I've done a bit of looking on wikis and the best I can find is that crops don't grow on all types of dirt, but I haven't been able to find any kind of dirt that can grow crops. I want my Glitch to be a vegetarian but I keep starving to death.
Are you using a hoe to till the land first? You have to gather some wood and some cobblestone to make a stone hoe, then till the dirt and plant your seeds in it in order to create a farm. Plain Ol' Dirt won't cut it.