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. NutriSphere® trials conducted using urea or UAN 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.
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.
The tables below provide information about yield impacts of NutriSphere-N® 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 Mulford, there is a low confidence level that the plurality TED is accurate for the study, and that TED is ranked 45th in terms of area in corn production in the Eastern US, representing 0.4% 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.
NutriSphere-N® (also known as NutriSphere-N® Nitrogen Fertilizer Manager, or N-N) is a polymer-based, enhanced-efficiency fertilizer product made and distributed by Verdesian Life Sciences that can be combined with various N fertilizer sources. It can be coated onto granular fertilizers like urea, or injected into UAN solutions. Like many enhanced efficiency fertilizers, NutriSphere-N® is advertised to improve crop consumption and increase yield by decreasing the rates of nitrogen loss via volatilization, leaching, and denitrification through suppression of urease and nitrification activity. NutriSphere-N® is a relatively new enhanced-efficiency fertilizer product, but it has been tested in the laboratory and a variety of North American field locations since the early 2000s. It has also used by farmers on over 30 million acres in 40 states (Verdesian 2015).
NutriSphere-N® is intended for use with all crops for decreasing nitrogen loss.
Farmers who wish to increase NUE by reducing nitrogen losses.
Varies based on volume.
NutriSphere-N® is a polymer product that is applied to granular fertilizers or UAN solutions
NutrientStar reviewers found no published research results from field scale strip trials.
Laboratory results are mixed. The NutriSphere-N® polymer was evaluated in early laboratory experiments on jackbean at the University of Kentucky, where it was shown to inhibit nitrification as well as urease activity, with the amount of inhibition ranging from 22 to 46% (Coyne 2009). Following other laboratory experiments in North Dakota and Arkansas, Franzen et al. (2011) concluded that NutriSphere-N® had “no nitrification or urea volatilization inhibiting properties”. Some of the same researchers continued laboratory work, and found that NutriSphere-N® did reduce ammonia volatilization from UAN fertilizer, but with a much lower efficacy than ammonium thiosulfate, NBPT, and calcium thiosulfate (11%, compared to 40%, 51%, and 40%, respectively) (Goos 2013a). The same research lab found very little urease inhibition from NutriSphere-N® (it depended on the rate, at high rates of 500 mg/kg, there was some inhibition, but not nearly as much as with NBPT) (Goos 2013b).
An intensive and extensive review of the literature was completed to assess the effectiveness of NutriSphere-N® to increase corn yields. All the research was completed on small plots, with none greater than 1/10 of an acre.
The 14 plot studies averaged yield gains of 8 bushels/acre, with a confidence interval range of 2 to 14 bu/acre.
With the data available, and in the conditions studied, NutriSphere-N® failed to improve crop yield in a consistent manner particularly for wheat, even though certain studies found it to be promising. Even with some indication of yield benefits for grain corn, and because of the lack of studies testing N losses, the available data are too limited to conclude that this product improves yield across the board or provides other significant improvements in N efficiency. Therefore, if the product is to be considered further for such purposes and there is any expectation of effectiveness under specific conditions, proof of such is needed. This would require more data collection.
For more information on NutriSphere-N® and to view the complete report – including references – please visit the NutriSphere-N® research findings page.