Fallout 4 – Food Production & Assigning Settlers
According to the Wiki: A single settler assigned to harvesting food can work 6 food units worth of crops, whether they’re the standard 0.5 units per plant or mutfruit’s 1.0 unit per plant. This means that they can work 12 crops at . 5 each, or 6 at 1 unit each (or a mixture).