barren land
埣 centers on land that is unproductive and empty: barren, infertile ground.
埣 combines 土 (earth, soil) with 卒, which likely contributes the sound. The exact historical development is uncertain, but the character is used for barren land.
The soil radical 土 beside 卒 suggests earth that is finished or used up, like land that has become barren.
For ソツ, imagine a barren plot of land where a soldier (卒, ソツ) once stood, leaving the ground empty: soldier -> ソツ.