Simple .esp mod that changes all buildable settlement farming plants to give the same yield as Mutfruit (1 food value per plant). Does not change the Graygarden planters to give double yield currently.

Just add to the data folder and enable through Nexus Mod Manager
http://www.nexusmods.com/fallout4/mods/modmanager/?

This mod alters the default forms so removing or turning off the mod will revert values back to their original values.

Note: Settlers may need to be re-assigned after adding the mod, and may result in more idle farmers if you already had a reasonably high food value. The amount that each settler can gather is still capped at 6 food, this just allows you to reach those caps with fewer plants or without subsisting solely on mutfruit.