OM246

A colleague from Canada wrote to me with five comments after finishing this ATC Office Hours with Chris Tritabaugh (or listen as a podcast here). Just listened to your talk with Chris and wish I had the where about to attend it live, as I would have kept the chat room real busy!

Joe Gulotti, host of The Talking Greenkeeper podcast, invited Jason Haines and I to join him for a fun conversation. We talked about sustainability, MLSN, OM246, playability, sand topdressing, and a special Christmas for Joe in Arizona.

Daniel Hahn asked an interesting question about organic matter. Talking about “variability between greens at the same site,” he wondered, “could you explain what your opinion is about the statement, if you think greens vary a lot in OM or if you see minor difference?

Chris Tritabaugh and I met to review the OM246 test results from samples collected in October 2021 at Hazeltine National Golf Club. We did this as a livestream episode of ATC Office Hours, which is available for watching or listening at your leisure.

Soil organic matter, and the total organic material measured by OM246 tests, are reported on a mass basis. That is, mass of organic matter per mass of soil. For convenience, this is usually reported as a percentage (%).

One of the things I’ve started looking at when doing OM246 reports is the combined OM in the top 6 cm (2.4 inches) of the rootzone. This shows the big picture of total organic material change at the surface of the rootzone.

I’ve written a lot about OM246 testing for total organic material by depth in the soil, and why I think this test is so useful. Something I hadn’t written, until this week, is my own set of sampling instructions.

Organic material measurement by mass loss on ignition is reported on a mass basis. For OM246 testing, I prefer doing a burn at 440 °C.1 The equation for loss on ignition (LOI) as a percentage takes the mass of sample dried at 105 °C ($m_{105}$), subtracts the mass of the sample after burning at 440 °C ($m_{440}$), divides by the original mass, and multiplies that by 100.

I’ve made some updates to the standard OM246 report this year. The portion of the report with charts is showing four distinct things, and I showed examples and explained them in this video.

I like to test the total organic material at the surface of a turfgrass rootzone in autumn. Doing the testing in autumn captures the majority of the growth, accumulation, decomposition, removal, and dilution that has happened during the previous year.