OM doesn't last very long in *my* part of the world. The reason why may be a bit surprising. More on that in a bit.

I have my soils tested at least once a year, so I've been able to track the OM content over the past 30 years. Back when I first started, we rotated crops between alfalfa, cotton, and sudan-sorghum and our soils tended to run between 0.5% to 1%. Pretty low, huh? Now, that was with tillage and cultivation. That level is pretty much the norm for this area.

Then, 20 years ago I switched to grass seed and began practicing no-till. My OM rose to over 2%, almost 4% in some fields. Still pretty low by most standards, but incredibly high for *here*.

 An interesting fact emerged, or became visible, whichever, once I had been no-tilling for a few years...

Yep, termites.

My theory is, tillage buries residue. Termites are *always* present in West Texas soils, despite what some farmers think. Burying residue is loading their dinner tables with a year-round thanksgiving feast, so that the residue is depleted rapidly. Shifting to no-till forces the termites to forage above ground, exposing them to predators and weather, and thus slowing down the depletion of OM. Weather may play a part in OM breakdown elsewhere, but in the land of constant drought, it's those little varmints that play the biggest role.

And there ya have it... my honest opinion on what happens to residue *here*.