Development of a water hyacinth based vermireactor using an epigeic earthworm Eisenia foetida

Bioresource Technology 98 (2007) 2605–2610

Development of a water hyacinth based vermireactor using an epigeic earthworm Eisenia foetida Renuka Gupta, Praveen Kumar Mutiyar, Naresh Kumar Rawat, Mahender Singh Saini, V.K. Garg ¤ Department of Environmental Science and Engineering, Guru Jambheshwar University of Science and Technology, Hisar 125001, India Received 18 July 2006; received in revised form 9 September 2006; accepted 12 September 2006 Available online 27 October 2006

Abstract The aim of this work was to investigate the potential of water hyacinth (WH) spiked with cow dung (CD) into vermicompost. Five vermireactors containing WH and CD in diVerent ratios, were run under laboratory conditions for 147 days. The maximum worm growth was recorded in CD alone. Worms grew and reproduced favourably in 25% WH + 75% CD feed mixture. Greater proportion of WH in feed mixture signiWcantly aVected the biomass gain, hatchling numbers and numbers of cocoons produced during experiments. In all the vermireactors, there was signiWcant decrease in pH, TOC and C:N ratio, but increase in TKN, TK and TAP at the end. The heavy metals content in the vermicomposts was lower than initial feed mixtures. The results indicated that WH could be potentially useful as raw substrate in vermicomposting if mixed with up to 25% in cow dung (on dry weight basis). © 2006 Elsevier Ltd. All rights reserved. Keywords: Water hyacinth; Cow dung; Biomass; Reproduction; Nitrogen; C:N ratio; Phosphorus; Heavy metal; Cocoon

1. Introduction Water hyacinth (Eichhornia crassipes (Mart) Solms – Laubach; family: Pontederiaceae) has been listed as most troublesome weed in aquatic systems. It is a severe environmental and economical problem in many tropical and subtropical parts of the world. It forms dense mats that prevent river traYc, block irrigation canals, interfere with hydel power projects and destroy rice Welds. As water hyacinth decays, there is a sharp increase in nutrient levels in water body, which ultimately creates the problem of eutrophication in aquatic system. Chemical control of water hyacinth with herbicides like 2,4 -D, dalapan, diquat and glyphosate was considered most eVective but it resulted in water pollution (Singh and Gill, 1997). The stringent and rigid standards for pesticide use in water bodies and public consciousness also call for some alternate technology for

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aquatic weed management. Abbasi and Ramasamy (2001) have reported that water hyacinth has successfully resisted chemical, physical, biological or hybrid means used to eradicate it. The only accepted use of water hyacinth is in treating the biodegradable wastewaters (Tchobanoglous and Burton, 1991). The Wnal disposal of water hyacinth used in wastewater treatment is still an unsolved problem (Gajalakshmi et al., 2002). Therefore, a novel technology with ecological sound and economically viable is urgently required to solve the problem of aquatic weed disposal and management. It has been well established that epigeic forms of earthworms can hasten the composting process to a signiWcant extent with production of a better quality of compost as compared with those prepared through traditional composting methods (Ndegwa and Thompson, 2001). Use of earthworms for waste management, organic matter stabilization, soil detoxiWcation and vermicompost production have been well documented in literature (Bansal and Kapoor, 2000; Kaushik and Garg, 2003; Garg and Kaushik, 2005; Suthar, 2006b). The eVect of water hyacinth on

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life cycle of diVerent earthworms has been documented by other workers (Gajalakshmi et al., 2001, 2002). The bibliographic analysis has shown that precomposted WH was more preferred by Eudrilus eugeniae than fresh WH and blending of CD with WH has a signiWcant positive impact on the vermicompost output (Gajalakshmi et al., 2002). However, there seems to be a paucity of data on the fertilizer value of the end product (vermicompost) produced by using water hyacinth as feed stock. The aim of this study was to explore the potential of Eisenia foetida in diVerent vermireactors, prepared with water hyacinth and cow dung mixed in diVerent ratios, to achieve the goal of value-added biofertilizer with maximum nutrient recovery and least worm mortality. 2. Methods 2.1. Water hyacinth (WH), cow dung (CD) and E. foetida Fresh water hyacinth plants were collected from a natural wetland infested with water hyacinth. The soil particles/ mud adhered with the roots and leaves of the plants were washed with running water. The plants were cut into pieces of 2–3 cm for the present study before mixing with CD. The main physico-chemical characteristics of WH were: moisture (%), 92.8 § 1.30; ash content (g kg¡1), 417 § 3.6; pH (1:10 ratio), 8.1 § 0.06; TOC (g kg¡1), 338 § 2.1; TKN (g kg¡1), 9.5 § 0.3; C:N ratio, 36.0 § 1.63; TK (g kg¡1), 9.7 § 0.7; TAP (g kg¡1), 5.4 § 0.5; total-Fe (mg kg¡1), 1640 § 59; total-Cu (mg kg¡1), 312 § 28; total-Cd (mg kg¡1), 1.36 § 0.27; total-Cr (mg kg¡1), 41.18 § 0.64; total-Pb (mg kg¡1), 67 § 5.7; and total-Zn (mg kg¡1), 640 § 33. Fresh CD was procured from an intensively live stocked farm at Hisar, India. The main physico-chemical characteristics of CD were: moisture (%), 79.4 § 7.35; ash content (g kg¡1), 195 § 10.4; pH (1:10 ratio), 8.2 § 0.06; TOC (g kg¡1), 467 § 6.0; TKN (g kg¡1), 7.7 § 0.3; C:N ratio, 60.6 § 2.66; TK (g kg¡1), 4.8 § 0.1; TAP (g kg¡1), 3.3 § 0.3; total-Fe (mg kg¡1), 282 § 36; total-Cu (mg kg¡1), 42 § 4.4; total-Cd (mg kg¡1), 0.53 § 0.10; total-Cr (mg kg¡1), 10.3 § 0.43; total-Pb (mg kg¡1), 1.82 § 0.21 and total-Zn (mg kg¡1), 317 § 47. Earthworms used in the experiment were picked from stock culture maintained in laboratory.

0.50 kg CD + 0.50 kg WH + earthworm; vermireactor 4: 0.25 kg CD + 0.75 kg WH + earthworm; vermireactor 5: 1.00 kg WH + earthworms. These mixtures were turned manually every 24 h for 21 days in order to eliminate volatile gases potentially toxic to earthworms. After 21 days, 20 adult individuals of E. foetida (weighing between 250 and 400 mg) were introduced into each vermireactor. The moisture content was maintained at 70 § 10% of water holding capacity by periodic sprinkling of an adequate quantity of distilled water. All the containers were kept in the dark under identical ambient conditions (room temperature 25 § 3 °C, relative humidity 60–80%). The experiments were replicated thrice for each feed mixture. At the end of experiment (after 147 days), the substrate material in each vermireactor was turned out. The earthworms, hatchlings and cocoons were separated from the feed by hand sorting, after which they were counted and weighed after washing with water and dried by paper towels. The worms were weighed with full gut. No correction has been applied for gut content. A sample of Wnal compost was collected from each container and air-dried at room temperature. Homogenized samples of Wnal compost were ground in a stainless steel blender, stored in airtight plastic vials for further chemical analysis. 2.3. Chemical analysis The samples were used on dry weight basis for chemical analysis that was obtained by oven drying the known quantities of material at 110 °C. The pH was determined using a double distilled water suspension of each vermicompost in the ratio of 1:10 (w/v). Total organic carbon (TOC) was measured using the method of Nelson and Sommers (1982). Total Kjeldhal nitrogen (TKN) was determined by following Bremner and Mulvaney (1982) procedure. Total available phosphorus (TAP) was analyzed using the colorimetric method (Bansal and Kapoor, 2000). Total potassium (TK) was determined after digesting the sample in diacid mixture [conc. HNO3:conc. HClO4, 4:1, v/v] (Bansal and Kapoor, 2000) by Xame photometer. Total-Fe, Cu, Cd, Cr, Pb and Zn were determined by atomic absorption spectrophotometer (AAS) [GBC 932, GBC ScientiWc Equipment Ltd., Australia] after digestion of the sample with conc. HNO3:conc. HClO4 (4:1, v/v) (Bansal and Kapoor, 2000).

2.2. Experimental design 2.4. Statistical analysis In Wve bench-scale vermireactors (vol. 10 L, diameter 40 cm, depth 12 cm), shredded WH was mixed with CD in diVerent ratios. One kg of feed mixture (on dry weight basis) was put in each circular plastic vermireactor. All the CD and WH quantities were used on dry weight basis that were obtained by drying known quantities of material at 110 °C to constant mass in hot air oven. The composition of the CD and WH in diVerent vermireactors is given below: vermireactor 1: 1.00 kg CD + earthworm (Control); vermireactor 2: 0.75 kg CD + 0.25 kg WH + earthworm; vermireactor 3:

One-way ANOVA was used to analyze the signiWcant diVerence between diVerent reactors for observed parameters. Tukey’s t-test also performed to identify the homogeneous type of the reactors for their diVerent chemical properties and earthworm growth parameters i.e. individual weight, earthworm weight gain, individual growth rate, total cocoons numbers, cocoon production rate, etc. The probability levels used for statistical signiWcance were P < 0.05 for the tests.

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3. Results and discussion 3.1. Growth and reproduction of E. foetida in diVerent reactors No mortality was observed in any feed mixture during the study period. In our experiments, all the wastes were precomposted for 21 days and during this period all the toxic gases produced might have been eliminated. It is established that precomposting is essential to avoid the earthworm mortality (Kaushik and Garg, 2003). Table 1 shows the values obtained for diVerent growth and reproduction parameters in E. foetida over the experimental period. The highest biomass production was in vermireactor 1 and the lowest in the vermireactor 5. The biomass production was signiWcantly (P < 0.05) decreased with increasing percentage of water hyacinth in the vermireactors. E. foetida could not reproduce in vermireactor 5. The mean biomass produced was 1.45, 2.81, 3.68 and 29.27 times lesser in vermireactors 2, 3, 4 and 5 than vermireactor 1. Maximum (859 § 28.7) and minimum (189 § 34.6) number of hatchlings were found in vermireactor no. 1 and no. 4, respectively.. However, hatchlings were not observed in vermireactor 5. It was clear that hatchling numbers recorded in vermireactor 1 was statistically diVerent (P < 0.05) than by other reactors studied. There was a consistent pattern of number of residual cocoons to be decreased with increasing proportion of water hyacinth in diVerent feed mixtures. No residual cocoon in vermireactor 5 was noted. The maximum numbers of residual cocoons were observed in vermireactor 1. However, residual cocoon numbers did not show statistically signiWcant diVerent among vermireactors 2, 3 and 4 (P < 0.05). Average biomass production per unit of the feed mixture was signiWcantly (P < 0.05) higher in vermireactor 1 than that of other treatments (Table 1). The diVerence between biomass and cocoon production in diVerent vermireactors could be related to the biochemical quality of the feed, which was one of the important factors in determining onset of cocoon production (Flack and Hartenstein, 1984). Recently, Suthar (2006b) summarized that except to the chemical properties of waste, the microbial biomass and decomposition activities during vermicomposting were also

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important. Micro-Xora played an important role in earthworm nutrition and growth. Better growth and cocoon production on beddings containing plant origin wastes could be due to great microbial biomass and activities and also due to more availability of nutrients. On the basis of present results, it was concluded that feed mixture containing 25% WH could be a suitable growth medium for E. foetida production (Table 1). Higher percentage of WH in the feed mixture signiWcantly reduced the biomass production, number of hatchlings produced, and residual number of cocoons. This might be due to the fact that higher proportion of WH in the feed mixture made it harder and more tensile, which was not easily utilized by the earthworms (Gajalakshmi et al., 2002). The feed with higher proportion of WH might not have suYcient amount of easily metabolizable organic matter and non-assimilated carbohydrates which could be essential for the growth and reproduction of the earthworms (Edwards, 1988). Gajalakshmi et al. (2005) showed that 100% water hyacinth as feed was not preferred by Eudrilus eugeniae, whereas addition of cow dung (t14% CD) had a positive impact on biomass gain and hatchling production. Manna et al. (2003) also reported the addition of farmyard manure in 1:1 ratio in the leaf litter of Tectona grandis, Madhuca indica and Butea monosperma during vermicomposting employing diVerent earthworm species, viz., E. foetida, Perionyx excavatus and Dicogaster bolaui. Suthar (2006b) studied the vermicomposting of crop residues and farmyard manure mixed with some animal dung under laboratory conditions. DiVerent growth and reproduction patterns of P. excavatus in vermibeds were possibly related to the concentrations of polyphenols and related substances presented in plant-derived waste materials. 3.2. Physico-chemical changes in diVerent vermireactors There were little changes in the pH of feeds (Table 2). The pH decreased from alkaline to acidic or neutral (6.5 § 0.1–7.3 § 0.2). Others workers have also reported similar observations (Mitchell, 1997; Gunadi and Edwards, 2003; Ndegwa et al., 2000; Atiyeh et al., 2000). The pH shift towards acidic conditions was attributed to mineralization

Table 1 Total no. of hatchlings, residual cocoons and biomass produced in CD + WH fed vermireactors (n D 3; mean § SE) Vermireactor no.

Initial biomass of worms (g)a

Final biomass of worms (g)b

No. of hatchlings

No. of residual cocoons

Average biomass produced (mg day¡1)

Biomass produced per unit waste (mg g¡1)

1 2 3 4 5

5.27 § 0.14a 6.62 § 0.27b 8.16 § 0.13c 5.90 § 0.14ab 6.21 § 0.19b

96.3 § 2.73d 69.5 § 2.73c 40.6 § 3.94b 30.6 § 2.42b 9.32 § 0.21a

859 § 28.7e 691 § 38.1d 402 § 27.4c 189 § 34.6b 0 § 0.0a

348 § 36.6c 266 § 23.4bc 167 § 29.6b 135 § 32.8ab 0 § 0.0a

619.1 § 17.9d 428.0 § 17.9c 220.3 § 27.4b 168.2 § 16.8b 20.8 § 0.45a

91.0 § 7.0d 63.1 § 4.6c 32.4 § 7.0b 24.7 § 4.3b 3.1 § 0.2a

The experiment was terminated on day 147. Mean value followed by diVerent letters is signiWcantly diVerent (ANOVA; Tukey’s test, P < 0.05). a Biomass of 20 earthworms. b Biomass of parents + hatchlings.

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Table 2 Physico-chemical characteristics of initial feed mixture and vermicompost obtained from diVerent vermireactors Vermireactor no.

pH

TOC (g kg¡1)

Ash content (g kg¡1)

Initial physico-chemical characteristics of initial feed mixture in diVerent vermireactors 1 8.2 467 195 2 8.1 435 250 3 8.2 403 306 4 8.0 370 362 5 8.1 338 417

TKN (g kg¡1)

TK (g kg¡1)

TAP (g kg¡1)

a

7.7 8.2 8.6 9.1 9.5

4.8 6.0 7.3 8.5 9.7

Final physico-chemical characteristics of vermicompost obtained from diVerent vermireactorsb (mean § SE, n D 3) 1 6.9 § 0.1b 139 § 3.76a 760 § 6.5b 20.2 § 0.9a 2 7.1 § 0.17b 167 § 5.46a 711 § 9.4b 21.0 § 0.8a 3 7.0 § 0.2b 151 § 10.2a 742 § 18.1b 18.0 § 0.6a 4 6.5 § 0.1b 220 § 18.7b 621 § 32.4a 20.8 § 1.1a 5 7.3 § 0.2b 244 § 8.62b 580 § 19.9a 19.9 § 0.9a

3.3 3.8 4.4 4.9 5.4

9.5 § 0.21b 11.7 § 0.24c 8.1 § 0.15a 8.3 § 0.44a 8.4 § 0.08a

7.07 § 0.12a 7.30 § 0.3a 6.8 § 0.14a 10.2 § 0.21b 11.8 § 0.46b

a The initial physico-chemical characteristics of feed mixtures given in the table have been calculated based upon the percentage of CD and WH mixed in diVerent vermireactors. b Mean value followed by diVerent letters is signiWcantly diVerent (ANOVA; Tukey’s test, P < 0.05).

of the nitrogen and phosphorus into nitrites/nitrates and orthophosphates; bioconversion of the organic material into intermediate species of organic acids (Ndegwa et al., 2000). It has also been reported that diVerent substrates could result in the production of diVerent intermediate species and diVerent wastes showed a diVerent behavior in pH shift. Haimi and Hutha (1986) postulated that lower pH in the Wnal vermicomposts might have been due to the production of CO2 and organic acids by microbial activity during the process of bioconversion of diVerent substrates in the feed given to earthworms. TOC reduction in vermireactor 1 was signiWcantly higher (P < 0.05) than vermireactors 4 and 5. TOC reduction was inversely related to the water hyacinth content in the vermireactor. This Wnding was similar to that found by Kaviraj and Sharma (2003), who reported 45% loss of carbon during vermicomposting of municipality, or industrial wastes. Elvira et al. (1996) have attributed this loss to the presence of earthworms in the feed mixtures. Suthar (2006a) reported that earthworms promoted such microclimatic conditions in the vermireactors that increased the loss of TOC from substrates through microbial respiration. Ash content of the vermicompost from all the vermireactors was higher than initial feed mixture (Table 2). The ash content had increased in the range of 16.3–56.5%. The vermicomposts whose substrates had lesser percentage of water hyacinth had more ash content. Increase in ash content could be attributed to the enhanced mineralization in the presence of earthworms. The TKN content of WH was higher than CD (Section 2.1), hence, the TKN content of WH containing feed mixtures was higher than CD alone. The initial TKN content of the feed mixtures was in the range of 7.7–9.5 g kg¡1 (Table 2). Vermicomposting resulted in signiWcant increase in the TKN in diVerent vermireactors. Total nitrogen (TKN) content increased in the range of 9.0–12.75 g kg¡1 in diVerent vermireactors (Table 2). The diVerence in the TKN content of the vermicomposts obtained from diVerent vermireactors was not signiWcant (P < 0.05). This shows that the percent-

age of WH in the initial feed mixture have no impact on the Wnal TKN content of the vermicompost. The Wnal TKN content in vermicompost is dependent on the initial nitrogen present in the feed material and the degree of decomposition (Crawford, 1983). According to Viel et al. (1987) losses in organic carbon might be responsible for nitrogen addition. Addition of nitrogen in the form of mucus, nitrogenous excretory substances, growth stimulating hormones and enzymes from earthworms has been reported (Tripathi and Bhardwaj, 2004; Suthar et al., 2005). These nitrogen rich substances were not originally present in feed and might have contributed additional nitrogen content. Initial TAP content of WH was slightly higher than CD (Section 2.1), which resulted in more TAP in WH containing feed mixtures than vermireactor no. 1. The initial TAP content of the feed mixtures was in the range of 3.3–5.4 g kg¡1 (Table 2). Final TAP was higher than initial and was the range of 6.82–11.77 g kg¡1 (Table 2). The increase in TAP was in the range of 2.42–6.37 g kg¡1 in diVerent vermireactors. The Wnal TAP content in vermireactor no. 4 and 5 was signiWcantly (P < 0.05) higher than vermireactor no. 1, 2 and 3. Ghosh et al. (1999) have reported that vermicomposting can be an eYcient technology for the transformation of unavailable forms of phosphorus to easily available forms for plants. It is well established that the release of phosphorous in available form is partly by earthworm gut phosphatases (Le Bayon and Binet, 2006), and further release of P Table 3 Changes in C:N ratio of CD + WH fed vermireactors during vermicomposting Vermireactor Time (days) no. 0 21

42

63

84

105

1 2 3 4 5

42.7c 42.6c 36.7b 29.5a 28.2a

31.7c 31.4c 27.8b 23.8a 26.5b

20.6b 21.8b 23.6b 15.9a 24.3b

13.7a 8.6a 6.9a 19.3c 11.8b 8.0a 16.7b 9.5a 8.4a 13.5a 12.7b 10.6b 16.3b 12.4b 12.3b

60.6c 56.7c 47.2b 39.5a 36.0a

54.3c 50.7c 44.5b 35.8a 31.4a

126

Mean value followed by diVerent letters is signiWcantly diVerent.

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Table 4 Heavy metal content (mg kg¡1) in the initial feed mixtures and Wnal vermicompost produced in CD + WH fed vermireactors Vermireactor no.

Total-Fe

Total-Cu

Heavy metal content in initial feed mixture in diVerent vermireactorsa 1 282 42 2 622 110 3 961 177 4 1301 245 5 1640 312

Total-Cd

Total-Cr

Total-Pb

Total-Zn

0.53 0.74 0.95 1.15 1.36

10.3 18.0 25.7 33.5 41.2

1.82 18.12 34.41 50.71 67.0

317 398 479 559 640

1.04 § 0.21a 6.8 § 1.86a 9.5 § 2.99a 22.4 § 3.70b 26.9 § 2.68b

212 § 12.5a 314 § 49.4a 376 § 49.3a 442 § 64.8a 428 § 55.0a

Heavy metal content in vermicompost obtained from diVerent vermireactorsb (mean § SE, n D 3) 1 243 § 17.9a 27 § 3.8a 0.42 § 0.12a 10.2 § 1.94a 2 272 § 95.9a 56 § 16.6a 0.47 § 0.11a 13.9 § 1.80ab 3 314 § 48.7a 93 § 8.6ab 0.51 § 0.06a 16.7 § 2.69ab 4 618 § 29.5b 178 § 20.6bc 0.53 § 0.22a 21.5 § 3.79ab 5 1227 § 64.0c 228 § 41.8c 0.57 § 0.12a 24.2 § 3.73b

a The initial physico-chemical characteristics of feed mixtures given in the table have been calculated based upon the percentage of CD and WH mixed in diVerent vermireactors. b Mean value followed by diVerent letters is signiWcantly diVerent (ANOVA; Tukey’s test, P < 0.05).

may be by P-solubilizing microorganisms in casts (Vinotha et al., 2000). According to Lee (1992) if the organic materials pass through the gut of earthworms then some of phosphorus being converted to such forms that are available to plants. Increase in TAP was attributed to direct action of worm gut enzymes and indirectly by stimulation of the microXora. Initial TK content of WH was almost double than CD (Section 2.1) and hence initial TK content increased in the initial feed mixtures. The initial TK content of the initial feed mixtures was in the range of 4.8–9.7 g kg¡1 (Table 2). Final TK was higher than initial and was the range of 8.12–11.7 g kg¡1 (Table 2). Maximum TK content (11.7 g kg¡1) was in the vermicompost obtained from vermireactor no. 2 which was signiWcantly (P < 0.05) higher than TK content of the vermicomposts from other vermireactors. Similarly Delgado et al. (1995) have reported higher TK content in the vermicomposts prepared while using sewage sludge as feed mixture. Suthar (2006b) suggested that earthworm processed waste material contains high concentration of exchangeable K, due to enhanced microbial activity during the vermicomposting process, which consequently enhances the rate of mineralization. In contrast Orozco et al. (1996) have reported a decrease in TK in coVee pulp waste after vermicomposting. These diVerences in the results can be attributed to the diVerences in the chemical nature of the initial feed mixtures (Garg et al., 2006). The C:N ratio is used as an index for maturity of organic wastes. We found that it decreased with time in all the vermireactors (Table 3). Initial C:N ratio was in the range of 60.6–36.0. Initial C:N ratio was lesser in those feed mixtures which had higher percentage of WH. Initial C:N ratio of vermireactor no. 1 and 2 were not signiWcantly diVerent (P < 0.05). Where as the initial C:N ratios of remaining vermireactors were signiWcantly diVerent (Table 3). Final C:N ratios were in the range of 12.3–6.9. The Wnal C:N ratios of vermireactor no. 1, 2 and 3 were not signiWcantly (P < 0.05) diVerent. The loss of carbon as carbon dioxide in the process of respiration and production of mucus and nitroge-

nous excrements enhance the level of nitrogen which lower the C:N ratio (Senapati et al., 1980). Water hyacinth was capable of accumulating large quantities of heavy metals from the water (Ingole and Bhole, 2003). Hence, the composts made from WH might contain higher concentrations of heavy metals. Keeping this in view, heavy metal content of the vermicompost obtained from diVerent feed mixtures was quantiWed. Results showed that heavy metals content in WH was several time higher than CD. As a result of this, increasing percentage of WH in feed material resulted in higher heavy metal content in the feed mixtures (Table 4). A comparison of the results showed that heavy metal content in the vermicomposts was slightly lesser than in the initial feed mixtures. The decrease in heavy metal concentration could be related to leaching of the cations by excess water drainage (Garg and Kaushik, 2005), or accumulation by the earthworm. Heavy metal content in raw WH could be a limitation in the use of WH for vermicomposting. To make the vermicomposting of WH realistic, the heavy metal content in raw WH should always be analyzed before its use. 4. Conclusions From the results it was concluded that if WH was mixed with up to 25% in CD (dry weight), the vermicompost quality was not aVected; but a higher percentage of WH in the feed mixture retarded the growth and fecundity of the worms used and also aVected the nutritional quality of vermicompost. The Wndings conWrmed the general hypothesis that growth patterns of composting species showed close relation with quality of the feed stock used as substrate. Acknowledgement One of the authors (Renuka Gupta) is thankful to University Grants Commission, New Delhi (India) for providing Wnancial assistance in the form of Junior Research Fellowship to conduct this work.

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