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PFR Report: ANHYDROUS AMMONIA

Published on Wednesday, March 3, 2021

Nitrogen is one of the 16 essential elements required for plant growth. The most common nitrogen fertilizer forms include anhydrous ammonia (NH3), urea, and urea-ammonium nitrate (UAN) solutions. Anhydrous contains 82% nitrogen, the highest amount of any nitrogen fertilizer. Once applied in the soil, anhydrous ammonia converts to the ammonium form (NH4+). Ammonium ions are very stable in the soil. Over time, ammonium converts to nitrate (NO3), which is the form of nitrogen most used by plants.

 

Anhydrous is one of the largest nitrogen fertilizer sources in the US because of its high nitrogen content, stability in the soil, and low production cost.

 

With anhydrous being such an important fertilizer for corn producers, it is important that we understand the most practical ways to use it on our farms. Let us start by understanding how anhydrous moves in the soil, with a learning project the PFR team did in 2020.

 

The purpose of this project was to understand how nitrates and ammonium move in the soil. Soils were sampled four weeks after the anhydrous application and again eight weeks after the anhydrous application. Soil cores were taken every 3 in. starting at one corn row and moving to the next corn row.

 

 

The results show a high level of ammonium at the 15-inch sample for the 4-week POST application soil samples. This was expected since the anhydrous was placed between the rows.

 

4-Week POST Application Nitrate and Ammonium Average for All Locations

 

Interestingly, the 8-week POST application samples show a higher amount of nitrate in the soil than ammonium. However, it was still concentrated at the 15-inch sample directly between the rows.

 

8-Week POST Application Nitrate and Ammonium Average for All Locations

We know that a majority of the corn roots are within 7 in. of the plant, so does it pay to apply anhydrous underneath the rows? How deep should it be applied, and how soon can we start planting after the application? These are questions that Beck’s PFR is trying to answer.

Beck’s PFR has four studies that involve anhydrous ammonia. These studies include application depth and timing, application placement, nitrogen systems, and fall vs. spring-applied anhydrous ammonia.

The purpose of the depth and timing study is to evaluate planting intervals after a pre-plant incorporated application of anhydrous, placed at two different depths. The depths included 4 in. and 8 in., and the planting intervals were 2 and 7 days after the anhydrous application.

Results from 2020 show that shortening the window between application and planting is possible if the anhydrous is applied at an adequate depth.

4 in. Depth Planted 2 Days After vs. 8 in. Depth Planted 2 Days After

 

Our two-year data shows that the depth of anhydrous applications is the key to avoiding seedling injury. When applying anhydrous a short time before planting, it must be placed deeper or seedling injury and yield loss is likely.

 

 

The goal of the application placement study was to evaluate the yield impact of placing two different rates of pre-plant incorporated anhydrous between the rows versus under the rows. The majority of corn roots are within 7 in. of the plant and capture 80% of the crop’s nutrients. With the anhydrous placed directly below the plant, roots could access the nitrogen earlier in the season. This resulted in higher plant concentrations of nitrogen and a slightly higher yield in 2020.

 

 

The last anhydrous study the PFR team did for 2020 was the nitrogen systems study. The purpose of this study was to evaluate various methods of nitrogen applications and timing and their effect on yield.

 

 

Beck’s PFR data over the years has confirmed that split applications pay. Nitrogen applied closer to the rows helped set the stage for excellent ear determination during the V5 through V12 growth stages.

New for 2021, Beck’s PFR is testing fall vs. spring-applied anhydrous. Fall nitrogen fertilizer applications continue to be popular for several reasons, including lower cost, time for application, equipment availability, often better soil conditions, and competing springtime field activities. Disadvantages of fall-applied anhydrous can be the loss of nitrogen between application and crop use and environmental concerns with nitrate runoff and leaching.

With spring fieldwork right around the corner, there is still time to apply anhydrous if it was not done last fall. Remember, the closer the anhydrous application is to planting, the deeper the application needs to be. Planting is still the most important pass, and if nitrogen is not applied pre-plant, it can still be successfully applied after planting.

Have a safe and successful spring!

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Author: Chris Grimm

Categories: PFR, PFR Reports

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