A lime-requirement buffer built for the low-buffering, sandy Coastal Plain soils of the Southeast — used by several Southern land-grant labs.
The Adams-Evans buffer was developed specifically for sandy, low-organic-matter soils that don't hold much reserve acidity. On those soils, stronger buffers (like SMP) overestimate lime need; Adams-Evans is calibrated to give a gentler, more accurate recommendation.
It's the classic method for much of the Coastal Plain. Some states have since moved to newer methods — Georgia, for example, retired Adams-Evans in favor of a direct Ca(OH)₂ titration — which is exactly why the method that's correct for your soil depends on your state's current publication.
Related: Buffer pH · Sikora buffer · Lime requirement