The geographic framework shown here delineates spatial units with shared soil and climatic properties, where one might expect agronomic tools and/or products to perform similarly, if all other farm management variables are constant. AGROTAIN® trials conducted using urea, UAN or both are super-imposed on the framework, which we refer to as Technology Extrapolation Domains or TEDs. Please see the text below for more explanation of how this framework is being used to show trial results.

AGROTAIN® Trial Locations and the TED Framework

Field trials play an important role in the testing and implementation of new agricultural products and management practices. Properly conducted trials give a good indication of a products’ performance in the soil and climatic conditions present at the trial site. However, extrapolating results from field experiments conducted at one or more locations to a larger, spatially explicit domain has been a major challenge confronting agronomic science due to the large variation in soil properties and climate governing crop response to management.

The heart of the challenge is to achieve a balance between having a spatial scheme that is so coarse that environmental variation within a technology extrapolation domain (TED) is large—leading to substantial variation in performance of a given technology, or so fine that the number of field study locations and data requirements are overwhelming. Recent advances in geographic information technologies and publicly accessible databases on soils and climate now make it possible to establish such a framework.

The framework NutrientStar uses draws heavily on the spatial scaling protocols developed to support the Global Yield Gap Atlas developed by Drs. Ken Cassman, Patricio Grassini, Justin Van Wart and the University of Nebraska.

The TED framework delineates spatial units with shared soil and climatic properties, where one might expect agronomic technologies to perform similarly, all other variables being constant. On the map above, TEDs are depicted as colored regions with trial locations indicated by icons, which are colored according to fertilizer form. These TEDs correspond to the areas of greatest rain-fed corn production in the US.


AGROTAIN® is for use with all crops to reduce ammonia volatilization.


Farmers who wish to increase NUE by reducing ammonia volatilization.


AGROTAIN® is a urea fertilizer additive.

Table of AGROTAIN® Studies Sorted by TED Region and Ranking

The tables below provide information about yield impacts of AGROTAIN in plot studies grouped according to the TED where the study was conducted. The NutrientStar team had to estimate which TED a study was located within, because precise GPS coordinates were not provided for most plot studies. To make this estimate, a buffer of 5 km was drawn around each study location, and the TED represented by the largest number of pixels within the buffer was chosen as the TED for that study, after eliminating all pixels without corn/soybean production. The column in the table showing the estimated TED for each study is entitled “Plurality TED”.

The confidence level for each grouping of studies is the percentage of pixels within the 5 km buffer representing the plurality TED – again, after eliminating all pixels without corn/soybean production. Confidence levels are categorized and color-coded as: high confidence (greater than 75% of pixels in buffer = green), medium confidence (greater than 50% to 75% of pixels in buffer = yellow), and low confidence (less than 50% of pixels in buffer = red).

Each TED is also ranked in terms of its importance to corn production in the Eastern US, both by number and by percent. For example, in the first set of studies conducted by Varsa et al, there is a medium confidence level that the plurality TED is accurate for the study, and that TED is ranked fourth in terms of area in corn production in the Eastern US, representing 4.3% of corn production. Studies that were conducted in TEDs that do not fall within the top 75% of corn-producing areas, or that were conducted in Canada, are shown in the table in grey shading. The weighted mean values for delta yield in bushels per acre and delta yield in percentage for the entire data set are also shown at the bottom of the table.

AGROTAIN®, made by Koch Agronomic Services, is used to treat dry and liquid nitrogen fertilizers to slow the conversion of urea to ammonia gas. Slowing the conversion of urea to ammonia should decrease losses of nitrogen to the atmosphere.

AGROTAIN® has the potential to decrease nitrogen losses only when urea is applied to the soil surface. Injection or incorporation of urea into the soil will cause the urea to convert to ammonia in the soil where there will be sufficient moisture to immediately change the ammonia to ammonium, which is not a gas and is held tightly to the soil.

Product Description and Mode of Action

AGROTAIN® is an additive targeted to fertilizers that contain urea. The purpose of AGROTAIN® is to reduce ammonia volatilization after fertilizer application. The active ingredient, NBPT, functions as a urease inhibitor. Urease inhibitors reduce the speed of conversion from urea in fertilizer to ammonium (enzymatic hydrolysis), which can then either rapidly convert to gaseous ammonia and be lost to the air or convert to nitrate (NO3-) and be subject to leaching losses. By staying longer in the urea form, the fertilizer can more slowly become available to plants, increasing the chance of being there when needed by the crop (Trenkel 1997).

Research Results from Field-Scale Strip Trials

NutrientStar reviewers found no published research results from field scale strip trials.

Research Results from Chemistry Trials

Note: Chemistry trials can provide information concerning the effectiveness of a product in laboratory and greenhouse settings but do not provide information related to a products effectiveness in the field.
NBPT, the active ingredient in AGROTAIN®, was identified in early laboratory studies to be a good repressor of urea hydrolysis, even when applied at low concentrations (Beyrouty et al. 1988; Bremner and Chai 1986; Hendrickson and Douglass 1993; Watson et al. 1994).

Research Results from Small Plots

An intensive and extensive review of the literature was completed to assess the effectiveness of AGROTAIN® to increase yield of corn and wheat. All the research was completed on small plots. Typical plot dimensions were 15 feet wide by 40 feet long, and although plot sizes varied, none were greater than 1/2 acre in size.


The average yield increase measured for AGROTAIN® when AGROTAIN®-treated granular urea or liquid urea ammonia nitrate (UAN) was compared with non-treated urea or UAN was 10 bushel/acre, with a 95% confidence interval of 7 to 13 bu/acre..


The average yield increase measured for AGROTAIN® when AGROTAIN®-treated granular urea or liquid urea ammonia nitrate (UAN) was compared with non-treated urea or UAN was 3 bushel/acre, with a 95% chance of obtaining a yield increase of 1 to 5 bu/acre.

For more information about small plot results on the effectiveness of AGROTAIN® to increase yield please visit the AGROTAIN® research findings page.