Call me nitpicky, but I'm not really too enthusiastic about Gallifreyan Dirt.

It acts nothing like vanilla dirt.

Vanilla Grass Blocks can

1. spread grass
2. be made into farmland
3. decay the grass in certain conditions
4. be made into a coarse variant
5. only gained when using a silk pick, otherwise dropping the dirt variant
6. has a snowy variant

The Gallifreyan Dirt does NONE of the above, and I feel that this should be changed.

Blocks:

• 
  Coarse Gallifreyan Dirt

Crafting Recipe: 2 Gallifreyan Dirt and 2 gravel yield Gallifreyan Coarse Dirt

Behavior: 

• Under the right conditions, the following can be planted in Gallifreyan Coarse Dirt:
  • Saplings
  • Mushrooms
  • sugarcane
• Gallifreyan Coarse Dirt will Become Gallifreyan Dirt When Tilled
• Gallifreyan Grass will not spread onto Gallifreyan Coarse Dirt
  
  
  
  
• 
  Gallifreyan Farmland Block
  

How to get it: Can only be gained via commands. It's unobtainable in creative and when mined with a silk pick, it will just drop Gallifreyan Dirt 

Behavior: 

• Players may plant seeds in Gallifreyan Farmland Blocks 

Hydration:

A farmland block will be created dry. It will become hydrated if the following conditions are met:

1. Water up to four blocks away horizontally, including diagonals.
2. The water must be on the same level or 1 block above farmland block level.

The blocks between the farmland block and the water make no difference.

There is nothing the player can do to affect the rate at which farmland becomes hydrated. Each farmland block within a 9x9 grid of farmland with a single water block in the middle has exactly the same chance of becoming hydrated as a single farmland block in an ocean.

Farmland can also be hydrated by rain.

Different types of seeds grow faster on hydrated farmland than on dry farmland. Hydrated farmland will yield a fully developed wheat crop in a little over a single day/night cycle.

Decay:

Under certain conditions, a farmland block will "decay" becoming a dirt block, regardless of its state of hydration. This will happen if any of the following occur:

If the farmland block is dehydrated and nothing is planted on it for too long.

If the player or any mob jumps/falls on the block (with a greater chance as falling speed increases).

In 1.9,[upcoming] mobs smaller than 0.512 cubic block cannot destroy farmland. This includes rabbits, chickens, bats, ocelots, wolves, cave spiders, endermites, silverfish, baby mobs, small slimes, and small magma cubes.

If a piston arm is extended over a farmland block.

If a piston pushes a farmland block down.

If a solid block covers the top surface of the farmland block such as when pumpkin or melon blocks appear.

If an Enderman teleports directly on top of a farmland block.

When farmland decays, crops at the top are dropped as items, as if they were harvested.

More Info:

• Tilling a dirt block which has a dirt block on top of it will change it to farmland even though it cannot be used. If a hoe is used on a block horizontally adjacent to such a block, the first block will revert to dirt and the selected block will not be tilled.
  
  
• Ladders and trapdoors cannot be attached to the side of a farmland block, but signs can.
  
  
• Farmland will not be trampled when walking off of a slab next to it.
  
  
• Farmland will not decay if the player 'jumps' onto it, with a block two blocks above the farmland being jumped on.
  
  
• Grass that has water flowing over it cannot be tilled; however, dirt that has water flowing over it can.
  
  
• The flowing water that comes off of a source block hydrates farmland just as source blocks do.
  
  
• Despite farmland looks as tall as a grass path, which is 1 pixel lower then a normal block, it is actually a full block.
  
  
  
  
  
  
• 
  Gallifreyan Snowy Grass Block State

Details will be added soon. In a nutshell, when there's a layer of snow on a Gallifreyan Grass Block, it will retexture itself

• 
  Gallifreyan Grass Changes (copied again from MCW)

Growth:

Grass grows spontaneously only during map generation. Afterward, it can only spread to a nearby dirt block. Grass spreading without player intervention depends heavily on the time of day. In order for a dirt block to accept grass from a nearby grass block, the following requirements must be met:

The dirt block receiving grass must be within a 3×3×5 range of the source block where the source block is in the center of the second topmost layer of that range,

The source block must have a light level of 9 or brighter directly above it,

The dirt block must have a light level of at least 4 above it,

Any block above the dirt block must not reduce light by 2 levels or more.

Light-reducing blocks include any opaque block, as well as lava, water, ice, and partially transparent blocks like stairs and single slabs. Grass blocks can grow under all other transparent blocks like glass, fences, torches, or pistons. Grass jumps directly from one block to a neighbor and is not affected by gaps or other blocks being "in the way". Grass blocks spread at random intervals and have an equal chance of spreading to any suitable dirt blocks that are in range. Because grass can spread as much as 3 levels downward, it tends to spread down slopes much faster than it spreads up them.

Some of the hues that grass blocks can be

The coloration of grass blocks is dependent on the biome they are in. A grass block will always use the hue set to its location, regardless of how it was placed or of its source.

Death:

Grass will die and change to dirt after a random time if covered by any block that reduces the light level above the grass block to 4 or below, including any opaque blocks, or the surrounding area is brought to sufficient darkness. Transparent blocks directly over grass can't kill the grass directly, however the grass will die if the surrounding area provides sufficient darkness.

Tilling a grass block with a hoe will convert it to a farmland block.

I'll reformat this post later today. I'm really tired and need to go lie down for a bit