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Choosing to use N inhibitors or not in Mid-South corn

Choosing to use N inhibitors or not in Mid-South corn published on 1 Comment on Choosing to use N inhibitors or not in Mid-South corn

by: Beatrix Haggard and Josh Lofton

The drying conditions in recent days have resulted in a percentage of corn finally being planted.  While most producers are focused on planting, these intense planting conditions will result in a short window for N fertilization. With this narrowed window between planting and N fertilization, it is time to start thinking about N management. In recent years, conditions at or near fertilization have resulted in high potential loss of applied N. These losses not only are detrimental to the surrounding environments but also to the production system, resulting in insufficient available N supply to the crop. The use of N inhibitors has been an increasingly common production practice in an attempt to minimize in-season losses. While the use of N inhibitors is a valuable tool for potentially decreasing N loss, proper management and proper selection are critical to decrease losses successfully.

Selection of the proper inhibitor is potentially the most critical aspect and can be challenging because of the numerous options available. Determining the right inhibitor varies, depending on N source, N application method, and field/environment.

Chemical names to ask for:

  • Urease inhibitors – NBPT (N-(n-butyl)thiophosphoric triamide), or NPPT (N-(n-propyl)thiophosphoric triamide)
  • Nitrification Inhibitors – Nitrapyrin, or DCD (dicyandiamide)










Figure 1. Untreated urea at 240 lbs N/acre.











Figure 2. Super U urea at 240 lbs N/acre (NBPT and DCD).



Urease inhibitors:

Urease inhibitors function by inhibiting the urease enzyme, a natural enzyme in the soil system that hydrolyzes urea into ammonium. By doing this, urease inhibitors attempt to minimize volatilization losses during periods favorable to volatilization (dry, windy, urea on surface). When environmental conditions exist, namely moisture, urease inhibitor activity is diminished, allowing the urease enzyme to break down the urea. Urease inhibitors work very well with granular fertilizers because these are frequently surface-applied with limited to no incorporation. With surface application of granular fertilizers, volatilization is the primary potential loss, at least during early season when adequate moisture does not exist. However, these inhibitors are not only beneficial on granular fertilizers. Substantial volatilization can occur with liquid fertilizers that are surface-applied in warm, dry conditions with little soil moisture. When these same fertilizers are incorporated, such as being knifed-in in lieu of surface-applied, as little as 1-5% of applied N is typically lost through volatilization. Therefore, urease inhibitors are most effective when urea-containing fertilizers are surface-applied, whether liquid or granular, without incorporation.

Nitrification inhibitors:

Nitrification inhibitors function by inhibiting the soil bacteria, which are required for nitrification to occur. Inhibiting nitrification keeps more N as ammonium for longer periods of time. This is beneficial because it can limit or minimize both leaching and volatilization losses, both of which occur as nitrate compared to ammonium. These inhibitors have the potential to be the most universally beneficial in high rainfall and irrigated systems especially. However, the benefit of these products has not been widespread in research trials conducted across the Mid-South. A two-year study conducted at the LSU AgCenter, however, did show that these inhibitors can be beneficial in Louisiana systems. The best management of these inhibitors is to know their limitations. Research conducted at the LSU AgCenter as well as other research around the US indicate that these products last only 10-30 days. Therefore, these inhibitors provide early season “protection” of the N fertilizer, but N can still be lost after the nitrification inhibitor has degraded.


Unlike the other inhibitors, coated-fertilizers do not inhibit any process within the soils system but slowly release N from the coated source throughout the season. By slowly releasing N into the soil system, these inhibitors minimize only the amount of N applied that can be lost through individual loss mechanisms. These N sources are promising at minimizing both volatilization, denitrification and leaching. However, few if any coated liquid sources are currently or will be commercially available in the near future. Therefore, these must be used solely on granular fertilizer sources. Additionally, because the fertilizer is slowly available, N available from the applied fertilizer during early season growth is minimal. Therefore, high amounts of residual soil N need to be available, or supplemental N fertilizer needs to be supplied.


Nitrogen inhibitor products have the potential to be very beneficial tools at managing N fertilizer additions in Louisiana production systems. However, if mismanaged, not only do you lose the benefit of applied inhibitors but also narrow the economic potential of the production system. Therefore, time needs to be given to selection of a particular inhibitor to fit the system as well as proper management within the production system.


If you have any further questions, please contact your local extension agent or specialist.

Beatrix Haggard, Upland Row-Crops Soil Fertility Specialist – (318)498-2967

Josh Lofton, Agronomist – (318) 498-1934

Get the “Dirt” on SoilWeb – Phone App Review

Get the “Dirt” on SoilWeb – Phone App Review published on No Comments on Get the “Dirt” on SoilWeb – Phone App Review

We have reached a point in society where most of the population is talking about information overload. For some relief, this fact sheet provides information and background on the SoilWeb phone application. The phone used for this was an iPhone® 5s; the author did not have an AndroidTM to test.


  • Great app for general knowledge of what soil series are found in your fields or property.
  • Beneficial for understanding any major soil features that could be problematic in your fields – clay pans, natric horizons (salt), fragipans, etc.
  • Should NOT be used for determining soil pH and organic matter percentage.
  • If a field has been precision-leveled, caution should be taken for soil textures.


SoilWeb is a great starting point for determining soil series located on your farm. But as with any Web application, there are limitations. First, let us look at how we use the app.

  • There is an information button in the top right-hand corner of the application. When you click here, the accuracy threshold, which is in the lower left-hand corner can be adjusted. This is letting you know how accurate your GPS is on your phone. This will depend on if you are under any structures or dense vegetation and your cell phone coverage. The smaller the number, the better. At best you will typically be around 10-20 m.


  • Once the accuracy has been set, then you can select the Get My Location button at the top of the application screen. The application will then display a picture representation of the soil series, which accounts for color and horizon depths.


  • You can then click on the soil series name that is blue, and it will take you to a screen displaying data concerning the soil series taxonomic description and lab data from the original data collected for the series. This is the point when we start to look at the limitations of this application for production agriculture.



  • Basic understanding of texture changes throughout a field.
  • Knowledge of some limiting horizons that could be present in a soil. (If you look at the last screen shot and notice how the percent clay increases 10%, this increase is the reason why Gigger soils have issues forming a plow pan due to the clay pan already present from soil formation.)
  • The application is also showing what percentage of other soils might be found. There is an 85% that can be seen after the soil series name. This is basically saying that in normal situations that of a 10-acre field, 8.5 acres would be Gigger and 1.5 acres would be another geographically associated soil (i.e. a soil typically found nearby).


  • Soil series descriptions provide information collected when the soil was originally described or whenever the series was updated. In the case of the Gigger, the chemical data is from 1992, which is more recent than when the soil was originally mapped in 1979.
  • Management practices can change properties in the soil.
    • pH has likely been altered by lime applications. Therefore, depending on the value found on the phone app, would not be recommended.
    • Texture would be affected if a field was land-leveled. This is especially true for any soils that are Alfisols (Gigger, Calhoun, Crowley, etc).
    • Organic matter is heavily influenced by management practices and will typically be different than what is shown on this phone app.

The disadvantages are listed not to discourage the use of the application but to know its limitations. The application is a great tool when you start trying to figure out what might be happening at deeper depths in the field that could cause problems or be beneficial.

If you have any questions concerning the use of this phone app or any of the data it provides, please contact:

Beatrix Haggard – (318) 498-2967  –

  • Developed by Dylan E. Beaudette and Anthony T. O’Geen of the Soil Resource Laboratory at the University of California-Davis
  • Data sourced from USDA-NRCS Soil Survey data (SSURGO)