Dirt

"I don't really need to tell you where to find dirt, because you'll generally acquire stacks and stacks of it during the course of normal play. To stop it filling up your chests, consider using it to fill in terrain, rather than dig it out, when you want to flatten an area. Or make a farm out of it - growing anything from saplings to beetroot. Or just use it to convert the dirt shack you built to protect you from zombies on the first night into an enormous dirt palace with all mod cons."

- Duncan Geere

Dirt is a block found abundantly in most biomes under a layer of grass blocks at the top of the Overworld.

Obtaining
Dirt will drop as an item when broken with any tool or by hand, but a shovel is the fastest way to break it.

Natural generation
Dirt is found at any altitude, and comprises the majority of the upper terrain layers in most overworld biomes, bridging the gap between stone and grass blocks in various thicknesses.

There are approximately 1,850 dirt blocks per chunk in plains, forest, tundra, jungle, and extreme hills biomes. There can be as many as 3,000 in chunks with high mountains. Dirt generates in pockets underground as well. Dirt also generates naturally in the butcher's shop and in some houses in villages.

Dirt based blocks
When grass, mycelium, or podzol are broken using a tool that is not enchanted with Silk Touch, it will drop dirt. Grass paths will also drop dirt when broken, regardless of if the shovel has Silk Touch.

Farmland will drop dirt when broken. It will also turn into dirt if either a mob jumps on it, or if nothing is planted on it and it is not within four blocks of water.

Coarse dirt can be tilled to become dirt.

Usage
Dirt's primary use is for farming, but it can also be used as a highly available building block.

Farming
Dirt has the ability to grow saplings, sugar canes, and mushrooms, which can be planted directly in dirt under appropriate conditions.

Using a hoe on dirt will turn it into farmland, enabling wheat seeds, pumpkin seeds, melon seeds, potatoes, carrots and beetroot seeds to be planted on it.

Grass and mycelium spreading
When a dirt block is adjacent to a grass block and is exposed to a light level of at least 4, it will eventually be converted into a grass block at random intervals.

Mycelium spreads in similar fashion, but requires a light level of at least 9.

Data values
Dirt has only one possible tile name:, which it shares with podzol and coarse dirt. The block state defines which block is displayed.

Trivia

 * If dirt is tilled using a hoe and water is placed underneath it, the dirt will not cast a shadow on the water. Untilled dirt, however, will cast a shadow, this is likely a glitch.