But beyond the familiar mantras about nutrition or reduced fossil fuel use, the movement toward
 local foodis creating a vibrant new economic laboratory for American agriculture. The result, with its growing army of small-scale local farmers, is as much about dollars as dinner: a reworking of old models about how food gets sold and farms get financed, and who gets dirt under their fingernails doing the work.SEATTLE — The cultivated rusticity of a farmers’ market, where dirt-dusted beets are status symbols and earnest entrepreneurs preside over chunks of cheese, is a part of weekend life in cities across the nation as the high days of the summer harvest approach.