Surface organic matter measurement for putting greens

By Doug Soldat, University of Wisconsin-Madison

Winter environmental conditions are influenced by the weather, ground cover (particularly snow cover), and soil conditions. We still have quite a bit to learn about the winter conditions that make putting greens most susceptible to winter damage, but the WinterTurf sensor team and the many golf course superintendents participating in our sensing project are helping to figure that out. The WinterTurf winter sensors record soil temperature, soil moisture, carbon dioxide, and oxygen levels every 15 minutes. From these millions of data points, we hope to be able to better predict when winter stress may occur and therefore be better able to reduce the risk of winter damage.

While we can’t control the weather, and snow cover can be difficult to manage, we are able to move the needle on some soil properties. Soil organic matter is one property that plays a big role in soil temperature, soil moisture, and likely soil gasses as well. Therefore, soil organic matter management may also play a key role in preventing winter stresses. Until recently, no standard for measuring surface organic matter existed. In 2024, the United States Golf Association unveiled a recommendation to measure and track surface organic matter of putting greens. Below is a brief outline of the method, which will help putting green managers understand the impact that their management (fertilization, topdressing, aeration, etc.) is having on their surface organic matter. 

1. Collect about 10 standard-sized cores (Fig. 1) from each putting green you want to test. The cores should be about 30 feet from each other. Surface organic matter fluctuates during the season, so collect samples at the same time each season, and at the same time with respect to annual cultivation events (i.e. every September prior to fall aeration).
2. Using a sharp knife, cut the cores to a depth of either 2 cm or 1 inch. Leave the grass on the sample.
3. Ship the samples to a laboratory that offers the USGA surface organic matter test. There are a growing number of laboratories that offer this test. This test will estimate surface organic matter using loss on ignition at 440C (not the usual 360 C) for 2 hours. The laboratory should not grind or sieve the submitted samples prior to ignition.
4. Track surface organic matter trends across a period of time. As our knowledge advances, specific recommendations for surface organic matter levels that minimize the risk of winter stress damage may be developed. Topdressing and aeration practices can be manipulated to change surface organic matter, if warranted.  

As the adage goes, you can’t manage what you don’t measure. Surface organic matter plays an important role in the performance of putting greens and may influence winter stress. To be best prepared to capitalize on new knowledge as it develops, you should consider tracking your surface organic matter now.