Stones are a big problem to anyone planning to harvest root crops with power equipment, even with the simplest blade that lifts the crop, because forceful contact with stones will bruise vegetable skins and adversely affect storage life. In stony soil, be sure to gently hand-harvest your root crops with a spading fork or potato hook. But stones have a good side, too. They help drainage to varying degrees as water finds its way down, along, and around them. Even a tight clay soil with stones in it will leak water past them better than if it had no stones.
Stones also warm up faster than soil and release their heat slowly.
They help soil warm up faster in the spring, contributing to a longer growing season. My husband and I argue about the best way to harvest asparagus. He claims that it should be snapped off wherever the stalk yields to pressure. I think it should be cut with a knife. We hate to take sides, but when we go out to gather asparagus, we take along a sharp knife and cut the stalks off at the base.