5. discussion - shodhgangashodhganga.inflibnet.ac.in/bitstream/10603/9675/12/12...laboratory...
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5. DISCUSSION
5.1 Cocoon production of adult earthworms
The rate of cocoon production observed in the adult L.mauritii cultured in 100 PSR
dose of organic mixture (Table 11) and P.excavatus in 100 PSR dose of paddy waste
materials (Table 8) was the highest (0.216 and 0.097 cocoon/ worm/day respectively) among
the four organic materials (water hyacinth, paddy waste, cow dung and organic mixture)
studied for the present study. Similarly the rate of cocoon production observed in the same
earthworms respectively grown in10 PSR dose of paddy waste (Table 7) and organic
mixture (Table 12) was the least (0.025 and 0.013 cocoon/worm/day respectively) among the
same four organic materials studied. Like the current study, different rates of cocoon
production were also reported in L.mauritii cultured under different organic substrates. For
example 0.4 cocoon/worm/day in 100% press mud medium (Ramalingam, 1997), 0.150,
0.006 and 0.080 cocoon/worm/day respectively in the substrate medium containing 50% cow
dung, press mud and organic mixture (cow dung + press mud + paddy chaff powder + paddy
chaff ash) at 32 ± 2°C (Bakthavathsalam and Ramakrishnan, 2004), 0.06 and 0.04
cocoon/worm/day respectively in the substrate medium containing 20 % paddy chaff powder
and weed plants materials at 30 ± 2°C (Bakthavathsalam and Geetha, 2004a), 0.025 and
0.030 cocoon/worm/day respectively under the substrate medium containing 20 % press mud
and cow dung at 30 ± 2°C (Bakthavathsalam, 2007a), 0.025 to 0.05 cocoon/worm/day under
50% cow dung over a period of 12 months at laboratory condition (Bakthavathsalam and
Birmanandhi, 2007) and 0.066 cocoon/worm/day under 25% vegetable market waste at 30 ±
2°C (Bakthavathsalam and Uthayakumar, 2007). The rate of cocoon production observed in
L.mauritii is usually high as in other species namely D.willsi and O.surensis due to their
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surface dwelling nature and their activity confined only to 20 cm deep during winter and
30cm during summer seasons (Dash and Senapati, 1980). Similarly Evans and Guild (1948)
and Bhattacharjee and Chaudhuri (2002) have also noted a production rate of 42 – 106
cocoons per year in the surface dwelling earthworms, L.rubellus and Lumbricus castaneus
and 43 cocoons/worm/year in the geophagous species, L.mauritii respectively. Under
laboratory conditions, Evans and Guild (1947) and Kaviraj and Sharma (2003) have also
reported a production rate of 3.7 cocoons/worm/month and 8.6 cocoons/week respectively in
L.terrestris and L.mauritii. Similarly Meinhardt (1974) has also reported a production rate of
4 – 6 cocoons/worm/month all through the year in the endemic earthworm species,
L.terrestris. Monroy et al. (2007) have also reported a similar rate, 0.82 ± 0.14
cocoon/worm/week in O.complanatus cultured in the substrate medium containing cow
manure alone.
Different rates of cocoon production were also reported in the earthworm species,
P.excavatus exposed to different substrates. For example 0.15 cocoon/worm/day as
production rate in the substrate medium containing cattle solids maintained at 25°C (Kale
et al.,1982), 1.4 cocoon/worm/day in urine free cattle droppings at 25°C (Reinecke and
Hallatt, 1989), 0.44 ± 0.09 cocoon/worm/day in cattle manure at 25°C and 80 ± 0.10%
moisture (Hallatt et al .,1992), 0.12 cocoon/worm/day in cattle solids at 25 – 37°C (Reinecke
et al., 1992), 0.82 and 0.29 cocoon/worm/day respectively in cattle solids at 25 and 30°C
(Edwards et al.,1998), 0.15 cocoon/worm/day in farmyard manure and 0.23
cocoon/worm/day in mixed crop residue added with cow dung (1:1ratio) at 29.4°C
(Suthar, 2007b), 203.4 ± 0.02 cocoons/60 days in press mud at 31 ± 2°C and 65 – 67%
relative humidity (Parthasarathi, 2007), 1.1 ± 0.05 cocoon/worm/day in cow manure and oak
litter at 20 – 25°C (Namita and Madhuri, 2008) and 0.13 ± 0.005 cocoon/worm/day in
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domestic waste (house hold waste) under laboratory condition (Suthar and Singh, 2008).
Similar type of effects were also resported in other earthworm species with a production rate
as 0.7 ± 0.01 cocoon/worm/day in D.nepalensis, and 0.04 ± 0.002 cocoon/worm/day in
M.houlleti after exposure to cow manure and oak litter at 20 – 25°C (Namita and
Madhuri, 2008), 0.315 and 0.082 cocoon/worm/day in E.eugeniae respectively after exposure
to 100 and 10 PSR doses of green gram waste at 31 – 36°C (Jayaseelan and
Bakthavathsalam, 2009a), 0.069 and 0.017 cocoon/worm/day in E.eugeniae respectively after
exposure to 75 and 10 PSR doses of paddy straw waste at 31 – 36°C (Subramaniyan and
Bakthavathsalam, 2009), 0.074 cocoon/worm/day in E.eugeniae after exposure to coir waste,
E.crassipes, cow dung and poultry excreta mixture (Bakthavathsalam et al.,2010c), and
0.025 cocoon/worm/day in E.eugeniae after exposure to coir waste, water lily, goat
droppings and poultry excreta mixture (Bakthavathsalam et al.,2010d) have also been
reported.
5.1.1 Hatchling production
The hatching rate of cocoons collected from L.mauritii under 50 PSR dose of cow
dung (1.08 hatchling / cocoon) (Table 9) and P.excavatus under 100 PSR dose of cow dung
(1.11 hatchling / cocoon) (Table 10) was relatively very high when compared to other doses
or organic materials studied for this study. The current hatching rates coincide with the
reported results of Dash and Senapati (1980) in L.mauritii and Kaushal et al. (1995) in
D.nepalensis where they observed more than one juvenile from a single cocoon. However
most of the hatching rates observed in the current study were found to be very less when
compared to other earthworm species such as P.hawayana with 1.2 in aerobically maintained
sludge (Loehr et al., 1985), E.fetida with 2.7 in cattle manure (Venter and Reinecke, 1988;
and Ramalingam, 1997), E.fetida and E.eugeniae with 3.3 and 2.3 in animal, vegetable and
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industrial organic wastes (Edwards,1988), E.eugeniae and L.mauritii with 2.63 and 3.15 in
press mud (Ranganathan and Parthasarathi ,1999), L.mauritii with 1.67 ± 0.11 in pasture
soil (Bhattacharjee and Chaudhuri, 2002), L.mauritii with 1.4 in cow dung (Bakthavathsalam
and Ramakrishnan, 2004) and 1.83 in press mud (Bakthavathsalam, 2007a), E.eugeniae with
1.4 in coir waste, water lily, goat droppings and poultry excreta mixture (Bakthavathsalam
et al., 2010d), 2.77 in cow dung (Viljoen and Reinecke, 1989) and 2.2 in cattle manure
(Viljoen and Reinecke, 1994), Dendrobaena rubida with 1.67 in cow manure (Elvira
et al., 1996b), E.eugeniae with 1.4 and E.fetida with 1.3 in rubber leaf litters (Chaudhuri
et al., 2003), P.excavatus with 2.45 and 1.37 respectively in cow dung and kitchen wastes
(Chaudhuri and Bhattacharjee, 2002), and E.eugeniae, P.excavatus, E.fetida and L.mauritii
respectively with 2.3, 3.2, 1.6 and 1.8 in sugar cane trash, bagasse and press mud mixture
(Manivannan et al., 2004).
5.1.2 Hatching success
The cocoons collected from P.excavatus exposed to different doses (barring few
cases) of water hyacinth (Table 6), paddy waste (Table 8), cow dung (Table 10) and organic
mixture (Table 12) showed 100% hatching success. Similar hatching success was also
noticed in the studies made by Bakthavathsalam and Ramakrishnan (2004) in L.mauritii
exposed to cow dung, press mud and organic mixture, Bakthavathsalam (2007a) in L.mauritii
exposed to press mud and cow dung, and Bakthavathsalam et al. (2010d) in E.eugeniae
exposed to a organic mixture containing coir waste, water lily, goat droppings and poultry
excreta.
On the contrary relatively lower rates (<100%) of hatching success were noticed in the
other earthworm, L.mauritii (over P.excavatus) exposed separately to different doses (most
of the cases) of all organic materials (Tables 5, 7, 9, 11). Similarly lower rates of hatching
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success were also reported from the studies made by Loehr et al. (1985) in E.eugeniae
exposed to aerobically maintained sludge (73%), Edwards (1988) in E.fetida exposed to
animal and vegetable wastes (83%). Sheppard (1988) in E.fetida (82.2%) and E.andrei
(73.5%) exposed to cow manure, Haimi (1990) in E.fetida (77.5%) and E.andrei (85%)
exposed to various composts, Reinecke and Viljoen (1991) in E.fetida (89.2%), E.andrei
(90.5%) exposed to cow gut content, Kaushal et al.(1995) in D.nepalensis exposed to soil
and pine littre (92%), Elvira et al.(1996a) in E.fetida (88.3%) and E.andrei (88.1%) exposed
to cow manure, Edwards et al.(1998) in P.excavatus exposed to cattle solids (91%),
Dominguez et al.(2001) in E.eugeniae exposed to cattle solids (81%), Bhattacharjee and
Chaudhuri (2002) in L.mauritii (60%), P.corethrurus (85%) P.elongata (40%), D.modiglianii
(78%) and P.excavatus (52.5%) exposed to posture soil, Bakthavathsalam and
Geetha (2004a) in L.mauritii exposed to paddy chaff powder (96%) and weed plants material
(80%), Dominguez et al.(2005) in E.fetida (61.2%) and E.andrei (56.8%) exposed to cow
manure, Monroy et al.(2007) in O.complanatus exposed to cow manure (55%) and
Sudhar (2007a) in P.excavatus exposed to an organic mixture (1:1:2) containing jowar straw
bajara straw, boyar straw and sheep manure (56.0 ± 2.34%), farmyard manure (54.84 ± 0.90)
and kitchen waste with Magifera indica leaf litter (74.34 ± 2.38%).
5.1.3 Incubation time
The incubation time observed in the cocoons obtained from L.mauritii exposed to
water hyacinth (Table 5) and organic mixture (Table 11) showed a constant value 20 – 23
days irrespective of doses exposed. And in contrast, cocoons obtained from L.mauritii under
paddy waste (Table 7) and cow dung (Table 9) and from P.excavatus exposed to all four
organic materials (Table 6, 8, 10 and 12) showed a dose dependant effect with lesser
incubation time in lower doses (10 – 30 PSR) and higher time in higher doses (40 – 100
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PSR). Though the incubation time observed in P.excavatus cocoons exposed to animal
vegetable and industrial waste (16 – 21 days) by Edwards (1988), cattle solids (19 days) by
Edwards et al. (1998), cattle manure (19.4 ± 0.72 days) by Hallatt et al. (1992), cattle manure
(17.8 days in 25°C and 15.3 days in 25 – 37
°C) by Reinecke et al. (1992), posture soil
(12.80 ± 0.31 days) by Bhattacharjee and Chaudhuri (2002) and cow manure and oak litter
(18.7 ± 1.8 days) by Namitha and Madhuri (2008) showed similar values as in the current
study with higher doses of organic matter, the exact reason for varied incubation time was
not known at present but it needs further investigation.
Similar type of embryonic development was also reported from other earthworm
species using different organic matters. For example 14.93 ± 0.51 days for L.mauritii and
14.16 ± 0.48 days for D.modiglianii exposed to posture soil by Bhattacharjee and
Chaudhuri (2002), 12 – 17 days for E.eugeniae exposed to paddy straw waste by
Subramaniyan and Bakthavathsalam (2009), 14 ± 2, 14 – 17, 12 – 16 and 14 – 15 days for
the same earthworm exposed to cattle solids, green gram waste, coir waste + E.crassipes +
cow dung + poultry excreta mixture and coir waste + water lily + goat droppings + poultry
excreta mixture respectively by Dominguez et al. (2001), Jayaseelan and
Bakthavathsalam (2009a), Bakthavathsalam et al. (2010c) and Bakthavathsalam
et al. (2010d).
It is very common that the cocoon incubation time of any earthworm species vary from
one earthworm to another, from one soil temperature to another, from one moisture level to
another and from one organic matter to another. But it is unusual that the cocoons collected
from lower doses of organic matter in the present study showed lesser incubation time and
vice versa is the case in higher doses. Such type of information was not available in the case
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of any earthworm cocoons cultured under any specific organic matter and hence it needs
further investigation to arrive at a specific conclusion.
5.1.4 Change of body weight during cocoon laying
The adult earthworms (L.mauritii and P.excavatus) exposed to lower doses (up to
40 PSR) of all organic materials (water hyacinth, paddy waste, cow dung and organic
mixture) in general showed marginal changes (either meagre loss or gain values) in their
body weight during the course of this cocoon production study. Control earthworms (0 PSR),
on the other hand, showed over all reduction values in their body weight. The reduction
observed in the body weight of control and experimental earthworms exposed to lower doses
may be due to non availability of sufficient nitrogen and other essential nutrients required for
their cocoon production as reported by Jena et al. (2002). However the earthworms exposed
to higher doses showed over all gain values in their body weight during the course of this
study. The weight gain values observed in the earthworms exposed to higher doses of organic
wastes follows the findings of Bisht et al.(2006) in O.trytaeum exposed to litter diets of
maize, grass and wheat (with 54.9, 45.3 and 45.9% weight gain), Parthasarathi (2007) in
P.excavatus exposed to press mud under 65 – 67 % moisture level (with 92% weight gain),
Bakthavathsalam and Geetha (2004a) and Bakthavathsalam (2007a) in L.mauritii
respectively exposed to paddy chaff powder and weed plants materials (with 35.5 and
128.5% weight gain respectively), and press mud and cow dung (with 6.75 and 7.81% weight
gain respectively), Jayaseelan and Bakthavathsalam (2009a) in E.eugeniae exposed to green
gram waste (+115%), Subramaniyan and Bakthavathsalam (2009) in E.eugeniae exposed to
paddy straw waste (+12.3%), Bakthavathsalam et al.(2010c) in E.eugeniae exposed to coir
waste + E.crassipes + cow dung + poultry excreta mixture (+24.5%) and Bakthavathsalam
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et al.(2010d) in E.eugeniae exposed to coir waste+ water lily+ goat droppings + poultry
excreta mixture (+9.19%).
In all the above studies, either cattle dung or plant – derived wastes were used as
substrate for earthworm culture practice however the observed difference (rate of cocoon
production, hatching ability and gain in biomass value) could be due to either the nature and
quality of the feeding materials or varied environmental conditions or variation in the
chemistry of substrate or species – specific feeding behaviour of earthworm or the
combination of different factors.
5.2 Growth study of F1 hatchlings
The mean length of F1 hatchlings of L.mauritii and P.excavatus respectively measured
in 100 PSR dose of water hyacinth (92 ± 5mm) (Table 13) and organic mixture (79 ± 3mm)
(Table 20) was the highest among the four organic materials (water hyacinth, paddy waste,
cow dung and organic mixture) studied. Similar growth reports were also available from the
culture studies made in L.mauritii exposed to cow dung (8.94 ± 0.73cm), press mud (11.75 ±
1.50cm) and organic mixture (9.23 ± 0.99cm) by Bakthavathsalam and Ramakrishnan
(2004), paddy chaff powder (10.0 ± 1.0cm) and weed plants materials (10.3 ± 1.0cm) by
Bakthavathsalam and Geetha (2004b), and cow dung (7.14 ± 0.54cm) and press mud (6.40 ±
0.19 cm) by Bakthavathsalam (2007a).
Invariably the F1 hatchlings obtained from the cocoons of adult L.mauritii exposed to
100 PSR dose of water hyacinth, paddy waste, cow dung and organic mixture for 30 days
showed a gradual increase in their body weight and attained sexual maturity once they
reached their mean body weight to 920mg/worm in cow dung (Table 17), 950mg/worm in
water hyacinth (Table 13) and organic mixture (Table 19), and 960mg/worm in paddy waste
(Table 15) at the age in between the days 60 and 67. But the same F1 hatchlings obtained
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from the lowest dose (10 PSR) attained sexual maturity somewhat later (between 70 and 80
days) than the hatchlings cultured in the highest dose (100 PSR) after reached their mean
body weight to 733mg/worm in water hyacinth (Table 13), 750mg/worm in organic mixture
(Table 19), 791mg/worm in cow dung (Table 17) and 883mg/worm in paddy waste
(Table 15). On the contrary, the F1 hatchlings of adult P.excavatus obtained from the highest
dose(100 PSR) of all organic materials attained sexual maturity within a short span of time
(after 30 – 35 days of growth) once they reached their body weight to 625mg/worm in paddy
waste (Table 16), 650mg/worm in water hyacinth (Table 14) and cow dung (Table 18), and
658mg/worm in organic mixture (Table 20). But the same F1 P.excavatus hatchlings obtained
from the lowest dose (10 PSR) attained sexual maturity only after 50 – 58 days of growth
after they reached their body weight to 479mg/worm in paddy waste (Table 16),
533mg/worm in water hyacinth (Table 14), 576mg/worm in cow dung (Table 18) and
600mg/worm in organic mixture (Table 20). Though such dose dependent effect was not
noticed elsewhere in the earthworms (L.mauritii and P.excavatus) using any type of organic
materials, but the growth study made in E.eugeniae hatchlings under green gram waste and
paddy straw waste respectively by Jayaseelan and Bakthavathsalam (2009a) and
Subramaniyan and Bakthavathsalam (2009) kept in laboratory condition was clearly showed
a dose dependent effect with a longer period in lower doses and a shorter period in higher
doses for their sexual maturity. The belated reproductive maturity observed in the current
study (under lower doses of organic materials) may be due to scarcity of certain
nutrients/elements necessary for their growth and reproductive activities.
As in other culture study, the present study with L.mauritii hatchlings under different
doses of organic materials also followed the same trend with regards to their time of sexual
maturity (barring certain lower doses). But the hatchlings of P.excavatus, on the other hand,
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showed a wide variation in their sexual maturity time while they were in different doses of
organic materials. The first indication of clitellum development in P.excavatus is usually
appeared in between the days 21 and 22 and released their cocoons in between the days 24
and 28 (Reinecke et al., 1992). But in all cases irrespective of doses or organic materials
exposed, the time required for the hatchlings to reach sexual maturity was so long but
differed very much. According to Kale et al. (1982) intra specific interaction controls the
growth of individual worms so that worms of same age may require different lengths of time
to reach their sexual maturity. The present results seem to indicate the existence of intra
specific variation among the individual worms of same species. Compared to earlier reports
(both in P.excavatus and in other earthworm species), the development of clitellum seems to
be very late in all the hatchlings of P.excavatus cultured separately under different doses of
water hyacinth, paddy waste, cow dung and organic mixture. Reinecke and Hallatt (1989)
found the first indications of clitellum development in P.excavatus (cultured in
cattle manure) appears in between the days 14 and 28. Similarly Viljoen and Reinecke (1989)
have also found early indications of clitellum development (between days 25 and 30) in
E.eugeniae. According to Neuhauser et al.(1979) food availability and population density
determine the time of sexual maturation and this could explain the difference between the
present findings and those of Kale et al. (1982), Reinecke and Hallatt (1989) and Viljoen and
Reinecke (1989).
The overall growth rate value observed in F1 L.mauritii (Table 15) and P.excavatus
(Table 20) hatchlings respectively exposed to 100 PSR dose of paddy waste and organic
mixture was the highest (15.70 and 21.73 mg/day/worm respectively) among the 7 PSR
doses and four organic materials (water hyacinth, paddy waste, cow dung and organic
mixture) used in the present study and also the growth study made by Edwards (1988) and
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Hartenstein and Hartenstein (1981) in E.fetida hatchlings respectively exposed to a substrate
containing animal and vegetable wastes (8.9 mg/day) and wet activated sludge
(14mg/worm/day), Cluzeau et al.(1992) in E.andrei exposed to house manure and peat
through batch culture (4.5mg/worm/day), Reinecke et al. (1992) in E.fetida exposed to cattle
manure (7mg/worm/day), Kaushal et al. (1995) in D.nepalensis exposed to a substrate
containing soil and pine litter (10.8mg/day), Elvira et al. (1996b) in L.rubellus exposed to
cow manure (8.0mg/worm/day), Fayolle et al. (1997) in D.veneta exposed to horse manure
(14.1mg/worm/day) and sludge (21.3mg/worm/day), Frederickson (1997) in E.andrei
exposed to an organic mixture containing grasses, garden, municipal prunings and river
weeds (7.2mg /worm/day), Kaushal et al. (1999) in M.houlleti exposed to different food
substrates (2.9 to 4.1mg/worm/day), Bakthavathsalam and Geetha (2004b) in L.mauritii
exposed to paddy chaff powder (8.025mg/worm/day) and weed plants material
(8.937mg/worm/day), Christy and Ramalingam (2005a) in P.excavatus exposed to sago solid
waste with press mud (2:3 ratio) (4.45 mg/worm/day), Garg et al.(2005b) in E.fetida
exposed to biogas plant slurry (12.99mg/worm/day), Bakthavathsalam (2007a) in L.mauritii
exposed to press mud and cow dung (9.285 and 10.24 mg/day), Bisht et al. (2007) in
M.posthuma exposed to cow dung through single and batch culture (8.4 and 7.7
mg/worm/day respectively) and poultry droppings through single and batch culture (7.1 and
4.9mg/worm/day respectively), Chandran and Ramalingam (2007a) and (2007b) in
P.excavatus respectively exposed to paper mill sludge with press mud (1:3 ratio) (2.36
mg/worm/day) and paper mill sludge with cow dung (1:3 ratio) (2.41mg/worm/day),
Purushothaman (2011) in E.fetida exposed to 100 PSR dose of black gram plant waste
(7.25mg/worm/day),100 PSR dose of bagasse (8.54mg/worm/day), 50 PSR dose of cow dung
(8.38mg/worm/day) and 100 PSR dose of organic mixture (8.54 mg/worm/day) and
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Uthayakumar (2011) in E.fetida and L.mauritii respectively exposed to 100 and 50 PSR
doses of sheep droppings (8.20 and 12.87mg/worm/day), 100 and 40 PSR doses of press mud
(8.42 and 12.34 mg/worm/day) 100 and 40 PSR doses of Pongamia leaves (8.63 and 12.79
mg/worm/day) and 100 and 40 PSR doses of organic mixture (8.58 and 12.54mg/worm/day).
However the present growth rate was relatively low when compared to the results reported by
Dominguez et al. (2001) in E.eugeniae exposed to cattle solids (40.0mg/day), Raja and
Ramalingam (2007a) in E.eugeniae exposed to cashew leaves with cow dung (1:3 ratio)along
with lignolytic and cellulolytic fungi (23.14mg/worm/day), Jayaseelan and
Bakthavathsalam (2009a) in E.eugeniae exposed to green gram waste (45.88mg/worm/day),
Subramaniyan and Bakthavathsalam (2009) in E.eugeniae exposed to paddy straw waste
(36.84 mg/worm/day), and Purushothaman (2011) in E.eugeniae exposed to 100 PSR dose of
black gram plant wastes (40.2 mg/worm/day), 100 PSR dose of bagasse
(38.02mg/worm/day), 75 PSR dose of cow dung (34.7 mg/worm/day) and 100 PSR dose of
organic mixture (34.7 mg/worm/day).
5.3 Cocoon production of F1 earthworms
As in adult earthworms, the rate of cocoon production observed in F1 L.mauritii
exposed to 100 PSR dose of organic mixture (0.102cocoon/worm/day) (Table 24) and
P.excavatus exposed to 100 PSR dose of paddy waste (0.097cocoon/worm/day) (Table 22)
was relatively high when compared to other organic matters (water hyacinth and cow dung)
or doses (10 –75 PSR) studied (Tables 21– 24). Similarly a dose dependent effect with lesser
cocoon production rate in lower doses and higher rate in higher doses was noticed as in their
adult parents. However the rate of cocoon production observed in F1 L.mauritii kept under
higher doses of water hyacinth and organic mixture and in F1 P.excavatus exposed to higher
doses of water hyacinth, cow dung and organic mixture was relatively less when compared to
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the rate of cocoon production observed in their adult parents as well as in F1 L.mauritii
exposed to paddy chaff powder and weed plants material (0.13 and 0.15 cocoon/worm/day)
by Bakthavathsalam and Geetha (2004b) and high when compared to the production rate
(0.009 and 0.014 cocoon/worm/day) observed by Bakthavathsalam (2007a) in the same
species (F1 offsprings) exposed to press mud and cow dung.
The F1 mature earthworms (of both species) kept in different doses of organic materials
showed invariably a marginal increase in their body weight during the course of their cocoon
laying. However the weight gain values observed in F1 P.excavatus kept in different doses of
organic materials were relatively high when compared to the weight gain values observed in
F1 L.mauritii. Though all F1 earthworms produced cocoons irrespective of doses or organic
materials exposed, the total cocoons produced by L.mauritii in all the doses were relatively
high when compared to the total cocoons produced by P.excavatus.
Of the four organic materials studied with two F1 earthworms (L.mauritii and
P.excavatus) to know their suitability and usage and their role in biomass production and
reproduction, all the 4 organic materials are considered as good raw materials (since no
adverse effect was noticed elsewhere) for the preparation of culture medium to raise these
earthworms for biomass production in order to meet the protein requirements of food
industry pertaining to fish, poultry and pigs though showed wide variations in their growth
rate and reproduction of the said earthworms.
The per cent weight gain values observed during cocoon production in mature F1
L.mauritii exposed to 40 PSR and P.excavatus exposed to 10 PSR paddy waste (16.7 and
33.9% respectively) (Table 22) were the highest among the 4 organic materials and 7 PSR
doses used in the present study (Tables 21 – 24) but lesser than the results observed in mature
F1 E.eugeniae and E.fetida respectively exposed to 100 PSR dose of black gram plant wastes
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(34.0 and 27.3 %), 100 PSR dose of bagasse (31.9 and 25.9%), 75 PSR dose of cow dung
(36.4 and 22.6%) and 100 PSR dose of organic mixture (27.3 and 26.6%) by
Purushothaman (2011) and in mature F1 E.fetida and L.mauritii exposed to 75 and 50 PSR
doses of sheep droppings (30.0 and 40.8%), 50 and 40 PSR doses of press mud (25.6 and
40.0%), 50 and 40 PSR doses of Pongamia leaves (33.9 and 40.9%) and 75 and 40 PSR
doses of organic mixture (30.4 and 41.1%) by Uthayakumar (2011).
The higher growth rate values during pre reproductive period (before clitellum
development) and lesser during reproductive period (at the time of cocoon production)
observed in F1 earthworms confirmed the earlier reports (Ramalingam,1997) that energy rich
nutrients obtained from the organic materials may be completely utilized by the earthworms
only for their growth purpose during pre reproductive period and part of them for their
growth and survival and most of them for their cocoon production during reproductive period
(at the time of cocoon laying).
5.4 Physico – chemical analysis of vermicomposts
5.4.1 pH
The pH values measured in the partly decomposed water hyacinth, paddy waste, cow
dung and organic mixture samples showed only a basic nature (Tables 25 – 29). But the same
samples obtained after vermicomposting practice with L.mauritii and P.excavatus showed a
reduction in their mean pH values. Such type of pH alterations were also reported from the
studies made by Elvira et al. (1998) in the vermicomposts of E.andrei exposed cattle manure,
paper mill sludge with cattle manure, dairy sludge with cattle manure, and paper mill sludge
with dairy sludge and cattle manure, Benitez et al. (1999) in the vermicompost of E.fetida
exposed sewage sludge, Masciandaro et al. (2000) in the vermicompost of E.fetida exposed
municipal sewage sludge, Ramalingam and Thilagar (2000) in the vermicompost of
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P.excavatus exposed sugar cane trash with cow dung, Bakthavathsalam and Geetha (2004c)
in the vermicomposts of L.mauritii exposed paddy chaff powder and weed plants materials,
Christy and Ramalingam (2005b) in the vermicomposts of 1: 4, 2 : 3 and 3 : 2 ratios of
E.eugeniae exposed press mud and sago solid waste mixtures, Garg et al. (2005 b) in the
vermicompost of E.fetida exposed cow dung mixed with biogas plants slurry and solid
textile mill sludge, Ramalingam and Christy (2006) in the vermicompost of P.excavatus
exposed sago solid waste mixed with press mud, Suthar and Singh (2008) in the
vermicompost of P.excavatus and P.sansibaricus exposed domestic waste, Venkatesh and
Eevera (2008) in the vermicompost of E.eugeniae exposed fly ash mixed with cow dung,
Jayaseelan and Bakthavathsalam (2009b) in the vermicasts obtained from E.eugeniae after
exposure to green gram waste, Subramaniyan and Bakthavathsalam (2009) in the vermicasts
of E.eugeniae after exposure to paddy straw waste, Bakthavathsalam et al. (2010 c) in the
vermicasts of E.eugeniae after exposure to coir waste mixed with E.crassipes, cow dung and
poultry excreta, Bakthavathsalam et al. (2010 d) in the vermicasts of E.eugeniae after
exposure to coir waste mixed with water lily, goat droppings and poultry excreta, and
Umamaheswari and Bakthavathsalam (2010) in the vermicasts of E.eugeniae after exposure
to P.longifolia leaves.
The availability of several plant nutrients and other elements present in any soil
depends upon the pH value of the organic manure. The pH value at near neutral level should
be considered important in retaining nitrogen, since it is lost as volatile ammonia at high pH
(Hartenstein and Hartenstein, 1981; Haimi and Huhta, 1987) and the pH range 6 – 7 seems to
promote the availability of plant nutrients (Brady, 1988). In the present analysis, though the
pH value was not reduced so greatly during vermicomposting practice, but it is maintained in
the safe range between 6 and 7 as suggested by Brady (1988). Hence it could be concluded
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that the observed pH values in the vermicomposts obtained from the said organic materials
after digested by earthworms are the optimum level for the plants to get available free
nutrients for their better growth and yield as revealed in the pot culture experiments carried
out with chilli plant using these organic vermicomposts (Tables 30 – 33).
The reduced pH values observed in the present study may be either due to
accumulation of organic acids obtained from the microbial metabolism or due to production
of CO2, fulvic acid and humic acid during the process of bio conversion of different
substrates under decomposition (Haimi and Huhta, 1986 ; Albanell et al., 1998 ; Chan and
Griffiths, 1988 ; Atiyeh et al., 2000b) or due to mineralization of nitrogen and phosphorus
into nitrites / nitrates and orthophosphates, bio conversion of organic materials into
intermediate species of organic acids (Ndegwa and Thompson, 2001).
5.4.2 EC
The levels of EC measured in the organic materials are generally showed lesser values
once they exposed to L.mauritii and P.excavatus which indicate that the soluble salts level
was greatly reduced during vermicomposting as observed by Elvira et al. (1998) in E.andrei
exposed cattle manure with paper mill sludge and dairy sludge, Masciandaro et al. (2000) in
E.fetida exposed sludges of municipal sewage plant waste, Ramalingam and Thilagar (2000)
in P.excavatus exposed sugar cane trash with cow dung , Ramalingam (2001) in P.excavatus
exposed sugar cane trash with press mud, Ramalingam and Christy (2006) in P.excavatus
exposed sago solid waste with press mud, Venkatesh and Eevera (2008) in E.eugeniae
exposed fly ash with cow dung, Jayaseelan and Bakthavathsalam (2009b) in E.eugeniae
exposed green gram waste, Subramaniyan and Bakthavathsalam (2009) in E.eugeniae
exposed paddy straw waste, Uthayakumar and Bakthavathsalam (2009) in L.mauritii exposed
vegetable market waste, Bakthavathsalam et al. (2010c) in E.eugeniae exposed organic
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mixture prepared from coir waste, E.crassipes, cow dung and poultry excreta and
Umamaheswari and Bakthavathsalam (2010) in E.eugeniae exposed P.longifolia leaves. The
volatilization of ammonia and the precipitation of mineral salts are the possible reason for the
decrease in EC during vermicomposting as suggested by Wong et al. (1995).
5.4.3 Macro and micronutrients
Of the 6 macronutrients (OC, TN, TP, TK, TNa and TCa) and 4 micronutrients (Fe,
Mn, Zn and Cu) analysed in the samples of partly decomposed and vermicomposts of
L.mauritii exposed and P.excavatus exposed water hyacinth, paddy waste, cow dung and
organic mixture, the levels of OC in macronutrients and Fe in micronutrients were relatively
high when compared to other macro and micronutrients present in the organic materials (all
partly decomposed and earthworm exposed organic materials) (Tables 26 – 29). Similarly of
the two earthworm exposed organic samples analysed, the L.mauritii exposed organic
samples showed relatively more nutrients than the P.excavatus exposed organic samples.
During vermicomposting, L.mauritii significantly improved the levels of TN, TP, TK, Mn,
Zn and Cu in water hyacinth, OC, TN, TP, TK, TCa, Mn, Zn and Cu in paddy waste, OC,
TN, TP, TK, TCa, Mn and Cu in cow dung and OC, TN, TP, TCa, Fe, Mn, Zn and Cu in
organic mixture. Similarly the levels of TN, TP, TCa, Fe, Zn and Cu in water hyacinth, OC,
TN, TP, TK, TCa, Mn, Zn and Cu in paddy waste, OC, TN, TP, TCa and Cu in cow dung,
and OC, TN , TCa, Mn, Zn and Cu in organic mixture were also significantly improved
during vermicomposting of partly decomposed organic materials by P.excavatus.
Similar type of elevations were also reported from the nutrients analysis made in
different vermicomposts obtained from cattle manure (N, P, Fe, Mn, Cu and Zn), paper mill
sludge + cattle manure (N, P, Fe, Mn and Cu), dairy sludge + cattle manure (N, P, Fe, Mn
and Zn) and paper mill sludge + dairy sludge + cattle manure (N, P , Fe, Mn, Cu and Zn)
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after exposure to E.andrei (Elvira et al.,1998), cocoa leaves and areca leaves (OC, N, P, K,
Cu Fe, Zn and Mn) after exposure to E.eugeniae (Chowdappa et al .,1999), municipal
sewage plant waste (TN) after exposure to E.fetida (Masciandaro et al.,2000), sugar cane
trash with press mud (N, P, K, Ca, Mg and Fe) after exposure to P.excavatus
(Ramalingam, 2001), sugar cane trash (N, P, K, Ca, Mg, Fe, Cu and Mn) and sugar cane
trash with cow dung (P, K, Fe, Cu and Mn) after exposure to P.excavatus (Ramalingam and
Thilagar, 2000), press mud (N, P, K, Ca, Mg, Na, Fe and Mn) after exposure to E.eugeniae
(Ramalingam and Ranganathan, 2001), press mud (N, P, K, Mg, Fe and Zn) after exposure to
E.eugeniae (Parthasarathi and Ranganathan, 2002), paddy chaff powder and weed plants
material (N and K) after exposure to L.mauritii (Bakthavathsalam and Geetha, 2004c), rice
straw (OC, N, P, K, Ca ,Mg and Na, OC and N, and OC, N , K , Ca, Mg and Na) after
respectively exposure to P.excavatus, O.phillotti and O.rosea (Vikram Reddy and
Ohkura, 2004), press mud, and sago solid waste + press mud mixture (1:4 and 3:2 ratios)
(N, P , K, Ca and Mg) and sago solid waste + press mud mixture (2: 3 ratio) (OC, N, P, K, Ca
and Mg) after exposure to E.eugeniae (Christy and Ramalingam, 2005b), press mud,
and sago solid waste + press mud mixture (1 : 4, 2 : 3 and 3 : 2 ratios)
(N, P, K, Ca and Mg) after exposure to P.excavatus (Ramalingam and
Christy, 2006), cattle manure mixed with saw dust waste (K) after exposure to P.excavatus
(Meena and Renu, 2007), press mud (N, P and K) after exposure to P.excavatus
(Parthasarathi, 2007), domestic waste (OC, TN, TP and TK) after exposure to P.excavatus
and P.sansibaricus respectively (Suthar and Singh, 2008), fly ash mixed with cow dung
(TN, TP, TK ,TCa, TMg, TZn, TCu, TMn and TFe) after exposure to E.eugeniae
(Venkatesh and Eevera, 2008), green gram waste (N, P , Fe, Zn and Cu) after
exposure to E.eugeniae (Jayaseelan and Bakthavathsalam, 2009b), paddy
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straw waste (N and P) after exposure to E.eugeniae (Subramaniyan and
Bakthavathsalam, 2009), vegetable market waste (OC, N, P , K , Ca, Mg, Zn, Fe, Cu and
Mn) after exposure to L.mauritii (Uthayakumar and Bakthavathsalam, 2009), coir waste +
E.crassipes + cow dung + poultry excreta mixture (1:1:1:1ratio) (OC, P, K, Ca, Mg, S, Zn,
Cu, Fe and Mn) after exposure to E.eugeniae (Bakthavathsalam et al., 2010c), elephant dung
(S and Mn) after exposure to E.eugeniae (Sudha and Bakthvathsalam, 2010) and P.longifolia
leaves (OC, N, P, K, Na, Ca, Mg, S, Zn and Cu) after exposure to E.eugeniae
(Umamaheshwari and Bakthavathsalam, 2010).
The levels of TNa in paddy waste / cow dung and TK in organic mixture after
exposure to L.mauritii, TCa , Fe and Mn in water hyacinth, TNa in paddy waste, TNa,
Mn and Zn in cow dung, and TK and TNa in organic mixture after exposure to
P.excavatus were decreased while vermicomposting the same for
30 days. Similar type of nutrients reduction was also noticed in the levels of
K in cattle manure individually and in combination with paper mill sludge and dairy sludge,
K and Zn in paper mill sludge mixed with cattle manure, and Mn in dairy sludge mixed with
cattle manure after exposure to E.andrei by Elvira et al .(1998), Na and Zn in sugar cane
trash individually and in combinations with press mud after exposure to P.excavatus by
Ramalingam (2001), Ca, Na and Zn in sugar cane trash individually and with cow dung after
exposure to P.excavatus by Ramalingam and Thilagar (2000), K, Ca and Na in rice straw
after exposure to O.phillotti by Vikram Reddy and Ohkura (2004), Na in press mud
individually and in combination with sago solid waste (4 : 1, 3 : 2 and 2 : 3 ratios) after
exposure to E.eugeniae by Christy and Ramalingam (2005b), Na and S in press mud
individually and in combination with sago solid waste (4 : 1, 3: 2 and 2 : 3 ratios) after
exposure to P.excavatus by Ramalingam and Christy (2006), Na and Ca in cattle manure
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mixed with saw dust waste after exposure to P.excavatus by Meena and Renu (2007),
K and Mn in green gram waste after exposure to E.eugeniae by Jayaseelan and
Bakthavathsalam (2009b), K, Fe, Mn and Zu in paddy straw waste after exposure to
E.eugeniae by Subramaniyan and Bakthavathsalam (2009), Na in coir waste mixed with
E.crassipes, cow dung and poultry excreta after exposure to E.eugeniae by Bakthavathsalam
et al .(2010c), and K, Na, Ca, Zn, Cu and Fe in elephant dung after exposure to E.eugeniae
by Sudha and Bakthavathsalam (2010).
The increased levels of micro and macronutrients observed in different vermicomposts
reflect the effective nature of decomposition when the organic materials pass through the gut
of earthworms. This result was in confirmation with the reported results of Edwards and
Bohlen (1996), where they found increased levels of microbial population, microbial activity,
microbial respiration, enzymatic activity and micro and macronutrients of organic
vermicomposts. Similarly Scheu (1987), Mulongy and Bedoret (1989), Parthasarathi and
Ranganathan (1999) and Kalam et al. (2004) have also shown to increase the microbial
population, microbial activity and NPK contents of vermicomposts obtained from different
organic wastes. Previous studies (Parthasarathi and Ranganathan, 1999; Vinotha et al., 2000;
Parthasarathi et al., 2007; Parthasarathi, 2007) have also shown to increase the levels of
NPK, cellulocytic, amylolytic, proteolytic and phosphate solubilizing enzyme activities,
population of nitrifying microbes and microbial activities in the vermicasts obtained from
press mud. Kale (1988) also reported a significant increase in the available NPK in worm
worked cow dung and sheep dung. Similarly, Bano and Suseela Devi (1996) have also
reported increased levels of macro and micronutrients in the vermcomposts obtained from
different organic wastes. Likely Ramalingam (1997) has also noticed increased level of N, P,
K, Ca and Mg in the vermicomposts obtained from individually and in combination with
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different organic wastes such as coir waste, press mud, water hyacinth, farm wastes, farm
yard manure and biogas slurry of cattle dung after using them separately by L.mauritii and
E.eugeniae. Jambhekar (1992) has also noticed a considerable increase in the available NPK
of worm worked wastes than that of original wastes. Haimi and Huhta (1987) have analysed
chemically and compared the nutrient levels in worm worked, wormless and conventional
composts and reported higher level of nutrients in worm worked compost. Bano et al.(1987)
have also analysed the vermicomposts obtained from E.eugeniae worked organic wastes and
suggested the acceleration of mineralization while the food passing through the gut of
earthworms.
The waste materials ingested by the earthworms undergo bio – chemical changes
leading to the production of cast containing assimilated form of plant nutrients and growth
promoting substances formed by the assistance of earthworm’s enzymatic and microbial
activity (Kitturmath et al., 2007).
5.4.3.1 Reasons for TN increase
The enhancement of N observed in the vermicomposts obtained from different organic
materials after exposure to L.mauritii and P.excavatus corroborated with the findings of
earlier reports made by Bouche et al. (1997) and Balamurugan et al.(1999). This
enhancement was probably due to loss of carbon and / or mineralization of the organic matter
containing proteins (Bansal and Kappor, 2000; Kaushik and Garg, 2003) and conversion of
ammonium – nitrogen into nitrate (Suthar and Singh, 2008; Atiyeh et al., 2000c).
Earthworms can boost the nitrogen level in the feeding organic materials during digestion
while passing through gut adding their nitrogenous excretory products, mucus, body fluid,
enzymes, and even through the decaying dead tissues of worms in vermicomposting
subsystem (Suthar, 2007b). The increased mineralization is partly effected through
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earthworm respiration, but mostly through stimulation of microbial activity in earthworm
guts and casts. Mineralization is also increased by the secretion of labile C compounds in
mucus and subsequent alteration of soil structure (Edwards and Bohlen, 1996). The
vermicomposts produced by these earthworms showed a substantial difference in their total
N content, which could be attributed directly to the species – specific feeding preference of
individual earthworm species or the initial nitrogen levels of organic matters used or the
extent of decomposition (Crawford, 1983) and indirectly to mutualistic relationship between
ingested microorganisms and intestinal mucus (Suthar and Singh, 2008). Production of
vermicastings, earthworm dead tissue, nitrogen excretion and stimulated activity of N –
fixing bacteria during composting process would have been responsible for higher N content
in vermicomposts (Daniel and Anderson, 1992).
5.4.3.2 Reasons for TP increase
The availability of P in any vermicompost depends upon the quantity of phosphate
present in the raw organic matters or it can be attributed to the quantities of phosphorus
ingested by earthworms in the organic matter they consume and excreted in their casts. Some
authors believe that the greater release of P from casts is due to enhanced microbial activity
(Lee, 1985; Scheu, 1987). However, others suggest that it is due to increased phosphatase
activity (Lavelle and Martin, 1992).
The enhanced P level in vermicompost suggests phosphorus mineralization during
vermicomposting. The worms during vermicomposting process converted the insoluble P
into soluble forms in their gut with the help of P – solubilizing microorganisms through
phosphatases making them more available to plants (Suthar and Singh, 2008;
Padmavathiamma et al., 2008; Ghosh et al., 1999a). The increased uptake of P by
phosphobacteria could be attributed to its greater P – solubilization potentiality in the
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presence of organic matter (Sharma and Singh, 1971). Further, numerous bacteria are also
responsible for greater P – solubilization (Alexander, 1977). The increase in TP during
vermicomposting is probably due to mineralization and mobilization of phosphorus by
bacterial and faecal phosphatase activity (Edwards and Lofty, 1972). Lee (1992) suggests
that the passage of organic matter through the gut of earthworms results in phosphorus is
converted to forms, which are more available to plants. The release of phosphorus in the
available form is performed partly by earthworm gut phosphatase and further release of P
might be attributed to the P – solubilizing microorganisms present in worm casts (Satchell
and Martin, 1984). Le Bayon and Binet (2006) concluded that the impact produced by
earthworm on P biogeochemical transformations in the soil depends on the close relationship
between the properties of the organic P source and the specific burrowing behaviour and
food preferences of worms.
5.4.3.3 Reasons for TK increase
The increased K level observed in the vermicomposts was probably due to physical
decomposition of organic waste through biological grinding during passage through the gut
coupled with enzymatic activity in worms gut, which may have caused its increase (Rao
et al., 1996). The micro organisms present in the worm’s gut probably converted insoluble K
into the soluble form by producing microbial enzymes (Kaviraj and Sharma, 2003). The
microflora also influences the levels of available potassium in the vermicomposts. Carbonic,
nitric and sulfuric acid production by microorganisms is the major mechanism for
solubilizing the insoluble potassium. The enhanced number of microflora present in the gut
of earthworms might have played an important role in the vermicomposting process and
increased the levels of K2O in the vermicomposts (Kaviraj and Sharma, 2003). The selective
feeding of earthworms on organically rich substances which breakdown during passage
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through the gut, biological grinding, together with enzymatic influence on finer soil particles,
were likely responsible for increased level of different forms of K (Rao et al., 1996). Benitez
et al. (1999) studied that the leacheates collected during vermicomposting process had higher
K concentration. Kaviraj and Sharma (2003) also observed that level of TK was increased
10% by E.fetida and 5% by L.mauritii during vermicomposting process. Suthar (2007b)
suggested that earthworm processed organic waste material contains high concentration of
exchangeable K, due to enhanced microbial activity during the vermicomposting process,
which consequently enhanced the rate of mineralization. Some previous studies also indicate
enhanced potassium content in vermicompost by the end of vermicomposting practice
(Manna et al., 2003; Suthar, 2007c). The increased results obtained in the current study are
similar to those of Delgado et al. (1995), who demonstrated higher potassium concentration
in the end product prepared from sewage sludge.
5.4.3.4 Reasons for TCa increase
The higher Ca content observed in the vermicomposts is attributable to the catalytic
activity of carbonic anhydrase present in the calciferous glands of earthworms generating
CaCO3 while fixing CO2 (Padmavathiamma et al., 2008). It is suggested that gut process
associated with calcium metabolism are primarily responsible for the enhanced content of
inorganic calcium in the worm cast. Similar pattern of calcium enhancement is also well
documented in available literature (Hartenstein and Hartenstein, 1981; Garg et al., 2006b).
5.4.3.5 Reasons for Fe, Na and Mn decrease
Addition of organics might have increased the microbial population and in turn
releasing the chelating agents thereby prevented micronutrients from precipitation, oxidation
and leaching (Bellakki and Badanur, 1997). Micronutrients such as Fe and Cu are required
for hemoglobin and enzyme formation (Lehninger et al., 1996). Further autotrophic bacteria
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obtained their energy from the oxidation of Fe, Cu and ammonia. The significant /
insignificant decrease observed in TNa (L.mauritii and P.excavatus exposed paddy waste and
cow dung), Fe (P.excavatus exposed water hyacinth) and Mn (P.excavatus exposed water
hyacinth and cow dung), may be due to increased utilization of respective elements from the
ingested organic wastes by these earthworms and microbes for their growth (production of
biomass) and reproduction as suggested by Ramalingam and Thilagar (2000). Many workers
have also reported reduction in the levels of Na in vemicomposts obtained from different
organic wastes after exposure to different earthworms (Kale et al., 1994;
Ramalingam, 2001; Ramalingam and Ranganathan, 2001; Vikram Reddy and Ohkura, 2004;
Christy and Ramalingam, 2005; Ramalingam and Christy, 2006; Meena and Rena, 2007;
Bakthavathsalam et al., 2010c and Sudha and Bakthavathsalam, 2010).
5.4.4 C : N ratio
Though a slight increase or decrease was noticed in the C: N ratios of paddy waste,
water hyacinth, cow dung and organic mixture vermicomposts over their partly decomposed
organic materials, but all of them were in the safe range at 20 : 1 as suggested by Edwards
and Lofty (1977). Similar optimum C / N ratios were also reported in the vermicomposts
obtained from sewage sludge after exposure to E.fetida for 18 weeks (8 : 1) by Benitez
et al. (1999), cocoa leaves (14.78 : 1) after exposure to E.eugeniae for 90 days by
Chowdappa et al. (1999), press mud after exposure to E.eugeniae for 30 days (14.1
0.32 : 1 ) by Ramalingam and Ranganathan (2001), sago solid waste with press mud after
exposure to E.eugeniae for 75 days (8.9 0.4 :1) by Christy and Ramalingam (2005b), sago
solid waste with press mud after exposure to P.excavatus for 75 days (10.3 0.04 :1) by
Ramalingam and Christy (2006), cow dung with vegetable market waste after exposure to
E.eugeniae for 25 days (7.57 : 1) by Karthikeyan et al.(2007), domestic waste after exposure
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to P.excavatus (10.40 0.04 : 1) and P.sansibaricus (9.89 0.05 : 1) for 150 days by
Suthar and Singh (2008), and cow dung (13.1 1.71 : 1 ) after exposure to E.fetida for 60
days by Gorakh Nath et al. (2009)
The optimum C : N ratios (around 20 :1 ) observed in the present vermicomposts
could be achieved on the one hand, by combustion of carbon during earthworm’s respiration
and worm gut microbial utilization (Edwards and Bohlen, 1996 ; Suthar, 2007c) and on the
other hand, increase of nitrogen by microbial mineralization of organic matter (Syres
et al., 1979) combined with the addition of worm’s nitrogenous wastes through excretion and
mucus secretion (Dash and Senapati, 1985 ; Curry et al., 1995 ; Talashilkar et al., 1999 ;
Christy and Ramalingam, 2005b ; Suthar, 2007c). The narrow range of C : N ratios observed
in the vermicomposts (present study) reflect the efficient nature of worm’s activity, leading
to accelerated rate of decomposition and mineralization of organic wastes (species specific
activity) there by releasing nutrients rich good quality vermicomposts.
Here, it is a point to note that C/N ratios of initial samples (un decomposed raw organic
materials) were not determined and hence it is not possible to assess the extent of
decomposition during vermicomposting. However the initial (before composting) C/N ratios
reported in different organic materials such as cow dung (86.2 2.40 : 1), buffalo dung
(92.0 1.60 :1), goat dung (93.0 0.13 : 1), sheep dung (85.8 0.8 : 1) and horse dung
(132.0 1.20 : 1) by Gorakh Nath et al. (2009), and cow dung (89.4 : 1), buffalo dung
(93.0 : 1), donkey dung (97.1 : 1), sheep droppings (88.9 : 1), goat droppings (93.5 : 1) and
camel dung (116.1 : 1) by Garg et al. (2005a) were relatively very high when compared to
their vermicomposts. According to Senesi (1989) declined in C: N ratio to less than 20
which indicates an advance degree of organic matter stabilization and reflects a satisfactory
degree of organic matter mineralization. Suthar (2008) also reported that the C : N ratio of
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any organic substrate reflects the extent of organic waste mineralization and stabilization
during the process of decomposition.
The C : N ratio is the main criteria that determines the quality of compost /
vermicompost since plants cannot assimilate mineral nitrogen unless the C/N ratio is 20 : 1 or
lower (Edwards and Lofty, 1977), and this ratio is also an indicative of acceptable maturity
of compost (Morais and Queda, 2003). Higher C/N ratio indicates slow degradation of
substrate (Haug, 1993), but lower one reflects the higher degree of mineralization /
decomposition of organic materials. Lower C/N ratios observed in the vermicomposts of
water hyacinth, paddy waste, cow dung and organic mixture obtained after exposure to
L.mauritii and P.excavatus for 30 days (present study) revealed active participation of
earthworms in the process of mineralization during vermicomposting process (Suthar and
Singh, 2008 ; Padmavathiamma et al ., 2008).
5.5 Cultivation of chilli plant using vermicomposts
The control chilli plants that are raised in soil medium (earthworm exposed or
unexposed) showed over all poor growth and yield values (Tables 30 – 33) over the same
plants raised in other PSR doses of partly decomposed, L.mauritii exposed and P.excavatus
exposed organic materials. But the mean values observed in the experimental plants grown in
different organic matters revealed a differential and dose dependent effect with lesser values
in lower doses and higher values in higher doses. However the plants that are raised in
different doses of partly decomposed organic materials showed relatively lesser growth and
yield values over the plants raised in earthworm exposed organic materials. Similarly of the
two earthworm exposed organic materials used, the growth and yield values of chilli plants
raised in L.mauritii exposed organic materials (all doses) were relatively very high when
compared to the plants raised in P.excavatus exposed organic materials.
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From the above results it is proved that the application of vermicomposts has a
positive role on the growth and yield of chilli plant according to the doses and organic
materials applied. This observation falls in line with many reported results already made in
other plants using different vermicomposts obtained from different sources. There are
experiments in which plants have been grown in pots with earthworms or their casts or
vermicompost, where an increase in plant growth occurred. Kale and Bano (1986) found that
the vegetative growth of plants was influenced by E.eugeniae worm cast in a better way than
chemical fertilizers. Line (1994) reported that vermicomposted mixture of wood waste and
seastar waste showed an excellent growth of tomatoes and lettuces. Kale (1994) has also
recorded on excellent growth and yield of cereals, pulses, oilseeds, spices, vegetables, fruits,
ornamental plants, cash crops and plantation crops after administered with vermicompost.
Arulmurugan (1996) has studied the effect of vermicompost on the growth, yield, protein and
oil content of soya bean and recorded an increase in plant height, root length, root volume,
number of seeds produced, protein and oil content of seeds together with increased uptake of
NPK. Vadiraj et al. (1996) noticed pronounced influence of vermicompost on the growth and
yield of turmeric plant.
Like the present observation, Ramalingam (1997) has also noticed a differential effect
on the growth parameters of tomato after administered with organic manures (cattle dung,
farm yard manure and press mud) and vermicomposts (obtained from a mixture of farm
waste and press mud, water hyacinth and press mud, and water hyacinth and press mud
slurry) and found an enormous increase in the growth parameters of vermicomposts treated
plants over organic manure treated plants. Senapati (1993) reported that the emergence of
tomato seedlings in vermicompost is much better than in the recommended commercial
potting compost. Madhukeshwara et al. (1996) also reported that vermicompost increased the
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germination efficiency and growth of tomato and suggested that vermicompost can be used
as a ideal and more economical organic substitute for raising healthy nurseries which is a
constraint before transplantation in the field. The mechanisms through which plant growth is
stimulated by vermicompost or worm cast are not clear. However, it is believed that the
stimulating effect observed in the plant growth/ yield could be due to synergic action of
several factors, but the major claim goes to microbial metablites – the growth regulators
present in the vermicompost as suggested by Tomati et al. (1987; 1988).
On the basis of above observations it is suggested that the synergic action of factors
such as presence of growth regulators (Tomati et al., 1985; 1988) and substances having
stimulatory effect on protein and photosynthesis (Tomati et al., 1985), enrichment of organic
carbon, micro and macro nutrients, vitamins, enzymes, antibiotics and microflora
(Bhawalkar, 1991; Bano and Suseela Devi, 1996; Ramalingam, 1997), humic acids and
humic substances (Phoung and Tichy, 1976) and polysaccharides (Tomati and Galli, 1995)
seems to be responsible for the accelerated growth observed in the chilli plants administered
with different vermicomposts.
Similarly, many reports have been made in the white radish
plant cultivated in paddy chaff vermicompost and weed plants vermicompost
by Bakthavathsalam and Geetha (2004c), green gram waste vermicompost by Jayaseelan
and Bakthavathsalam (2009b), paddy straw waste vermicompost by Subramaniyan and
Bakthavathsalam (2009), vermicomposts obtained from the organic mixtures containing coir
waste, E.crassipes, cow dung and poultry excreta, and coir waste, water lily, goat droppings
and poultry excreta respectively by Bakthavathsalam et al. (2010c ; d), partly decomposed
water hyacinth by Mathialagan and Bakthavathsalam (2010), and partly decomposed
P.longifolia leaves and cow dung by Umamaheswari and Bakthavathsalam (2010).
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Jeyabal and Kuppuswamy (2001) have also studied direct and residual effect of
integrated application of 50 % organic N (supplied from vermicomposts of different organic
matters such as bio digested slurry, coir pith, weeds, cow dung and press mud), 50%
inorganic N (fertilizers) and bio fertilizers (Azospirillum and Phosphobacteria) on the growth
and yield of rice and black gram plants raised in field and recorded a grain yield respectively
to the tune of 12.2 and 19.9% higher than that of 100% inorganic N treated plants without
affecting the soil health. A significant increase was noticed in the growth and yield of black
gram (Vigna mungo) and ground nut (Arachis hypogace) plant raised in field using
E.eugeniae exposed press mud (vermicast) and NPK by Parthasarathi and
Ranganathan (2002). Bakthavathsalam and Deivanayaki (2007) have also noticed a
significant increase in the growth and yield of black gram plant raised in commercial
vermicompost mixed with or without rhizobium. Uthayakumar and Bakthavathsalam (2009)
have also noticed an excellent improvement over control in the production of black gram
plants administered with vegetable market waste vermicompost.
Gondek and Filipek – Mazur (2003) and Gondek (2008) have also noticed better
growth and yield of maize, winter rape, sunflower and oat plants raised in pots and field
respectively administered with vermicomposts obtained from different organic mixtures
(tannery sludge mixed with sawdust or card board or wheat straw) after exposure to E.fetida.
Vikram Reddy and Okhura (2004) have also noticed increased growth of sorghum (Sorghum
bicolor) raised in rice straw vermicompost through pot cultivation. Sinha et al.(2005) have
also noticed good growth and yield of mulberry leaves after the application of
vermicomposts obtained from different organic matters such as cow dung with or without
silk worm rearing wastes, farm refuse, weeds, mulberry leaves. Bisht et al. (2006) have also
noticed higher growth of maize, barley and wheat plants raised in earthworm treated grass,
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maize and wheat waste materials through pot as well as field trails. Similarly a significant
increase was noticed in the growth and yield of spinach (Spinacia loeracea) plant raised
through bag cultivation in cattle manure vermicompost obtained after two months exposure
to E.fetida by Peyvast et al.(2008). Ansari (2008) has also noticed a significant increase in
the yield of spinach, onion and potato plants raised in vermicomposts and vermiwash
obtained from paddy straw and cattle dung materials after exposure to P.excavatus and
L.mauritii through field cultivation. Muruganandam and Bakthavathsalam (2009) have also
noticed a significant increase in the growth and yield of chilli plant cultivated in different
doses of compost of cabbage waste and cow dung.
Vermicomposts produced by different earthworms under various decaying organic
matter have been claimed to be useful as plant grow media for wide range of plants (Edwards
and Burrows, 1989). The application of vermicompost was not only better for seedling
emergence but also for the growth of transplanted plants, and it is often better than the
commercial plant – growth media (Vikram Reddy and Ohkura, 2004). The earthworm casts
and vermicompost influenced the development of plants through stem elongation, root
initiation and root bio mass, which suggest the linkage between biological effects of
vermicompost and microbial metabolites that influence the plant growth and development
(Tomati et al ., 1988). Kale et al. (1992), Zhaw Shi-wei and Houng Fu-Zhen (1992),
Kulkarni et al. (1996), Edwards and Bohlen (1996), Sevugaperumal et al. (1998), Atiyeh
et al.(1999), Buckerfield et al. (1999) and Garg and Bhardwaj (2000) have demonstrated the
application of vermicomposts to increase the growth and yield of paddy, wheat, maize,
tomato, rose, citrus, guava, curry leaf, turmeric, ornamental plants, cash crops, plantation
crops, cereals, radish, pulses, oil seeds, spices, vegetables, fruits and sorghum and also to
improve the physical and also to chemical characteristics of the soil.
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The fertilizing value of vermicompost and its beneficial effect on plant growth have
been related to the presence of active mineral nutrients (Masciandaro et al., 1997), microbial
and enzyme activities (Edwards and Bohlen, 1996) and growth regulators like gibberllins,
cytokinins and auxins with phytohormonal action (Tomati and Galli, 1995). Humic
substances have been found to possess phytohormonal properties which influence the growth
of both root and shoot (Sequi, 1986) and stimulate the synthesis of de novo invertase – an
enzyme closely associated with plant growth (Vaughan and Malcolm, 1979). Large leaf area
index reflects photosynthetic ability of the plant and nitrogen content of leaves and its
enhancement was responsible for the higher growth and yield of plants (Libunao, 1986).
Ghosh et al. (1999b) reported that integration of vermicompost with inorganic fertilization
tended to increase the yield of crops such as potato, rape seed, mulberry and marigold over
that with traditional compost prepared from the same substrate. A field trial conducted on
upland rice (var TRC – 82 – 251) using different doses of vermicompost revealed significant
increase in both grain and straw yield coupled with improvement in soil aggregation, water
holding efficiency and nutrient uptake over control or even NPK treated plants
(Bhattacharjee et al., 2001). Vermicompost along with judicious use of chemical fertilizers
will not only bring down the cost of cultivation but also present unique opportunities for
sustainable agriculture (Bhattacharjee et al., 2001).
Application of 100 per cent N as organic forms (compost or vermicompost)
significantly reduced the bulk density due to the improvement of soil aggregation and
structure which directly influence the bulk density of soil (Jegadeswari, 1997). Water holding
capacity was favourably increased even up to 48.6 % from its base point of 35.8% after the
application of 100 per cent N through vermicompost as a result of higher pore space, low
bulk density and favourable soil structure (Logsdon and Linden, 1992). Application of
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different organic N sources had significantly increased the nutrient availability and microbial
population (Kannan et al., 2005). Due to higher amount of growth promoting substances,
vitamins, enzymes and microbial population present in the vermicompost increased the
production of root biomass there by absorbing essential nutrients available in the soil.
Considering the above findings in perspective, organic farming through application of
different organic sources favourably influenced the soil’s physical, chemical and biological
fertility over the application of inorganic fertilizer, which in turn paved the way for better
quality and good crop yield.