I’ve been trying to explain what’s normal, and in one of those explanations I ended up making these charts.
I also separate those same data by species.
In ATC’s report for OM246 tests (see a sample report with charts), I include charts and percentiles that show what is normal for the current test results, based on the most recently updated version of the dataset.
If you want a take-home message from seeing that OM2 can vary from one course having less than 4% and courses filling up the range in between all the way up to more than 16%, I will reiterate that I find this most useful as a way to assess the effect of the maintenance work by checking the change in total organic material over time. I explained this in one simple trick to transform putting greens from usually good to consistently great. That is, I can have great greens at OM2 of 5%, 8%, and 12%. That’s something that depends on the specific course. But within a specific course, looking at change over time is remarkably informative about the effects of the maintenance practices and the growing conditions between sampling events.