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Applying Anhydrous Ammonia Near Planting

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By: Pauley Bradley, Manager of Customer Outcome Marketing, John Deere

Anhydrous ammonia—which is injected into soil in a gaseous form—is a popular source of nitrogen fertilizer in North America due to its relative cost and longevity in the soil, compared to other nitrogen forms. Because of its stability in cold soils, corn farmers often apply anhydrous ammonia in the fall to get a head start on spring planting operations. However, if weather conditions prohibit fall or even early spring anhydrous application, the high nitrogen rates near the injection site can injure seedlings when seed is planted nearby only days after the application. When this occurs, farmers can maintain success by carefully positioning the two inputs using accurate placement technology and precision guidance.

 

Corn Yield By NH3 Depth and Rate

Wet conditions last fall and this spring in many parts of North America have prohibited field work including anhydrous ammonia (NH3) application. For corn producers committed to using anhydrous ammonia, applying the nitrogen (N) without compromising the seedbed, delaying planting, or damaging the crop can be a challenge. Environments typically considered higher risk for ammonia toxicity include coarse textured, dry, or high pH soils. However, damage can also occur in fine textured, wet soil conditions (Figure 1).

Corn seeding

A 3-year Midwest study (Woli, et al., 2014) investigated the impact of anhydrous ammonia rate and placement on corn grain yield in a low-disturbance tillage system. Anhydrous ammonia was applied at 4- and 7-inch depths at rates from 0 to 200 pounds of nitrogen per acre. Corn was planted directly over the ammonia band approximately one week following the NH3 application.

Seedling injury was not observed at the Kansas or Illinois sites, but was observed at the Iowa site in two out of three years. Injury there occurred when 160 and 200 pounds per acre of anhydrous ammonia were applied 4-inches deep one week prior to planting. The damage resulted in significant yield losses in those two years (Figure 2). No injury was observed when the ammonia was injected 7 inches deep.

Figure 1. Corn seedling damage from ammonia toxicity (photo courtesy of Iowa State University).

Observations at the Iowa location suggest that soil physical properties (i.e. moist, heavy soil) resulted in little soil fracturing and dispersion of anhydrous ammonia into surrounding soils during the preplant application. This, combined with the shallow placement, created a dense band of ammonia near the seed resulting in the seedling injury.

Figure 2. The impact of anhydrous ammonia rate and placement on corn yield (Woli, et al., 2014).

Corn yield chart

How to avoid ammonia burn

There are two ways to avoid crop injury from ammonia toxicity through placement (Figure 3):

  • Vertical separation (place anhydrous ammonia several inches deeper than the seed)
  • Horizontal separation (laterally offset seed trench several inches from the ammonia band)
separation chart

The rate and placement study referenced above showed that vertical separation can be effective in avoiding seedling injury in moist soil conditions. However, vertical separation may not be as effective in other situations. Horizontal separation can be an even more effective way to avoid seedling injury from ammonia toxicity. This is best achieved through automated machine guidance. For example, guidance lines can be generated for both the NH3 application pass and the planting pass using an application called Land Manager. Then enter a desired offset (i.e. 6-inches) to achieve the horizontal separation between passes when using John Deere SF3 or RTK levels of GPS accuracy.

Figure 3. Horizontal vs Vertical Separation of Anhydrous Ammonia from Corn Seedlings.

Angled Anhydrous Ammonia application

Historically, it’s been recommended to apply anhydrous ammonia at an angle to future corn rows to reduce the risk of ammonia toxicity. However, more recent observations suggest that applying nitrogen at an angle can reduce corn yields in one of two ways. The first is by injuring seedlings that lie close to nitrogen bands containing free ammonia (Figures 4 and 5). The second is by giving plants closest to nitrogen bands that don’t contain free ammonia a competitive advantage, thereby creating non-uniform growth (Figure 6), greater variability in ear size, and lower overall grain yield.

dark lines

Figure 4

Dark lines in the field are where anhydrous ammonia applied at an angle intersected with corn rows and reduced corn growth, resulting in shorter plants and reduced grain yield (Photo courtesy of John Deere).

short corn

Figure 5

Shorter corn plants and smaller ears near the middle of the photo are where the anhydrous ammonia band intersected the corn row resulting in plant injury (Photo courtesy of John Deere).

green stripes

Figure 6

Green stripes are plants located over nitrogen bands from the anhydrous ammonia application prior to planting. (Photo courtesy of John Deere).

Precision guidance as an alternative to angled application

Rather than using angled application to reduce the risk of ammonia toxicity, precision guidance can offset the entire corn row from ammonia bands and better mitigate the risk of ammonia toxicity. Additionally, giving all plants uniform access to nitrogen has also been linked to improved yields. A three-year study (Kovacs, et al., 2014) conducted by Purdue University demonstrated a 5.1 bushel yield increase (Table 1) when using precision guidance to apply anhydrous ammonia parallel to future corn rows versus at an angle (Figure 7).

tabel 1

Table 1

Source ‘Pre-Plant Anhydrous Ammonia Placement Consequences on No-Till Versus Conventional-Till Maize Growth and Nitrogen Responses’. Kovacs, et al., 2014.

tractor spraying ammonia

Figure 7

An angled anhydrous ammonia application being made at a Purdue University research farm investigating the difference between parallel and angled applications of anhydrous ammonia (Photo courtesy of Purdue University).

John Deere Solutions:

John Deere products and technologies provide several opportunities to manage anhydrous applications in a band that is placed parallel in a safe proximity to the corn seed row.

Leverage JDLink Connect to transfer those guidance lines and field plans to your tractor.

Summary:

Applying anhydrous ammonia parallel to and offset from future corn rows using precision guidance can be an effective alternative to angled anhydrous ammonia application. Additionally, yield benefits have been observed in parallel applications where plants are at less risk to ammonia toxicity and access to nitrogen is more uniform throughout the field. 

References

Kovacs, Peter; Van Scoyoc, George E.; Doerge, Thomas A.; Camberato, James J. and Vyn, Tony J.  2014.  Preplant Anhydrous Ammonia Placement Consequences on No-Till Versus Conventional-Till Maize Growth and Nitrogen Responses.  Agronomy Journal 106: 1746-1757.

Woli, Krishna P.; Fernandez, Fabian G.; Sawyer, John E.; Stamper, Joshua D.; Mengel, David B.; Barker, Daniel, W. and Hanna, Mark H.  2014.  Agronomic Comparison of Anhydrous Ammonia Applied with a High Speed-Low Draft and Conventional Knife Injection in Corn.  Agronomy Journal 106: 881-892.