What's with the terrace farming?

[Greasy Dave]

CAn anyone explain why terrace farms on similar hills give different yields. PLains or grass- I've got one farm on a grass hill giving 4 food and 2 hammers, and others giving only 2 food and 2 hammers. Similary on plains hills, 3 food, 2 hammers or 2 food 2 hammers? I've even got one grass hill that only gives one food and one gold?

I have to admit, I haven't double checked it ni the city screen. But I'm fairly sure it's not a graphics glitch because before I built the terrace farms the worker window told me how much food each farm would give - 4, 3 or 2. There seems to be know logic to it.

 

[noncognosco]

Terrace farms give one food plus one for each adjacent mountain tile. Grass or plains does not make a difference.