New OM246 video script

I prepared a new video about OM246. This video premiered at the Ontario Turfgrass Symposium last week, and it’s now available for worldwide viewing.

I wasn’t able to get to Ontario for this event, but I was glad to have the opportunity to explain why OM246 testing is done, how it works, and what one can do with the results.

I started with an intro clip from a campground in southern Thailand. Then I wrote the script below, recorded it discreetly in a lounge at Narita Airport before a flight, and added the video clips of lab procedures, test results, and display of the test data, over the top of that soundtrack.

I hope you’ll watch the video and find it informative. Even if you’ve been doing this test for a few years, I expect you’ll learn or be reminded of some new things related to OM246 total organic material testing.

Here’s the script.

Before the FOUR parts of the OM246 testing process, why are we doing this test?

The purpose is to check, with an accurate test, the organic material amount at the top of the turfgrass rootzone. By checking the organic material over time—I recommend annual checking—you can find out if the amount of sand added and/or organic material removed is enough to keep the rootzone consistent, or you may find that you need to do more, or you may discover that you can do less. Once you know how fast the organic material is accumulating, and how much sand is required to produce the type of conditions you want, you can adjust the work to make playing conditions even better, for more days in the year.

I call this total organic material by depth, because the OM246 testing checks the total organic material at specific depths in the rootzone.

The first part is sampling.

We take soil cores, or soil profiles, and cut them at specific depths—at 2, 4, and 6 centimeters below the soil surface. Keep in mind that the lab will burn all of the sample, so you are looking to collect from 30 up to about 150 cubic centimeters of material for each depth.

I recommend taking five subsamples from each green tested. I recommend testing at least three greens each time you sample. For an 18 hole golf course, I like to test three greens at each depth: 0–2, 2–4, and 4–6 cm. I like to test an additional three greens at the 0–2 cm depth only.

There’s actually quite a bit of variability in total organic material right at the surface of the green. If the average OM2 on a green is 6%, and if you take only one subsample, that could test at 3.9%, at 4.7%, or at 8.3%. We can’t measure the entire green—that would require a sodcutter. What we can do is take multiple subsamples from a green, and average them.

For a typical green, combining 5 subsamples is going to get us close to the overall average. After we’ve done that sampling method on multiple greens–five subsamples per green, on at least 3 greens—I’m confident that the average OM2 value is accurate and is suitable as a decision making criterion.

The SECOND part of the testing process is laboratory analysis. There are TWO distinctive parts of the OM246 testing method that I want to highlight.

First, the laboratory measures the organic material on 100% of the sample. You are probably already aware that soil organic matter is measured on soil that has passed through a 2 mm screen. Anything that doesn’t pass the screen gets discarded. That means roots, thatch, mat, rhizomes—those don’t get measured on a standard soil organic matter test. Second, the OM246 sample is measured in its entirety. Soil organic matter, on the other hand, is measured in tiny 2 g scoops, taking a sample from the material that was sent to the lab. When trying to measure thatch and mat and sand from the top of the rootzone, you have to measure all of it. Its not possible to scoop a representative mix of thatch and sand once they are dried and crushed.

The Beauty of OM246 is there are no screens and no scoops, and no thatch that gets discarded. It’s all getting measured.

The sample is burned until all the organic material turns to ash, and the mass lost through burning is called the “total organic material” of the sample. The sand and soil stays the same mass—it doesn’t burn— but the organic material burns away to a white ash at 440 degrees Celsius in the muffle furnace.

The third part of the OM246 test is interpretation of the results. Now that we have the total organic material numbers, we will try to figure out what they mean. To do this, I find it useful to look at a few things, and I show the results this way on the reports I send to clients.

First I show how the total organic material has changed over time. Is it staying the same, increasing, or going down? I also show how the total organic material compares to other greens of the same species. Although we won’t make decisions simply by comparing to other greens, it is useful to know how one’s greens compare—are they lower or higher than usual? A third thing I look at is consistency from green to green. Is one green at 10% and another at 17%? Or are all the greens clustered around the same value? It’s useful to consider the within course variability.

Now we’ve identified a few things: how the organic material is changing over time, how it compares to other greens of the same species, and how it varies between greens on the same property.

Based on these results, it’s time to make recommendations. This is how I do that.

I start by looking at a few data points. How much sand has been applied? What amount of core removal, sand injection, or scarifying has been done? How much N was applied, and how much did the grass grow?

From these three things—sand, OM, and growth—the work can be adjusted to produce better surfaces in the future.

If the surfaces have just the right firmness level and hold the right amount of water, then I want the total organic matter to stay the same over time, and I can adjust the sand topdressing and other organic matter management work accordingly.

If the surfaces are too soft, or hold too much water near the surface, and I would like them to be firmer in the future, then I want to see the total organic matter decrease over time, and I will increase the amount of sand topdressing and organic matter management.

If the surfaces are too firm, or don’t hold enough water near the surface, and I would like them to be softer in the future, then I want to see the total organic matter increase over time. To do that, I will reduce the amount of sand topdressing and organic matter management.

Here’s how not to do it—don’t chase after an OM number in the soil that is disconnected from the surface performance of your greens.

I’ve learned a few other things, and I’ll wrap up with these.

Healthy grass, or a better growing environment, and you tend to have higher OM values.

When you don’t topdress, and when you don’t core, the organic material doesn’t change much, so long as you keep the growth under control.

I’ve got an OM246 calculator that I recommend you check out to get an idea of your OM accumulation rate.

We are doing this test to keep OM under control. Doing the OM246 test, you find out quickly if you are applying enough sand, not enough sand, just the right amount, and also you learn just where in the soil that sand needs to go.

One more thing—you can also check the particle size distribution of the OM246 sand after the organic material is burned off. This extra test is useful to check the type of sand at the top of the rootzone, and how that material compares with the original rootzone material and with the topdressing sand. If you want to make changes in the rootzone, you can check not only how the organic matter is changing, but also how the sand gradation is changing.

If you’d like to learn more about this type of testing, you’ll find all kinds of information at the ATC website.