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Many golf courses aspire to have great putting greens, but the road to success can be dimly lit and poorly marked. Achieving great putting green conditions for an important event might be within reach, but what about month after month and season after season? Excellence over a long period of time requires identifying desired standards and the inputs necessary to achieve them. Inevitably, the topic of managing organic matter in the upper rootzone must be confronted.

Organic matter management and its measurement brings forth a wide range of questions. How much is too much? What role does it really play in putting green quality? Can I reduce organic matter content without too much disruption? Should I reduce it? There are varying points of view on these and other questions related to the topic, but what the industry should not disagree about is the need for a standard method to test organic matter. Right now, we have different approaches that yield different results, which makes it hard to understand what any particular number means in the grand scheme of things. A superintendent can track organic matter content over time in their own greens, but how do those numbers compare to other courses in the area, or courses with similar greens around the country? Are the numbers too high, too low, or just right? We don’t have good answers because there is no standardization in testing.

The purpose of this article is to provide an update on work that the USGA Green Section and turfgrass researchers are leading to develop a standardized approach to sampling and testing that will allow us to crack the code on putting green organic matter measurement and management. Soil labs and superintendents are playing a significant role in this endeavor also. Our goal is to lay the foundation for individual golf courses to produce excellent putting greens that meet the facility’s standards as efficiently as possible.

Up front, it is important to be clear about the vocabulary we are using. In this article, organic matter refers to the total organic matter in the upper rootzone including the grass on the surface and any living or decaying leaves, roots, shoots, rhizomes and stolons. The term “test” refers not only to the procedure in the soil testing lab but the process used to take samples at the golf course.

Why is standardized testing beneficial?

What is the point of developing a standardized test for organic matter? This is a great question and if a significant effort in testing standardization is to continue, there should be clarity on what problem(s) will be solved. This work will build a foundation for future research into the optimal range of organic matter for golf course putting greens and the role of organic matter in putting green firmness. Creating effective management strategies is much more difficult without a standard testing method. Research can lead to amazing breakthroughs, but the ability to further advance the work of earlier scientists will be hindered with non-standardized organic matter testing.

Second, a standardized test will create a common language for superintendents to use. In the current environment, discussions about organic matter are fragmented along the lines of different testing methodologies. Much as soil moisture meters allowed superintendents to communicate more clearly both within their teams and among colleagues, we expect the same to happen with organic matter testing standardization. Superintendents will have a point of reference for making data-driven decisions on aeration, topdressing and fertilization programs, and they will be able to share knowledge with their colleagues to improve understanding and results across the industry.

Finally, there will be an opportunity to create a more robust dataset of organic matter measurements across putting green age, grass species, geographic location and other variables. This will more accurately describe what exists in the field and allow superintendents to evaluate their current situation and fine-tune their cultural practices accordingly.

What is the current state of organic matter testing?

Numerous tests are available to measure organic matter in soils and they vary in procedure, complexity, expense and time to conduct. They were developed at different times in different industries for different uses. Additionally, there are even more ways to take samples and prepare them for a test. With so many variables involved, it is not surprising that there is no common language for superintendents and researchers to use.

Where are we going?

With funding from the USGA’s Mike Davis Program for Advancing Golf Course Management, we convened Dr. Doug Soldat from the University of Wisconsin, Dr. Jim Murphy from Rutgers University, Dr. Roch Gaussoin from the University of Nebraska and Dr. Doug Linde from Delaware Valley University to conduct a literature review on organic matter testing in putting greens. They identified numerous testing methodologies which all had their own strengths and weaknesses and found the loss on ignition method to be the most promising if a standardized test were to be developed. However, consensus still needs to be established in the following areas:

How to sample a putting green: Spatial variability of putting green organic matter can be considerable, so determining the right number of samples to take per location, sample depths and whether to include the verdure (turf canopy) in the sample or not are key questions.

Collecting and shipping the samples: What type of tool should be used to take samples and how should they be shipped?

Preparing samples in the laboratory: Many labs use a grinder and sieve on the samples, but this process has an impact on the results. For example, by removing larger pieces of organic matter, the sieve process can skew the numbers lower than they are in reality and remove some of the organic matter that superintendents are most concerned about managing.

Lab testing procedures: What should the standard protocols be for the loss on ignition testing? Key considerations here are furnace temperature and the amount of time each sample spends in the furnace.

The above-mentioned group of turfgrass scientists is working with USGA agronomists on finishing recommendations for a standardized putting green organic matter testing method that is expected to be released in the first quarter of 2024. In the longer term, it is our hope that an ASTM standard is established to be used by turfgrass researchers and testing labs for the benefit of superintendents and turf managers everywhere. For a very informative update on the standardization process from one of the researchers involved, listen to the USGA Green Section Podcast episode featuring Dr. Roch Gaussoin from the University of Nebraska, Lincoln.

The future and your role

For all the interest and enthusiasm about establishing an industry-adopted standardized test for organic matter, the information you get is still only descriptive. It assigns a number to the organic matter quantity on the day the sample is taken. Used year over year, testing evaluates the effectiveness of the organic matter management program. In other words, a superintendent will learn how organic matter content changed over time under their management program.

This descriptive aspect of the test has value, but the biggest breakthroughs in turf health, playing quality and golfer experience will come from using both on-site tests and a database of organic matter content and trends from many courses as a prescriptive tool to achieve the standard desired and optimize inputs. This is where golf course superintendents will play a key role in cracking the code for organic matter management – by using a standardized method and sharing information. This is an important point to consider and is worth elaborating in more detail. Think of the possibilities!

With a standardized test and a database sortable by geography, grass species, putting green age and many other variables, an individual golf course can see where they fit. Are the greens high in organic matter, medium or low? Turfgrass researchers will be able to expedite questions around the interaction of topdressing, core aeration and fertilization on organic matter levels and surface firmness. Rapid advancements can be made with projects duplicated in many locations and results reported in a common language. Golf courses contemplating new putting greens will know what they are getting into in terms of organic matter management over the life of their greens. Wouldn’t it be disappointing to find that after five years turf health and surface conditions were substandard due to the lack of information about the best course of action in managing organic matter?

Many golf courses today want to improve surface firmness and turf health and are attempting to do so through different aeration and topdressing strategies. In many cases, they are an “experiment of one” because the industry doesn’t have a standardized test for organic matter. This makes it hard for superintendents to document their progress or understand where they’re trying to go.

Footnotes on the journey ahead

Some will disagree that a standardized test is needed and prefer the status quo. Others will find fault with the standard developed. Ways will be identified to make the test better. Some will find that using the test as the basis for a prescriptive tool is complicated and will give up. New research questions will emerge as current questions are answered. These are all occupational hazards that arise when new paths are pursued, but there are gains to be made.

Here is word of encouragement for those who persevere. The USGA Green Section has been committed for more than 100 years to providing golf facilities with resources and tools to produce better turf for better golf. These are the same motivations that led to the development and continual refinement of the USGA Recommendations for a Method of Putting Green Construction. Convening a group of scientists to develop a standardized organic matter test is just one way the USGA is helping courses improve their putting green management. We also provide superintendents with an affordable way to track, analyze and manage the resources used to maintain their putting greens through the DEACON platform. We developed the GS3 ball to provide superintendents with a way to measure putting green speed, firmness, trueness and smoothness with one tool.

The next few years are sure to be an exciting time for putting green management as we build a better understanding of putting green organic matter dynamics and how they can be altered. Most importantly, developing a standardized test will only fuel the wisdom of superintendents who will skillfully apply the information learned at the right time in the right way. The road may not always be smooth, but working together to crack the code on putting green organic matter will fill most of the potholes and add brightness to the path ahead.