early curing process give compost some of its disease-
suppressing qualities. On the other hand, beneficial
organisms require sources of food to sustain them. Thus,
if composts are allowed to cure for too long—depleting
all the available food sources—disease suppression
qualities may decrease and eventually be lost.
OTHER cOMPOSTINg TEcHNIQUES
High-temperature piles account for most composting
in the U.S., but other methods are also used. Instead
of making piles, small farmers in developing countries
often dig pits for composting (figure 13.4), especially in
Figure 13.4. An example of a belowground composting pit, often used by
dry and hot climates. The pits can be covered with soil
small farmers in tropical countries.
material to prevent animals from getting into them, and
The curing Stage
they retain moisture in the compost material better.
Following high-temperature composting, the pile should
Vermicomposting involves the use of earth-
be left to cure for about one to three months. Usually,
worms—typically red worms—to perform the decom-
this is done once pile temperatures cool to 105°F and
position process. The method is, in a way, still mostly
high temperatures don’t recur following turning. Curing
bacteria based, but the process occurs in the gut of
is especially needed if the active (hot) process is short or
the worm. The end product is worm casts, coated with
poorly managed. There is a reduced need to turn the pile
mucus consisting of polysaccharides that make them
during curing because the phase of maximum decompo-
into somewhat stable aggregates. The system requires
sition is over and there is significantly less need for rapid
bedding material—like newspaper strips, cardboard,
oxygen entry into the pile’s center when the decomposi-
hay, and similar materials—that mimics the decaying
tion rate is slow. (However, the pile may still need turn-
dried leaves that worms find in their natural habitat.
ing during the curing stage if it is very large or didn’t
The process is fast and efficient—worms can process half
really finish composting—determining when compost is
their weight in organic material in one day. The final
finished is sometimes difficult, but if it reheats, it is not
product has an attractive feel and smell and is appealing
finished—or is soaked by rain.) Curing the pile furthers
to consumers.
aerobic decomposition of resistant chemicals and larger
Vermicomposting is often used to process kitchen
particles. Common beneficial soil organisms populate
scraps and can be done indoors in small bins. Recently,
the pile during curing, the pH becomes closer to neutral,
vermicomposting methods have been developed for
ammonium is converted to nitrate, and soluble salts are
large commercial operations. Two main approaches
leached out if the pile is outside and sufficient precipita-
are used, using windrows or raised beds. With wind-
tion occurs. Be sure to maintain water content at the
rows, new materials are added on one side of the bed,
moisture-holding capacity (around 50% or less during
and the other side is harvested for compost after about
curing) to ensure that active populations of beneficial
sixty days. With the raised-bed or container system—
organisms develop.
preferred for indoor operations in colder climates—the
It is thought that the processes that occur during the
worms are fed at the top of the beds and the castings
146
Building SoilS for Better CropS: SuStainaBle Soil ManageMent