wiggled around and then lifted out, making a slightly conical airway
from top to bottom. Perforated plastic vent pipes can be left in the
heap. With the help of these airways, no part of the pile is more
than a couple of feet from oxygen

_Moisture. _A dry pile is a cold pile. Microorganisms live in thin
films of water that adhere to organic matter whereas fungi only grow
in humid conditions; if the pile becomes dry, both bacteria and
fungi die off. The upwelling of heated air exiting the pile tends to
rapidly dehydrate the compost heap. It usually is necessary to
periodically add water to a hot working heap. Unfortunately,
remoistening a pile is not always simple. The nature of the
materials tends to cause water to be shed and run off much like a
thatched roof protects a cottage.

Since piles tend to compact and dry out at the same time, when they
are turned they can simultaneously be rehydrated. When I fork over a
heap I take brief breaks and spray water over the new pile, layer by
layer. Two or three such turnings and waterings will result in
finished compost.

The other extreme can also be an obstacle to efficient composting.
Making a pile too wet can encourage soft materials to lose all
mechanical strength, the pile immediately slumps into a chilled,
airless mass. Having large quantities of water pass through a pile
can also leach out vital nutrients that feed organisms of
decomposition and later on, feed the garden itself. I cover my heaps
with old plastic sheeting from November through March to protect
them from Oregon's rainy winter climate.