Last post I showed how you could use the new Observer block to create a wheat/potato/carrot farm that automates everything but the planting. I use a Dispenser with a water bucket to break all the wheat plants, but that still leaves the gathering of the wheat and seeds that are left on the ground by the water. This I do via a Hopper Cart system directly under the farmland. Here’s how you make one.
First we need a place for the Hopper Cart to rest. When not in use, it sits on an unpowered piece of Powered Rail that itself sits on a Hopper. That Hopper will pull items that the Hopper Cart gathers and send them into a chest or item sorting system. In our wheat farm from last post, the maturing of the wheat triggered a second redstone signal that split in two. One line went to the Dispenser with the water bucket. The other went to the Hopper Cart gathering system.
There are different ways to lay out the track, but I find that the easiest is just a spiral that ends at a block and some Powered Rail. When the Hopper Cart is stopped by the block, the Powered Rail will send it back in the other direction until it arrives back home. Laid out like this, the Hopper Cart actually passes under the entire farm twice, dramatically increasing the chances that it will pick up everything.
One last thing: I find that items in corners sometimes get missed if the rail makes a simple spiral directly under the farmland. To fix this problem, I add an extra couple of blocks and tracks at the three corners that are not the Hopper Cart’s home. With this, I have so far had a 100% success rate at gathering items broken by the water Dispenser.
It is also important to note that you won’t want to surround your farm with fences unless you decide to place a line of track directly under the fence line, as well (in which case you might not need the little extended corner areas with Polished Granite in the above screenshot). If your track is only under the farmland, items that are pushed onto the blocks with the fence posts will not be picked up. This is part of the reason why my 9×9 farm from the last post was surrounded not by fence posts but by hedges (Oak Leaves blocks).