OM246 measures living organic material too

Remember, the OM246 test measures the total organic material, living and dead.

If the grass has a more extensive root system, or a more extensive rhizome system, the OM value measured on an OM246 test will go up simply from there being more total organic material in the sample. I chose these images of a vigorous manilagrass sward because this grass can have an extensive rhizome system.¹ That manilagrass core makes a good photo to show this, but the same thing is happening with any grass species. The OM246 test is measuring living plant material if it is in the sample.

After I cut that core at 2 cm below the surface, this was the bottom of the 0–2 cm puck. I made a few marks in red to highlight some of the living organic material that is in the sample.

The inclusion of living plant material in OM246 test results means we don’t always want to be minimizing the test result. I think that’s obvious to most people—sand itself doesn’t hold together. We need plant material to hold the surface together. Letting the grass establish enough living material, without always punching holes in it and disrupting it, leads to firmer surfaces.

That’s why I recommend finding an OM level at which the greens perform as you like, and then adjust the work to try to keep the OM at about that level.²

Now for a bonus item.

Andrew McDaniel joined me to discuss his OM246 test results after eight seasons of testing. He and I have both learned a few things about turf management and OM246 dynamics by doing this test year after year. We recorded this short video to share a few thoughts about putting green management and soil testing.