Refers to the short stalks left in a field after crops such as rice or wheat have been harvested.
田んぼには刈り根だけが残っていた。
Only stubble remained in the rice field.
Compound of 刈り (kari, 'cutting, mowing') + 根 (ne, 'root'). The exact historical derivation is uncertain, but the spelling is conventionally associated with the meaning 'stubble'.