"the portrait of a black pea-picker who followed the fruit crop is a clear testimony to Lang's closer relationship to subjects in the field than to those on the street."
I think the sentence isn't really well written enough to definitively say. It seems it could be literal in that the picker actually follows the crops as they ripen so that he can pick them, but it also could mean that he keeps up to date on the harvest and knows how much fruit the crops have given. I don't think that the last part of the sentence sheds enough light on the matter. Surely there mu