In this GitHub issue it came to light about a change made last year regarding wheat as a resource. In vanilla plains give +1, add on the wheat resource and even when unimproved this now yields +2. It was deemed as excessive and the initial unimproved yield was set to 0 and the improved went to +2. I think this needs to be reversed to bring back the vanilla values, for this reason. Grasslands as an unimproved tile yields +2 compared to plains with wheat which only yields +1. What is the difference? Wheat, or indeed any of the grains, is only a specific type of grass cultivated to yield a better harvest than ordinary grass. All farming does is improve again the output of the already better grass: wheat. This is the original Civfanatics discussion about wheat.