I usually build Communal Farming after the Land Clearance, it only costs 1200F, but Crop Rotation is too expensive to get early on at 2400F. I usually get it mid-game, but never really get Irrigation.

Also I disagree about the mines, places like Vienna get around +1100 from a Mining Complex, if it costs 3500F to build then you're making that back in 7 turns (considering you already had around +550). Then you'll be getting big profits...