Over 20 years ago I worked for a soil testing laboratory in Phoenix, Arizona. I sampled agricultural and golf course soils, and organic matter testing was performed on most samples. Sample depth varied on putting greens depending on root depth. Samples arriving at the lab were dried and sieved to remove living organic matter; because after all, soil organic matter was defined in the scientific literature (Gaussoin et al., 2013) as “recognizable and unrecognizable grass-plant materials in various stages of decay, microbial biomass, small fauna, the by-products of plant growth and decay, and other components.” Basically, all the “dead” stuff in the soil. Results were perhaps useful if collected by the same person and tested at the same lab for each golf course, but values were not transferable from one course to another because different sampling and analysis methods were used in each case. With that in mind, I didn’t pay much attention to the organic matter results, and certainly found no use for them when making recommendations for managing putting green organic matter levels.
Now, after four years of research by the “Organic Matter Brain Trust,” a group of scientists from four different universities and USGA agronomists, we are ready to take a consistent method of organic matter testing mainstream. Collectively, the group has created a consistent set of sampling and analysis recommendations, all for one and one for all. USGA agronomists have sampled over 300 putting greens over the past four growing seasons and have been able to build a strong database for courses to compare organic values. The biggest difference between this new method and more traditional ones is we recommend collecting a sample 2 cm deep and leaving the turf (verdure) intact to capture total surface organic matter. You can find a full summary of the recommendations in the USGA article “A Standard Method for Measuring Putting Green Surface Organic Matter."
So, why is this new method important? By using a consistent sampling and analysis method, course superintendents and agronomic consultants can compare values across courses. They can also track organic matter levels year after year with confidence that the results are accurate, repeatable and comparable. This information is extremely beneficial for making organic matter management choices like aeration frequency and tine size, sand topdressing application amount and frequency, and nitrogen application rates. To take a deeper dive into this topic, read the USGA article “Cracking the Code on Putting Green Organic Matter.”
If you want to start using this new method, reach out to your regional USGA agronomist for help with the sampling process and to get information from our growing surface organic matter database that can be used to guide management decisions. If you prefer to collect samples on your own, there are 10 laboratories listed below that participate in the USGA Putting Green Laboratory Accreditation Program (PUG) | A2LA. Not all these labs use the new methodology, so be sure to discuss the process with them. In addition, the University of Wisconsin Soil and Forage Lab can perform this test.
Tifton Soil Testing Lab, Georgia
Turf and Soil Diagnostics, Kansas and New York
Hutcheson Sand and Mixes, Canada
European Turfgrass Lab, United Kingdom
Sports Turf Research Institute, United Kingdom
Sports Surface Laboratory, United Kingdom
Reference
Gaussoin, R.E., Berndt, W.L., Dockrell, C.A. & Drijber, R.A. (2013). Characterization, development, and management of organic matter in turfgrass systems. (eds J.C. Stier, B.P. Horgan & S.A. Bonos). Turfgrass: Biology, Use, and Management, 56, 425-456.
https://doi.org/10.2134/agronmonogr56.c12
West Region Agronomists:
Brian Whitlark, regional director – bwhitlark@usga.org
Cory Isom, agronomist – cisom@usga.org