Well I didn't want to slow anything down, I just wanted to make it so that you could build the farms, get the income bonuses from it, but not the population growth boost.

Actually what I did was normalize the farm bonus so that you basically always have the same level of bonus as you would normally start with. The benefit is that it effectively caps your city populations around 380000, where they're still very managable in terms of unrest and squalor.