Nitrogen placement is more complicated than just putting down 200 pounds each year because that’s what you’ve always done. It takes research, timing and dedicated planning to maximize your efficiency and yield each season. Missy Bauer, Farm Journal Associate Field Agronomist teaches nitrogen placement, timing and how planning can lead to better nitrogen utilization.
When you apply nitrogen it feeds more than just the crop. “Microbes must break down previous crop’s residue,” Bauer says. “In order to do so they must have an energy source [nitrogen].”
Plan ahead and keep the microbes happy so residue will be broken down quickly and nitrogen can be used in the plant. Warm soils help speed up the break down and nitrogen feeds the microbes to help them do their jobs. The type of residue the microbes need to break down makes a big difference in rates needed. Soybeans are 30/1, corn 60/1 and wheat is 100/1 carbon to nitrogen ratios to.
“Some call soybean residue a nitrogen credit, I don’t think of it that way,” Bauer explains. “I call corn-on-corn a carbon penalty.”
She recommends using a broadcast system in the fall and spring to have nitrogen in an easy to reach position for the microbes to feed. The faster they break down the residue, the faster that organic matter can start acting as a benefit on your field. If microbes don’t have enough to break down residue they will immobilize whatever nitrogen is out there—preventing it from getting into your crops.
“You can increase the efficiency of your nitrogen application early season by placing them in a starter band rather than in a broadcast in the spring,” says Brad Beutke, Farm Journal Corn College present. “Holds the nitrogen away from the carbon and feeds the plant.”
Nitrogen’s form has an impact on how quickly the plant can use it. There are four forms, ammonia, ammonium, urea and nitrate. Only ammonium and nitrate can be freely used by the plant without conversion.
Each of these forms comes with risk of loss. Here are the ways you can lose nitrogen in your fields:
- Volatilization, the loss of nitrogen as an ammonia gas.
- Anytime you have surface applied urea you can lose 15-20% in warm conditions.
- Nitrification converts nitrogen from ammonium to nitrate.
- Denitrification causes bacteria to convert nitrate to nitrogen gases that are lost to the atmosphere.
- Often takes place in waterlogged soil and needs ample organic matter to give bacteria energy. This is especially bad in high temperatures.
- Leaching is the loss of soluble nitrate as it moves with soil water. Leaching is worse in coarse textured soils since they have lower water holding capacities.
“If the plant is already showing signs of nitrogen deficiency the best form of nitrogen to fix the problem is the nitrate form,” Brad says. “That being said the nitrate form also has the highest risk.”
Nitrogen runoff can cause high nitrate levels in water supplies, for example consider the Des Moines Waterworks lawsuit. Nitrate levels are required to be lower than 10 parts per million to avoid methemoglobinemia (blue baby syndrome). In young, simple stomachs this syndrome depletes oxygen in the blood system and infants under six months are at high risk.
It is important to be aware of how you are losing nitrogen. The Des Moines Waterworks lawsuit has been eye opening to many and caused farmers in Iowa to reconsider their nutrient management strategies.
“You’re going to want to keep an eye on what’s happening to the Des Moines lawsuit,” Bauer adds. “I think overall, one thing we’ll be forced to do is manage nitrogen better.”