Maybe it’s just me, but I find managing my Farms very difficult with the African factions in the late game. It is very micro intensive to change the balance in the number of Farms producing a given resource without switching all of them at the same time every time or selecting all on the screen, which is usually more than you want.
My suggestion is to create a tie between a Granary and the Farms built within its boost radius that allows the player to switch all the Farms connected to it from an option available at that Granary.
Making the Farms and the Granary a bit smaller would also make life easier, but perhaps being that big is simply part of the design as a trade-off for their flexibility, like the Hacienda.