Agriculture Reference
In-Depth Information
TABLE 18.1
Maximum Reproduction Rate of Earthworms in Animal and
Vegetable Wastes: Cocoon Production
No. of
Cocoons
%
Hatch
No. of
Hatchlings
Net Reproductive
Rates per Week
Species
Eisenia fetida
3.8
83.2
3.3
10.4
Eudrilus eugeniae
3.6
81.0
2.3
6.7
Perionyx excavatus
19.5
90.7
1.1
19.4
Dendrobaena veneta
1.6
81.2
1.1
1.4
TABLE 18.2
Productivity of Earthworms in Animal and Vegetable Waste:
Length of Life Cycle
Time for Cocoons
to Hatch (days)
Time to Sexual
Maturity (days)
Time Egg to
Maturity (days)
Species
Eisenia fetida
32Ï73
53Ï76
85Ï149
Eudrilus eugeniae
12Ï27
32Ï95
43Ï122
Perionyx excavatus
16Ï21
28Ï56
44Ï71
Dendrobaena veneta
40Ï126
57Ï86
97Ï14
produced 24 cocoons (13 young earthworms), and
produced 10 cocoons (9.5 young
earthworms) per parent earthworm. These researchers also studied the rates of growth of different
multispecific combinations of these species in polyculture. Although the total earthworm biomass
tended to be greater in polyculture, the results were not clear cut because different species eventually
became dominant in different wastes and climatic conditions.
Edwards (1988) studied the life cycles and optimal conditions for growth and survival of
P. hawayana
E.
fetida, D. veneta, E. eugeniae,
in animal and vegetable wastes (Table 18.1 and
Table 18.2). Each of the four earthworm species differed considerably in terms of response to and
tolerance of different temperatures. The optimum temperature for growth of
and
P. e xcavatus
E. fetida
was 25
A
C,
had a lower temperature optimum and was
less tolerant of extreme temperatures. The optimum temperatures for
with a temperature tolerance from 0 to 35
A
C.
D. veneta
E. eugeniae
and
P. e xcavatus
were also about 25
A
C, but they died at temperatures below 9
A
C and above 30
A
C. The optimum
temperatures for cocoon production for all species were much lower than for growth (
Figure 18.2
).
These four species also differed in their optimum moisture requirements from those of
E. fetida,
but the differences were not great (
Figure 18.3
)
. The range over which the earthworms grew
optimally was quite narrow, with optimal growth at 80 to 55% moisture content, with considerable
decreases in growth at moisture contents of 70 and 90%. However,
D. veneta
was able to withstand
a much wider range of moisture contents than the other species, such as
P. e xcavatus.
All four species of earthworms were very sensitive to ammonia and did not survive long in
organic wastes containing much ammonia (e.g., fresh poultry litter). They also died in wastes
containing large quantities of inorganic salts. Laboratory experiments showed that both ammonia
and inorganic salts have very sharp cutoff points between toxic and nontoxic levels (i.e., <0.5 mg
per ram ammonia and <0.5% salts). However, organic wastes that have too much ammonia became
acceptable after the ammonia was removed by a period of composting or when both excessive
