Beans fix their own nitrogen, which if you like to companion plant (and some people do), the beans don't compete for the nitrogen. Some studies indicate the the beans assist (perk) the other plants by giving them nitrogen WITHOUT over supplying nitrogen - and too much nitrogen can be a problem for some plants (corn in particular). The standard North American Indian Three sisters planting is: Corn, beans and squash. This combination dates back ........ probably centuries and it has been around a long time for good reason: Corn is actually fairly WEAK rooted when young; corn can uprooted fairly easily when it starts growing. Squash on the other hand is a rooting power house. The squash stabilizes the corn. The squash with it's large leaves ALSO shades the soil (all plants that I know of like shaded soil, keeping their roots cooler -- even full sun plants want shaded soil). The beans then scamper up the corn, and perk the corn and squash with nitrogen. What your asking is can I take this classic all time threesome and substitute sweet potatoes for the squash. I really can't see a reason why you could not. It sounds reasonable. Further more Blistering on sweet potatoes can be prevented by adding Borax to soil - and corn loves boron (boron gives corn not only better tassels but better yields). Additionally, both corn and sweet potatoes need and love potassium. So when I think about it... it sounds like a really good combination. Best of Luck.

- Celeste Archer