Temperature for loss on ignition in turfgrass soils

I’ve been thinking about measuring organic matter and about the quantity of sand required as topdressing for any turfgrass surface.

For samples taken near the turfgrass surface, I would like to measure the mass loss on ignition, and call that the total organic matter. I don’t want to screen the sample to remove any of the undecayed material.

Of course, one must ignite the sample at a specified temperature. Last year, I had some samples sent to Brookside Laboratories, asked for them to be held until my arrival, and then I checked the samples before they went into the muffle furnace, and again after they came out.

Five soil plugs at a 0 to 20 mm depth below the surface from a korai (*Zoysia matrella*) golf course putting green were burned in a muffle furnace at 360 and 440 °C. These photos show the charred residue remaining after a 360 °C burn, and the complete ashing after a 440 °C burn.
Five soil plugs at a 0 to 20 mm depth below the surface from a korai (Zoysia matrella) golf course putting green were burned in a muffle furnace at 360 and 440 °C. These photos show the charred residue remaining after a 360 °C burn, and the complete ashing after a 440 °C burn.

I like to run these samples at 440 °C in the muffle furnace, because that produces a complete ashing of the organic material. In the samples above, the organic matter content was about 15%, or 150 g of mass lost after the burn in the muffle furnace from 1 kg of material.

You may notice that the verdure—the aboveground plant material that remains after mowing—was left on the samples in the photos above. I prefer leaving the verdure on putting green samples. I’ll explain why in a forthcoming post.

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