Humus

Humus is a variant of dark dirt that appears only in forests. Humus is similar to a dark grass block, except that it looks different and that it does not grow to adjacent blocks.

Humus can only be obtained using silk touch tools, or by using commands. When mined with a regular tool or hand, it will drop dark dirt instead.

It's texture represents the rotting dead leaves that fell from trees. Currently humus does not have any special abilities in growing plants.

Generation
Humus is a replacement for dark grass blocks in the forest biome. It generates as an one-block layer on the surface. It does not generate underwater.

Decaying
Humus does not decay into dark dirt by any means, except when it is mined without silk touch. However, humus should decay like dark grass blocks do, though a bug stops the decaying from happening.