In defining the minimum parameters for data that would be adequate for assessing NUE products and technologies, the NutrientStar Review Panel imposed the following requirements:

• Data should be from the United States or Canada
• Data should include metrics for assessing NUE (N rate and yield)
• Data should be collected from commodity crops (corn and wheat)

The reasons for placing restrictions on what the program considers acceptable data for an assessment are further outlined below.

Currently the NutrientStar Program focuses on assessing data related to the performance of NUE tools which have been obtained primarily from corn and wheat trials. This is not a reflection on the potential for many of the assessed tools to provide benefits to other crops – including specialty crops.

The NutrientStar program chose to focus on corn and wheat initially because these are the crops with the largest agronomic footprint and greatest potential for achieving higher levels of NUE. In addition, the criteria and parameters for measuring effectiveness of products for commodity crops and for specialty crops would be different, given that corn and wheat producers are much more focused on yield goals, while specialty crops demand a greater focus on the quality of the end product.

In fact, in many of these crops (e.g. vegetables or turfgrass) the profitability of the crop is largely or exclusively quality-dependent. This can make data difficult to compare as measures of quality are not only more difficult to quantify but also vary widely between crops, varieties, seasons, and markets. While it may eventually be feasible to assess the effectiveness of NUE tools in other crops those assessments are not yet a focus of the NutrientStar Program.

Currently the NutrientStar Science Review Panel seeks data from field trials conducted in the continental United States and Canada. While it is true that many of the tools being assessed as part of this program are being used and tested in other countries, the comparability of those assessments to agriculture conducted in a US context is unknown.

The primary hurdles to using data from field trials conducted outside of the continental United States and Canada are environmental variability and diversity in agricultural practices.

The variability of weather and soil conditions is such that data from one US state is often not reflective of the conditions in other US states. This problem is magnified when using data from other countries.

Agricultural practices can vary widely between countries due to differences in economic status and technological sophistication. These differences can have a substantial impact on the performance of NUE tools.