Rinse rice in a sieve under cold water. Bring rice, water, and 1/2
teaspoon of salt to a boil in 1.5 - 2 qt heavy sauce pan, then reduce
heat to low and cook rice, covered until tender and most of the water
is absorbed (about 35 minutes). Let rice stand, covered, off the heat
for 10 minutes.
While rice is cooking, heat oil in a 12"; heavy nonstick skillet over
moderately high heat until hot but not smoking and saute scallions,
ginger, and sweet potato stirring until coated well (about 2 minutes).
Reduce heat to moderate and add remaining 1/4 teaspoon salt and pepper
to taste, then cook, covered, stirring occasionally, until potato is
just tender, about 12 minutes. Add rice and toss gently to combine.