40d:Mud

Mud can be created by filling a floor space with water, then letting it evaporate. Creating mud is the goal of irrigation.

Mud will spread as your dwarves walk through it and into other areas. It can quickly spread from a farming area throughout your entire fortress, turning floor tiles brown. Floor Grates over a channel or bridges seem to stop the spread.

Mud will completely dry over the winter if it lies undisturbed for the entire time. Barring your dwarves from going outside is the only way to allow all the mud to completely dry. If mud exists within your fort, it will dry during this time and indoor mud can be cleaned by dwarves with this profession enabled.

Example of Stopping Mud Spread

WWWWWWWWWWW
W=====WWWWW
W=====WWWWW
W=====Wó.óW
W=====WW.WW
W=====+#...
W+WWW+WWWWW
W1WWW7WWWWW

Code:
W - unmined [[wall]]
= - farm plot
+ - doors (water inlet/outlet, farmer entance)
# - floor grate
7 - water source
1 - water drain
ó - levers connected to doors
. - clean(!!) ground

Remember that a channel must be built in the tile before the grate is installed. I guess mud can originate from a number of sources besides your own farming, but with enough grates, the fancier parts of the fortress should be safe.

In adventurer mode mud objects which you can pick up from muddy tiles are edible. ^{v0.27.169.33c}