don’t Forget failures

No matter your strategy, there will be years when the weather doesn’t cooperate with your plan. 

“Recognize the times when applications failed,” says U of M’s Peter Scharf. “You’re taking a gamble. You’re going to win sometimes; you’re going to lose occasionally.”

You can do everything exactly right and then get too much rain after you sidedress, and your plan goes down the drain, says Brian Reinhart. Learning from those experiences can help you better prepare for the future. The use of products like N inhibitors can help if application timing isn’t ideal, says ISU’s John Sawyer. 

“There are two general classes of nitrogen inhibitors,” says Sawyer. “One of them is a nitrification inhibitor, and it’s used to slow the conversion of ammonium to nitrate. 

“The other is a urease inhibitor, which is used to slow the conversion of urea to ammonium, which lessens the chance of volatile loss as ammonia,” explains Sawyer. “That would be helpful if urea is surface-applied – especially in high-surface residue systems like no-till.” 

Do factor in environmental concerns 

The spotlight continues to shine on high nitrate N levels in Midwestern rivers and streams. It’s important to balance the environmental side of N applications along with the other factors that contribute to the planning process. Using the wrong rate has consequences. “Getting the N rate right is not easy,” says U of I’s Fred Below. “Being low really hurts yield and having excess hurts the environment.”

These steps can help you keep it in the fields and out of rivers and streams. 

  • Make sure you need extra N before applying it. “Some producers worry about being short of N and apply extra as insurance, but it’s also an environmental concern,” says ISU’s John Sawyer. 
  • If you make fall applications, make sure it’s a recommended practice in your location. “The warmer and wetter you are, the more risk you have for N loss,” says U of M’s Peter Scharf. “How much you should limit your fall total depends on your climate.”
  • For fall applications, follow the 50°F. rule. The soils should be consistently 50°F. or cooler at the 4-inch depth before making fall applications, and the colder the better, says Sawyer. Even when you follow the 50°F. rule, you still have a medium-level risk of N loss, says Scharf.
  • Know that you can’t plan for the weather. “If you make multiple N applications, you can adjust rates for what the weather has done or has not done,” says Below. 

Do use available technology 

Digital tools are able to assess the impact of weather and the potential N loss along with N availability. These tools can track the weather, how much N was applied, and what’s still available, says U of I’s Fred Below. 

“Several universities in the north-central region provide an online tool called the Corn N Rate Calculator,” says ISU’s John Sawyer. “It provides a suggested N rate for the specific state or substate area, crop rotation, and prices of N and grain.”

It also provides a range of most profitable rates to choose from, based on a variety of producer-specific situations such as capital available for fertilizer purchase, expectation of weather for the current season, risk tolerance for yield issues if short of N, and risk tolerance for water quality, says Sawyer. In addition to online tools, there are other options to help you make in-season decisions. 

“You could use the late-spring soil nitrate test to help adjust in-season applications,” says Sawyer. “Another option is the use of corn canopy sensing to determine N stress and application need.”

If you are able to determine that the corn is short of N, an application at any time is better than none at all, says Below. “Rescue applications can be very effective if the N has been lost,” he says. 

Y-Drop technology is another area that Brian Reinhart has invested in for in-season applications. “Y-Drop technology allows the placement of the N right by the row so it’s rapidly and freely available right where the roots are,” says Below. 

Another rescue treatment option is to fly it on, he says. While not the most inexpensive option, Below has seen it utilized during wet years when applicators aren’t able to get in to the field to sidedress. 

Don’t forget to calculate the economics 

The change in Brian Reinhart’s N program isn’t saving him much money yet, but he’s made sure it isn’t costing him either. The switch allows him to cut a few N rates, which he uses to pay for the different forms of N he now uses. Over time, his soil nutrient levels will come into balance, he believes, and he’ll be able to continually improve the efficiency of his applied N. 

“There are several yield-based and economic programs to help you decide the rate,” says U of I’s Fred Below. “They take the yield history, price of the grain, and the cost of N.”

The results help you calculate the maximum economic return of the N, says Below. Another factor to remember is that purchasing in the fall tends to be cheaper, adds Below. In general, there’s less for the retailer to do in the fall, but you can also prebuy N in the fall if the price is right. 

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