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In-Person Training for Mulch and Soil Testing at the WWMA Annual Meeting

David speaking in front of bags of mulch and soil at training

Now that we are attending meetings in-person again, this presents an opportunity for OWM staff to provide some of our training directly to our stakeholders while we are all together at the various weights and measures association meetings. As the hosts for the Fall 2022 Western Weights and Measures Association (WWMA) meeting, Orange County (CA) Weights and Measures organized and coordinated an in-person training for attendees that included a session from NIST OWM on testing packaged mulch and soil using the test procedure in NIST Handbook 133 Section 3.10. Mulch and Soils Labeled by Volume. Over 45 officials were in attendance people across 9 states (AK, AZ, CA, CO, ID, MT, NV, NM, and UT).

Believe it or not, there are some big differences between mulch and soils when it comes to determining the volume of packages using the Handbook 133 test procedure. Specifications are provided in the test procedure for constructing the various size test measures needed to ensure the proper size test measure is used that must accommodate the entire contents of the packaged being tested.

Here are some general definitions for mulch and soil as found in the test procedure:

Mulch and soil

Mulch is defined as “any product or material except peat or peat moss that is advertised, offered for sale, or sold for primary use as a horticultural, above-ground dressing, for decoration, moisture control, weed control, erosion control, temperature control, or other similar purposes.”

Soil is defined as “any product or material, except peat or peat moss that is advertised or offered for sale, or sold for primary use as a horticultural growing media, soil amendment, and/or soil replacement.

Even though these horticultural products are packaged and labeled similarly, their innate physical characteristics, like variable and irregular particle sizes, wood resin stickiness, and moisture retention tendencies result in a significant difference in how each material ‘clumps’ within its packaging when exposed to the elements (i.e., rain or excessive humidity). This may cause post-production compaction from storage, transportation, and handling throughout the distribution supply chain.  

David pouring a bag of soil

Mulch is generally comprised of organic, shredded plant-based material whereas soil is a composite mixture of sand, clay, silt, and organic matter such as forest products, leaf humus, animal manures, compost, and more. The increased permeability of soil allows the moisture to drain away more readily; in contrast (and by design), mulch can retain moisture much longer and more effectively than soil. Any excess moisture may add significant weight to the mulch particles and thus distort the volume test results. With this knowledge, an inspector needs to avoid mulch test samples that contain an excessive amount of collected moisture within the packaging.  

Thus, it is important to consider these key elements during the test:

David speaking at mulch and soil training
  • Choosing the correct size test measure for the volume to be evaluated.
  • Properly de-clumping the product to ensure it is loose and free flowing before pouring the contents into the test measure.
  • Excluding mulch packages that have become saturated with moisture.
  • Avoiding excessive handling of the product or test measure by rocking, shaking, or tamping it during the test procedure.

NIST OWM also provides an “on-demand” webinar for “Mulch and Soils Labeled by Volume”.  The webinar is 1.5 hours in total length and contains individual learning modules, including video demonstrations. Since this is an on-demand webinar, no registration is required and can be viewed at any time via NIST OWM Laws and Regulations web resources.  Click on the link for the "How to Test Packages of Mulch and Soils Labeled by Volume", and then enter the password (NIST_2020) to view the on-demand webinars. 

You can choose to watch the complete webinar or individual modules, such as the method of sale or labeling requirements depending on your specific test equipment and test procedures training needs. The webinar includes the following modules:

  • Introduction and Demonstration of the Test Procedure for Mulch and Soils (11:26)
  • Method of Sale –NIST Handbook 130, Method of Sale (4:07)
  • Labeling Requirements –NIST Handbook 130, UPLR (24:14)
  • Test Equipment – NIST Handbook 133, Section 3.10. Mulch and Soils Labeled by Volume (10:10)
  • Test Procedure – NIST Handbook 133, Section 3.10. Mulch and Soils Labeled by Volume (29:30)
  • Evaluation of Test Results – NIST Handbook 133, Section 3.10. Mulch and Soils Labeled by Volume (5:37)

Please contact David Sefcik at david.sefcik [at] nist.gov or Lisa Warfield at lisa.warfield [at] nist.gov or at (301) 975-4004 or OWM [at] nist.gov  for additional assistance and information.

Released September 27, 2022, Updated September 30, 2022