Illinois Soil Testing Association

ISTA's Lab Proficiency Testing Program

The Bulls-Eye of Consistent Quality and Consistent Results

The ISTA knows that farmers and others in need of soil analysis require reliability,
consistency and accuracy.  ISTA membership is proof positive that a soil testing
laboratory strives to meet these expectations.

Members of ISTA are required to participate in a quality control program referred to as
the Split Sample Soil Test Comparison Program.  In this process, six samples are sent
quarterly to all member labs.  The labs test the soil and return the raw data to an
independent accounting firm.

This information is then gathered yearly and used in a Reliability/Repeatability report. A
level of proficiency is required to receive a Certificate of Good Standing from ISTA. This
certificate is the member's accreditation and is their clients' assurance that the
information they receive is reliable, consistent and accurate.

North American Proficiency Testing Program

Some ISTA member labs also participate in an additional National Proficiency Testing
Program (NAPT). This program compares laboratories across the country and offers an
outreach program for laboratories to help improve the quality of their results.

Participating laboratories complete sample analysis and provide results to the NAPT
program coordinator for statistical evaluation. Quarterly, each laboratory receives an
evaluation of their individual performance on each of the methods listed. Annually, the
program provides a report to each participant of the performance of the individual
laboratory and that of the agricultural laboratory industry.