There are several methods of harvesting vermicompost. Harvesting may be gradual or by bulk at one time. It is normally done during daytime for ease in separating the earthworms.
The vermicompost is ripe and ready for harvest when the raw materials, except for a few, particularly pieces of woody stem, are fully decomposed. At this stage the vermicomposting ingredients would have undergone both thermophilic and mesophilic processes of decomposition.
of the pile would have dropped down to about one-third to one-half of that of
the original pile; and the pile temperature would be close to ambient
temperature. The organic substrates are no longer distinguishable and the vermicompost
appears somewhat darkish brown, crumbly, and smells earthy, like that of a freshly excavated fertile soil.
However, it is difficult to ascertain ripe or finished compost by visual inspection and other human senses. To be sure, it has to undergo stability or quality test. By the Jar Test, a compost that is finished and safe to plants as soil amendment would not emit a strong offensive odor.
In this paper, the term “vermicompost” is used rather loosely, without regard as to whether it is fully decomposed and stable as defined above. It includes the earthworm castings, also called vermicast.
Common methods (or techniques or procedure) of harvesting vermicompost or vermicast from a heap or pile are briefly described below. Any method may be applied exclusively by preference, subject to some limitations. Otherwise, two or more methods may be practiced on the same pile. Except for the first method, the rest is intended for harvesting in bulk at one time.
1. Gradual, manual harvesting of vermicast – This method is
practiced where a gardener wishes to collect small amounts of vermicast just
a few days after the compost
pile is stocked with composting worms. This becomes a resort when, for example, the gardener finds need of organic
soil amendment as ingredient in preparing a fertile potting mix. In this case
the pile has not been fully decomposed but the top is covered with a layer of vermicast.
earthworm casts on top of the pile are simply gathered by hand or with a trowel
and transferred directly into a container. Otherwise, vermicasts are first
moved to the center of the pile to form a single heap and then scooped into a
container. Earthworms, if any, are picked individually and returned to the
2. Bulk harvesting by pyramidal heap – The vermicompost
is first gathered to form a pyramid- or cone-like heap within the composting enclosure
provided that the heap is exposed to light. Otherwise, the vermicompost is
transferred on to a flat surface elsewhere in open sun over which a plastic sheet or sack or some other substitute is spread.
of harvesting vermicompost takes advantage of the earthworms’ sensitivity to
light (and heat). If the pyramid is exposed to bright light, the earthworms
will tend to move deep into the pyramid.
from the bottom, sides, and top surface of the heap are then collected by hand
or with a trowel. A few minutes are
allowed to pass to provide sufficient time for the earthworms to move deeper
and another cycle (harvesting-resting) is commenced.
there be undecomposed substrates and earthworms, they are collected manually in
For faster rate of harvesting vermicompost, the original heap is better divided into several smaller pyramids. Harvesting is rotated among the pyramids so that after harvesting, one is rested and the next cycle goes to another pyramid.
3. Harvesting by screening – This method of harvesting vermicompost can be applied anytime of the day or even at night. It also has the advantage of ease in separating the vermicompost, undecomposed substrates, and earthworms from each other.
This can be done manually using the same fabricated tool used in screening out rough sand for masonry work. This tool consists of mesh wire nailed on wood.
A small portion of the pile is first transferred into a screener (or sieve or sifter) which is positioned above a container (for example a wheelbarrow) or concrete flooring or flat ground over which a sheet is spread.
is shaken so that fine vermicompost falls toward the ground. Any undecomposed
subtrates which are retained in the screener and the earthworms are separated
4. Harvesting after inducing the migration of eathworms –
This method of harvesting vermicompost is based on earthworms’ ability to
detect sources of food. They also have the habit of abandoning the pile exhausted
of food and moving towards more palatable source.
are many modifications of the technique, but the basic principle is the same:
provide fresh, or otherwise more palatable food to cause the migration of
earthworms from the ripe pile to the new food source.
technique involves constructing a new enclosure adjacent to the one with ripe
compost in such a way that the two enclosures share a common boundary. The new
enclosure is filled with fresh vermicomposting substrates. When it is ready to
be stocked with earthworms, the common boundary, which may consist of hollow
blocks, is then removed. This allows the migration of earthworms towards the
Free of earthworms, the vermicompost should be easy to harvest with the use of a shovel. If there are undecomposed substrates, like wood chips and stem segments which are hard to decompose, they are separated manually. However, the migration of earthworms can take several days to complete.
Note: Earthworms can be manually picked
from the pile anytime. But try this:
Based on their migratory habit as described above, try harvesting earthworms
from harvestable vermicompost pile or from one approaching maturity using balled cattle
manure or some other food or food mixture (try reject cabbage also). First wrap
the earthworm food with a nylon netting with holes sufficient to allow passage
of earthworms. Fasten to a plastic twine or small rope or wire. Then insert the
balled food into the pile leaving some segment of the twine on top. It is expected that the earthworms will bore into this ball of food.To harvest the earthworms,
lift the balled food by the twine. Then crumble the balled food and pick the earthworms.