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.