I realized after my post regarding worm castings storage (and the emails
that post generated) that we may not have adequately addressed the issue
of moisture content as it relates to storage. Plastic containers are
often viewed as advantageous for castings storage because they do not
breathe and will help to hold moisture in the material. When castings
have a moisture content no greater than that of potting soil from a
freshly opened bag (approximately 15%-30% moisture) the plastic helps to
maintain that moisture level, preventing rapid drying and, thus, the
potential damage to the biology. This relatively low moisture level
also ensures that oxygen flow/diffusion through the materials is
sufficient to maintain aerobicity. If the castings are too wet,
however, air flow, and more importantly oxygen diffusion through and
into the castings "pellets" can be decreased, a condition further
exacerbated in plastic containers by the fact that plastic does not
allow for fresh air movement into the container as well as do more
porous materials like wood. So, in our discussions of how best to store
castings we need to include the topic of moisture level.
When castings first come out of a worm system they tend to be rather
wet. It is best to dry them before storing by spreading in thin layers
in a protected environment like a barn or garage floor. This should be
done out of direct sunlight as UV light can damage the beneficial biota,
and fans are not recommended as they can cause rapid drying of the
surface material. If there is insufficient room to spread the castings
they can be piled, but the pile should be periodically turned to prevent
over-drying of the surface materials while the center of the pile
remains wet and can potentially become anaerobic. Frequent turning is
not necessarily recommended, however, as another advantage to this
drying phase is that it is also allowing the fungal biomass in the
material to increase (in castings that had sufficient fungal content and
fungal foods to begin with). Frequent turning can inhibit this process.
While we do not want castings to be stored in an overly wet condition,
nor do we want them to dry completely. While 15% moisture will actually
feel very dry (castings will flow very much like dry sand at this
moisture level) there is still a fair amount of water associated with
the stuff. Castings that are completely dry will feel gritty and sharp,
like sand, and become hydrophobic, meaning they will not be re-wetted.
You can leave completely dried out castings in a bucket of water for a
month and they will not adequately recover their ability to hold water.
So dry them down, but don't dry them out!
I hope this provides a more comprehensive explanation for storing
castings and helps to provide a base of information that helps folks
make a better informed decision on castings storage concepts. I
apologize if my previous post caused confusion!
Kelly
Kelly Slocum
Chief Science Officer, Vice President
Bon Terra, Inc.
phone 360.253.5465
fax 360.253.5466
email kelly_at_bonterra.net
Received on Thu Jan 01 2004 - 22:50:55 EST