minecraft-java-edition
I've just made a mobspawner trap in my world after updating to 1.6.1, after the world (and chunk with the spawner) was created a while ago maybe in 1.2/1.3? In either case, the world was spawned before zombies dropped iron, potatoes and carrots.
Does this mean my mobspawner trap is never going to drop anything but rotten flesh? Or do I need to leave it longer?
Most mob farming techniques use a stream of water which collect all the monsters in the room to a central point, and then drowns them by pulling them underwater. Some other ways to kill them are:
Just as a note, most people just build enormous completely dark rooms (like this one) to farm mobs rather than using the actual mob spawner blocks.
Here are some screenshots from the link above:
If you are using WorldEdit you must have Bukkit installed. If so install this plugin
With this, you'll be able to change the spawn to whatever you like.
UPDATE
I've found exactly what you're looking for here
You can craft mob spawners with ingredient, you just have to download Mod Loader and put some class in the .minecraft/mods folder. You should find instructions on his page. And yes it's for single player
Best Answer
Items dropped from mobs killed from a Spawner have nothing to do with the Spawner itself. The Spawner only spawns the mob, it does not determine what the mob will drop when killed. A skeleton Spawner back from when spawners were first added into the game would still drop enchanted bows if the save was updated to the current version of Minecraft.