Cook the farro according to package directions. If using quick-cooking farro, this will only take about 10-12 minutes; for regular farro, closer to 40.
While farro is cooking, wrap each ear of corn in a damp paper towel and microwave on high for 3-4 minutes, until corn is mostly cooked but still a little crunchy. Allow to cool for a few minutes, then cut the kernels off of the cobs.
Whisk together the dressing ingredients. Set aside.
When farro is done cooking, drain and place in a large bowl. Allow to cool for a few minutes, then add the corn, blueberries, diced nectarine, and scallions. Toss to combine, then add the dressing. Taste and season with additional salt as needed. Serve cold or at room temperature.
Will keep in an airtight container in the refrigerator for up to 3 days.