The Three “I’s” of Anhydrous Ammonia Injury
January 15, 2024
Introduction
When diagnosing anhydrous ammonia injury, there are three “I” s to consider. Those include identification of the symptoms, investigation of what may have happened, and how to avoid this incidence going forward.
Identification
Poor emergence is not what a grower likes to find after planting. One of the first steps is to observe the field and note what is visible and not visible. Visible symptoms are uneven emergence, wilting plants, and a notable pattern across the field. The non-visible symptoms require digging to examine the roots for any deformities such as discolored seed and burnt back roots (Figures 1 and 2). After symptoms are identified, an investigation step is needed.
Investigation
Questions to ask:
Was anhydrous ammonia (NH3) applied? When was it applied in relation to planting? How much was applied? What depth? What were the soil temperatures and moisture conditions?
These questions can help determine why there are issues. But, for this crop, the damage is done, and a replant may be needed. Education is important to help mitigate risk moving forward.
Incidence
How can a grower minimize potential seed or seedling injury while applying NH3 in the spring, ahead of planting? The most vital information to remember is to separate corn seed and NH3 with time and/or distance. There is no magical number of days to delay planting after application. The rule of thumb is five to seven days or longer, but it’s not a guarantee. It is exceedingly difficult to predict when and if NH3 injury might occur.
Application depth and direction matter. Injection depth should be a minimum of six inches.1 A depth of 8- to 10-inches should be considered to help reduce the potential for anhydrous seedling injury. At the point of knife release, there is a 3- to 4-inch NH3 expansion zone. With shallower applications and the expansion zone, seedling roots are more likely to come in contact with the NH3 and be injured.1 Regardless of when the anhydrous was applied, when planting corn, the rows should be offset 4- to 6-inches from the anhydrous application slot to reduce the potential for seedling injury.1 If the planted row is offset by the 4 to 6 inches, planting can potentially occur the same day as the anhydrous application.1 Because of soil properties, there have been instances of seedling injury when planting occurred two weeks or more after the application, even after a fall application.2 Consideration should also be given to applying the anhydrous diagonally to the planned corn row direction; however, when a seed is planted over the diagonal application site, injury can potentially occur.
Spring Application Guidelines
- Use GPS guidance to plant corn rows 4 to 6 inches away from anhydrous application slot. Do not plant directly over ammonia injection tracks.
- Consider applying anhydrous at an angle to future corn rows.
- Anhydrous ammonia should be injected at a depth greater than 6 inches.
- Consider applying some nitrogen via sidedress to lower preplant rates.
- Do not apply in wet soils as knife slots may smear and result in ammonia being lost to the environment.
- Wait as long as possible before planting to allow for ammonia to convert to a safer nitrogen form.
- Consider switching to an alternate source of nitrogen, such as UAN solutions or urea.
Another option to consider is applying NH3 in the fall. A fall application is often a good option because cost is usually lower, there can be more time for application, and soil conditions are often better for injection. Fall applications can also help reduce soil compaction and spread out the workload for more timely spring planting. Success of fall applications can be increased by applying when soil temperatures drop below 50 °F at the 4-inch depth and with continuing cooler conditions forecasted.3
One additional option is splitting the application. If conditions are not ideal for a fall application (warm soil temperatures extending into late fall or wet soil conditions), the window for injection may be small. Therefore, having an alternative plan that may include split nitrogen applications may be beneficial. A potential solution may be a fall application on the fields best suited for nitrogen retention and delaying the application until spring on fields where NH3 is not well suited. Splitting applications in the fall and spring can help minimize many of the disadvantages associated with a single large fall or spring application by applying a lower rate in both the fall and spring. Applying some NH3 in the fall can provide what the crop needs to get started in the spring. Applying the remainder in the spring, closer to when the plant needs nitrogen, helps to increase efficiency, and reduce the potential for loss by leaching and denitrification.
In conclusion, according to Emma Orchardson of CIMMYT (International Maize and Wheat Improvement Center) “Nitrogen is the most essential nutrient in crop production but also one of the most challenging to work with.”4 The 4 R’s of crop nutrition (the right source, the right rate, the right placement, and the right timing) should be considered.5 Anhydrous ammonia can be a great nitrogen fertilizer source for crop production; however, due to its unique properties, there are important characteristics and safety precautions that should be understood and followed when choosing to implement NH3 into you crop nutrition program.
For additional NH3 application information, please see Fall and Spring Anhydrous Ammonia Applications.
Channel Agronomist
Kristin Schiff
Sources
1Sawyer, J. 2019. Anhydrous ammonia application – spring 2019. ICM News. Integrated Crop Management. Iowa State University Extension and Outreach. https://crops.extension.iastate.edu/cropnews/2019/03/anhydrous-ammonia-application-spring-2019
2Nafziger, E. 2015. Nitrogen management – avoiding ammonia injury. farmdoc. Department of Crop Sciences. University of Illinois at Urbana-Champaign. https://farmdoc.illinois.edu/field-crop-production/crop_production/nitrogen-management-avoiding-ammonia-injury.html#:~:text=Seed%20and%20seedling%20damage%20from%20spring-applied%20NH%203,sites%20and%20is%20not%20damaging%20to%20plant%20tissue.
3Fontes, G.P., Jones, J. and Nafziger, E. 2024. Considerations for fall application of anhydrous ammonia. The Bulletin. farmdoc, Department of Crop Sciences, University of Illinois at Urbana-Champaign. https://farmdoc.illinois.edu/field-crop-production/considerations-for-fall-application-of-anhydrous-ammonia.html
4Orchardson, E. 2020. Nitrogen in agriculture. CIMMYT. Nitrogen in agriculture. https://www.cimmyt.org/news/nitrogen-in-agriculture/
5Rogers, E. (Fronczak, S.) 2019. The 4R's of nutrient management. Field Crops. Michigan State University Extension. https://www.canr.msu.edu/news/the-4r-s-of-nutrient-management
Additional sources
Sawyer, J. 2019 Understanding anhydrous ammonia application in soil. ICM News. Integrated Crop Management. Iowa State University Extension and Outreach. https://crops.extension.iastate.edu/cropnews/2019/03/understanding-anhydrous-ammonia-application-soil
Maharjan, B., Iqbal, J., Puntel, L., and Rees, J. 2023. Fertilizer-nitrogen injury to corn. CROPWATCH. University of Nebraska- Lincoln. https://cropwatch.unl.edu/2023/fertilizer-nitrogen-injury-corn
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