lolwut? Seriously though, Redstone signals don't pass through nonsolid blocks like sugar cane. Use a BUD Switch or a timer.
aww... would it work on wheat? also, you could just use it for something else, like trees hooray for tree tubes! (its a large tree in a tube, it grows like that...)
Wheat is also transparent/nonsolid. But again you could use a BUD Switch, or just use a combination of deployers and a block breaker on a timer for a wheat farm. Trees might work. (By might, I mean a signal can pass through, but there is a Vanilla bug where current won't propagate because a block update isn't called. Also, it would be much easier to use some sort of timer system)
stick to forestry wheat farm. it might be huge, but it's not hard to set up. all it needs is the machines themselves the startup dirt the startup seeds
Forestry has a Sugar Cane Harvester dedicated for this purpose. To make it leak proof, use the following setup: Sugar Cane Harvester -> buildcraft pipe -> chest -> transposer/filter -> redpower tube -> item detector -> redpower tube -> chest The item detector should be placed in stuffed mode, which'll send a redpower signal if it can't place the items in the last chest, and should be connected in such way that the signal from the item detector stops everything that's before it.
except that they will keep costing you energy (), and they won't take stuff from chests. the buildcraft pipe was there to show you the connection point when using an wheat farm for example.
