Selecting your soil physical testing lab

By Norman W. Hummel, PhD

The athletes on your favorite sports team are pros. Their sport is their profession and they work full time to condition their bodies and to hone their skills so they can be the best they can be. Their teams and careers depend on it. They are not part-time athletes.

The construction of a new sports field is a major investment. The soils lab you decide to work with for your construction project will be your teammate. Why then, would you even consider someone or some company that only performs these tests on a part-time basis? Also, what assurances do you have that the lab you are working with is even qualified to perform the testing required for your project?

I have wanted for some time to write an article explaining what lab accreditation is and what it can mean to those who require soil physical testing. Now that I am out of the testing business, I feel free to do so without giving the impression of promoting my own business.

Whether the field is sand- or soil-based, testing the physical properties of the soil- or sand-based mix is a key component to the field’s success. In the case of the soil-based field, it may be just a matter of finding out the soil texture and organic matter content to provide you or the owner with some reasonable expectation of how the soil and field will perform. The testing may provide some guidance on how to improve the soil with amendments.

The sand-based field requires more extensive testing. Soil physical testing of the sand-based mix and under drainage stone materials is a risk assessment. Rootzone mixes that meet certain particle size and performance properties have a much higher probability of succeeding. If an experienced testing provider is involved, it can go beyond just this “risk assessment” to the point that an optimum mix can be identified with the construction materials available.

The test methods used to evaluate mixes can be found in the American Society of Testing and Materials (ASTM), so they are available to anyone who wishes to purchase them. It is important to understand, however, that not all labs are equal even though they may be performing the same tests.

In the 1990’s the USGA developed new guidelines for greens construction and the test procedures supporting the guidelines. These ASTM procedures are still used today for the evaluation of sand-based rootzone mixes. The USGA also felt that there was a need to involve a 3rd party accreditation organization to recognize soil physical testing laboratories that meet international standards for testing laboratories. Since 1995, the American Association for Laboratory Accreditation (A2LA) has be accrediting labs performing soil physical testing of greens and sports field mixes. To this day the USGA will not recommend a lab unless they achieve A2LA Accreditation.

Accreditation by A2LA is a rigorous program that requires laboratories to follow strict quality control protocols. The checklist of required items is more than 40 pages long and includes traceability of every single measurement in the lab to a national calibration standard (National Institute of Standards and Technology standards). Labs are required to have assessments done every 2 years by outside A2LA assessors who examine among other things, equipment, calibration records, training records, and the test procedures being performed by lab technicians.

In addition, all accredited labs are required to participate in proficiency testing (PT) programs for all of the test procedures they are accredited for. A PT program is one whereby rootzone mixes or other samples are sent by a PT provider to all participating labs for testing. There is a PT program specifically for sand-based mixes; that program originated at Colorado State University. The test data is sent back to the PT provider, analyzed, and compared to that of all of the participating labs. If any of the 69 test values submitted by a lab deviate from the median of all participating labs by some set amount, that lab is issued a warning for that test. The lab is then required to perform an investigation on that deviation and to correct the problem, if one exists.

Minimally, any lab that performs physical testing on sand-based rootzone mixes should be participating in a PT program. If not, there is absolutely no way they can validate the accuracy of their test data. Their data could be way out in left field without the lab or their clients even knowing it.

Lab accreditation is very expensive for those labs that participate in the program. As the owner of a lab that was accredited for 18 years, I often looked at the cost/benefit of the program. Strictly from a business standpoint, it made little sense to maintain accreditation since it is unlikely that it resulted in any significant increase in business. Where I saw the most benefit in accreditation, however, was in my confidence that our data was good data. I also felt that the data from an accredited lab would be more defensible than a non-accredited lab should the data ever be called into question in a legal dispute. I can envision a good attorney easily discrediting the data from a non-accredited lab, especially if that lab does not perform the tests regularly or if theirs is a part-time test lab in the basement or garage of their home. Accreditation not only offers some protection to the lab, but also to the contractors or suppliers that use a lab, and certainly the designers that specify an accredited lab.

An oft-misunderstood requirement for accreditation is a minimum educational/experience level for staff. I stress the term “minimum.” While all accredited labs perform the tests the same way, the level of agronomic expertise within the lab to interpret test results and make recommendations will vary among labs. Most labs are adequately staffed in this regards to compare test results to a construction specification. It will be in cases where the project is more complicated that differences in agronomic expertise will separate out the accredited labs.

No professional sports team would bring an unqualified wannabe off the streets onto their team to save a few bucks. Selecting a soil physical testing lab that is accredited provides you with some assurance that your team mate is a pro and qualified to properly carry out the testing you need.

Dr. Norm Hummel owned and operated Hummel & Co. Inc laboratory for 20 years and now works as an independent soils consultant. The former Hummel & Co. lab now operates as Turf and Soil Diagnostics with labs in Linwood, KS and Trumansburg, NY.