The North American Proficiency Testing (NAPT) Program (a program of the Soil Science Society of America) assists soil, plant and water testing laboratories in their performance through inter-laboratory sample exchanges and a statistical evaluation of the analytical data.
The program guidelines have been developed for the agricultural laboratory industry by representatives from groups familiar with and involved in standardizing methods and developing nutrient recommendations for soil and plant analysis methods within the U.S. and Canada. It is operated as an activity of the Soil Science Society of America and overseen by an oversight committee comprised of representatives of the above-mentioned groups. These include: Regional Soil and Plant Analysis Workgroups; Scientific Organizations; State/Provincial Departments of Agriculture; and private and public and plant analysis labs. Retrieved from: http://www.naptprogram.org/
Our lab participates in the North American Proficiency Testing program.
Here are our results: