Minecraft wiki entry for Crop_farming, associated text: These crops can only be planted on farmland, which is produced by using a hoe on dirt or grass blocks. If there is no water nearby, farmland dries out and reverts to dirt, but only if there is no crop yet planted on it. The water can be a "still" source block, or flowing, but either needs to be within four blocks of the farmland horizontally, on the same vertical level or one level above. If farmland becomes completely dry and a crop is planted on it, the farmland does not revert to dirt. Thus, it is possible to grow crops without water (say, in the Nether) by hoeing the dirt and immediately planting a crop. The farmland does not revert until after the crop is harvested, and even so that can generally be avoided by immediately replanting. Note, however, that this "dry farming" makes crops grow slowly.