The Illinois Soil Testing Association Lab Accreditation Program (ISTA-LAP) has been developed to assure soil test results provided by participating labs serving the citizens of Illinois are within industry statistical norms of the test method. Based on this premise, soil test results from ISTA-LAP approved labs shall be accepted under the U.S.
Department of Agriculture NRCS (Natural Resource Conservation Services) code 590 of nutrient management, revised January 2012. The ISTA-LAP program is a voluntary program for laboratories seeking accreditation for soil testing in the state of Illinois. At the beginning of each year, the ALP coordinator will require a letter of acceptance from
the participating laboratories allowing the release of proficiency data to the ISTA-LAP proficiency assessor.
The ISTA-LAP proficiency assessor performs statistical analysis of the data as specified by the ISTA-LAP program. Laboratories providing soil test results within performance limits, will be placed on the ISTA list of approved labs and posted on the associations web site. Laboratories that fail to meet performance limits of the ISTA-LAP program, will
be offered a retest, and program for reinstatement.
Laboratories that wish to participate in the ISTA-LAP program will be required to:
- A member of ISTA
- Enrolled in the ALP Program for the calendar year
- Provide soil analyses by methods recognized by the ISTA, each ALP cycle.
(Recommended Chemical Soil Test Procedures for the North Central Region. (Revised) 1998. Missouri Agricultural Experiment Station SB 1001.)
The required soil test analyses methods are:
- pH H2O (1:1) and/or pH (1:1) 0.01 M CaCl2
- Phosphorus: Bray-1 P /or Mehlich 3 P SPEC or Mehlich 3 P ICP
- Potassium: NH4oAc Extactable /or Mehlich 3 K
Additional soil tests analyses are encouraged (i.e. buffer pH, exchangable cations, micro nutrients and soil organic matter) but are not required.
ISTA-LAP criteria for accreditation
Assessment of laboratory performance will be based on the laboratory analysis of five ALP soils (ALP test Code 801) each proficiency cycle by the proficiency assessor. Soil test performance limits criteria are listed in Table 1 by analysis method. Individual laboratory soil test results exceeding the listed performance limits of the statistical median, for each test method will be flagged for failure. ISTA accreditation shall be based on a 80% level of performance for each soil test method, across the five soils of each proficiency cycle. A maximum of only one soil test result could be flagged, to meet accreditation requirements of the ISTA-LAP program each proficiency cycle.
Laboratories failing to meet accreditation requirements shall be offered a retest soil sample set for the soil test method in question, and with a successful retest, their accreditation reinstated. Re-test soil sets will be provided within 15 days by the ALP Program Technical Director at a cost of $100. Laboratories which choose not to retest or
provide retest results within 30 days will be removed from the ISTA accreditation list. Laboratories failing the retest soil sample set, shall have an independent consultant review the lab’s method operation and performance at their costs, until it is determined by the ISTA-LAP assessor, they be provided a 2nd retest set at an additional cost of $75.
Laboratories failing on two retest sets will be removed from the accreditation list for 1 year. Once annually a yearend report will be provided to each ISTA-LAP laboratory listing a summary of the laboratory performance.