Page 526 - Biosystems Engineering

498 Cha pte r Se v e ntee n

After the vermicompost is harvested, earthworms can be sepa-
rated either manually or by screening through a net 2 mm in size.
However, the latter process of earthworm separation is more conve-
nient and economical than the former. After separation, the cocoons
and the baby earthworms may remain with the vermicompost. After
earthworm separation, the moisture is brought to a 20 to 25 percent
level before bagging. During the dry season, vermicompost gets dried
in the open sun, whereas, during the rainy season, drying in the open
becomes difficult.
The harvested vermicompost is spread on a screen where the
earthworm gets separated and remains above the screen while the
vermicompost moves downward through a series of plates. During
that movement, hot air blows with an air temperature of about 50°C
to bring down the moisture content of the compost to a desired level.
Finally, the dried compost falls on a conveyor belt, which is bagged in
the same unit. The capacity of the machine is 100 kg/h.

Vermiwash
Besides the production of solid vermicompost, another product (i.e.,
liquid manure or vermiwash) is obtained in the composting process.
During watering of compost beds, excess water percolates through
the compost material and is collected in a tank. All the soluble nutri-
ents, enzymes, humic acids, and hormones are washed through the
body of the earthworm and vermicompost, which is a rich fertilizer
material used as a liquid manure. A minimum 100 L of vermiwash
can be harvested per year from each vermibed (see Table 17.2). Vermi-
wash is generally used as a foliar spray to the crops and also in bodies
of water in fish farming to increase production of phytoplankton and
zooplankton.

Parameters Vermicompost Vermiwash*
pH 6.9 6.9
N, % 1.60 0.0046
P, % 0.98 0.0025
K % 1.10 0.063
O, C, % 14.1 —
Cu, ppm 38.0 0.117
Zn, ppm 180 0.132
Ca, ppm 2760 786
Mg, ppm 4100 328
Fe, ppm 11200 0.151
Mn, ppm 1290 213

∗From Basak and Ghosh. 22
TABLE 17.2 Composition of Vermicompost and Vermiwash