Many tree companies have stump removers that saw below the soil line. The old soil line, that once stumped you ,can now have a sense of humus. The most thorough job is an extraction with a bulldozer. Todd, Waterford, CT Any plant benefits with elevated rows , especially vine type plants. Rows make it easier to cultivate and keep weeds at a minimum.
Weeds attract insects.
It is far easier to harvests in rows. Ipomoea batatas is more easily grown in zone 6 in the past years but still risky. They like warm sandy soil. Use a low nitrogen fertilizer. A good variety for Connecticut is Big Stem Jersey.