vermicomposting.pdf

Vermitechnology
The branch of science that deal with the importance
and utilization of different epigeic earthworm (live in area
with high organic matter) species to answer the
problems related to ecology and environment is known
as Vermitechnology.

Vermitechnology is useful technique for stabilization of both industrial
and domestic organic waste, organic farming and waste water
treatment.
Vermitechnology is an aerobic decomposition of organic wastes that
depends upon earthworms for fragmentation, mixture and promotion of
microbial activity.
During feeding, the earthworms fragment the waste materials that
results in increase of its surface area for further colonization of
microorganisms.

Charles Darwin was the pioneer of vermitechnology related studies.
He was the first man on this planet to demonstrate the role of
earthworms in the ecosystem. He published a book entitled “The
formation of humus through the action of earthworms” in the year
1881.
Since then, it has taken almost a century to appreciate its important -
contribution in curbing organic pollution and providing topsoil in
impoverished lands.
Since 1981, there has been increasing interest in possible methods
of processing organic wastes using earthworm to produce valuable
soil additives.
Since then both developing and developed nations have adapted

Vermicast or vermicompost, which is the final product of vermin-
composting, is richer in nutrients than the initial raw materials.
Vermicast appears as a peat-like material which is capable of showing
high water holding capacity, porosity, drainage, aeration and microbial
activity.
In vermicomposting, the essential plant macronutrients such as nitrogen
(N), phosphorus (P) and potassium (K) present in the organic waste
materials are converted through the action of microorganisms into much
more soluble and stabilized forms which are easily available to the plants as
compared to the parent substances.
Vermicomposting is best suited for mesophilic temperature range such as
35-40°C.

Selection of suitable earthworm species for vermicomposting is the
most important aspect of vermitechnology. Vermicompost produced by
different earthworm species exhibit significant variation in respect of
nutrient composition.
Perionyx excavates, Eisenia fetida, Eudrilus eugeniae and Metaphire
posthuma exhibit greater range of tolerance in extreme atmospheric
conditions than any other species of earthworms. So these are the most
widely used species of earthworms for vermicomposting of organic
waste materials. They can tolerate high temperature upto 42°C and low
soil temperature below 5°C.

It is assumed that earthworm excretes certain vitamins, metabolites and similar
substances into the soil which can be D vitamin or B vitamin.
The vermicompost those obtained from animal waste sources have more mineral
elements than the commercially available plant growth media.
The quality and quantity of nutrients present in vermicompost and its superiority
over traditional compost or synthetic plant growth media can be explained by higher
rate of humification (formation of humus. Humus is black amorphous substance produced
by the decomposition of dead and decaying organic matter by microorganisms),
breakdown of polysaccharides and accelerated mineralization of organic matter
resulting from earthworm activities during vermicomposting.

The peristomium is
the first true body
segment in an annelid
worm's body in the
anterior end. It is
directly behind the
prostomium and
contains the mouth,
tentacular cirri, and
sometimes feeding
palps, which may
instead occur on the
prostomium

VERMICOMPOSTING
Both physical and biochemical process are involved in the actions of the
earthworms.
Physical actions included are fragmentation, and aeration.
Biochemical actions involves enzymatic digestion, nitrogen enrichment,
transport of inorganic and organic materials.
During the biochemical process, important plant nutrients such as
phosphorous, potassium, nitrogen and calcium present in the waste materials are
converted through microbial action into such chemical forms which are much
more soluble and available to the plants than those in the parent substrate.

Earthworms not only are important for maintaining the role in plant nutrients
cycling, but also, they are equally responsible for maintenance of soil texture and
turnover of organic matter.
In agro-ecosystems, the most important effect of earthworms is the increase in
nutrient cycling, particularly nitrogen.
Overall, earthworms affect the physico-chemical properties of soil..
Vermicompost’s can also be defined as a sustainable biofertilizer generator from
organic wastes.

Physiology of Digestion
Earthworm feeds on dead and decaying organic matter present in the soil. This material
is gathered at night. The digestion of earthworm is an extracellular process.
The mouth and the buccal cavity takes part in the ingestion. There are many chemoreceptors present near
the mouth region which help in identifying chemicals and food they eat.
Food particles are drawn into the buccal cavity when the pharyngeal cavity is enlarged by the contraction
of muscles that extend from pharynx to the body wall.
The food is acted on by proteolytic enzymes present in pharynx which hydrolyse proteins and mucin helps
in the lubrication of food.
The food comes to gizzard passing through oesophagus. The gizzard works like a grinder. The food is
broken into minute particles by squeezing and rolling action.
The ground food enters the stomach where calciferous glands help in neutralizing the acid of the
food.

Then the food moves to the intestine, here amylase present in the intestinal caeca convert starch into
glucose.
Complete digestion of food takes place in the intestine. Various enzymes present in the intestine act on
food and digested food gets absorbed. Typhlosole increases the absorption surface of the intestine.
The undigested food passes to the rectum where water gets absorbed and the undigested food
is egested out through the anus in the form of castings.
The enzyme present in the intestine are:
Protease: Protein to amino acids
Amylase: Starch to glucose
Lipase: Fats to fatty acid and glycerol
Cellulase: Cellulose to glucose
Chitinase: hydrolyse glycosidic bonds in chitin

Success of vermicomposting process depends on a number of abiotic and biotic factors:
Abiotic Factors
Some of the very important abiotic factors which affect vermicomposting process include pH,
temperature, moisture content, aeration, feed quality, light, C:N ratio etc.
Moisture Content:
It is a necessary requirement for the working of earthworms and microorganisms in
vermicomposting system. Adequate amount of moisture is required. Since, earthworms breathe
through their skin; the system must have adequate moisture content. 60%-80% of moisture is
ideally required for vermicomposting.
Due to physical and chemical differences in feed stocks there may be slight variations. Even a 5%
difference in moisture content significantly affects the clitellum (The clitellum is a thickened
glandular and non-segmented section of the body wall near the head in earthworms and leeches,
that secretes a viscid sac in which eggs are stored) development in Eisenia fetida worm species.

pH
The acceptable pH range, suitable for earthworms and microorganism’s activity, is
5.5–8.5. Optimum pH is neutral or near neutral.
The pH value of feed substrates undergoes considerable changes during
vermicomposting. During vermicomposting of feed substrate, at the very initial stage, a
low pH is observed. The reason is that initially, during vermicomposting, there is
formation of carbon dioxide and volatile fatty acids.
Subsequently, with the evolution of CO2 and utilization of volatile fatty acids, the pH
begins to increase as the process progresses

Temperature
Earthworms grow at an optimum temperature range of 12-28 degree C. With the
increase in temperature, there is a significant effect in the activity of earthworms.
It is generally recommended that temperature should be maintained above 10 degree
C in winter and it should be maintained below 35 degree C in summer. Decrease in
temperature results in reduced metabolic activity of earthworms and also, they are
not able to reproduce.
At very low temperatures, earthworms do not consume food. At higher temperature
(above 35 degree C) metabolic activity and reproduction of earthworms begins to
decline and mortality occurs. Variations in preferences for temperature as well as in
tolerance vary from species to species.

Aeration
Since, they are aerobic, oxygen is essential for vermicomposting. Earthworms
consume oxygen, which is a function for their microbial, oxygen levels are also
related to substrate temperatures.
Continuous supply of moisture will result in poor aeration during
vermicomposting system and can also affect the oxygen supply to worms.
Ammonia and salt content:
Earthworms cannot survive in organic wastes containing high levels of
ammonia. Worms are also very sensitive to salts and they prefer salt contents
less than 0.5%. However, many types of manures have high salt contents and if
they are to be used as bedding, they should be leached first to reduce the salt
content, it is done by simply running water through the material for a period of
time.

Feed Quality
One of the major requirements for vermicomposting process of earthworm is
suitable feed material. Variations are observed in the amount of food which can be
consumed by earthworms. It is so because of a number of factors such as the state
of decomposition of food, C: N ratio of food, food particle size, salt content in
food, etc. Minimum particle size of feed waste ensures the worms to accelerate the
process of vermicomposting. Due to small particle size of feed waste, aeration is
provided properly through the pile of waste material which is later on available to
worms. A worm generally consumes food of about 100 to 300 mg/g body
weight/day. Nutrition is provided to earthworms from living microorganisms,
organic materials, and by decomposing macro-fauna.

Light
Since earthworms are photophobic in nature, they should be kept away
from light.
C: N Ratio
Growth as well as reproduction of earthworms is also affected to some
extent by the C: N ratio of feed material. Higher C:N ratio in the feed
material accelerates the growth and reproduction of worms. Waste
degradation is slowed due to too high or too low C:N ratio. Plants cannot
assimilate mineral nitrogen unless the C: N is in the range of 25–20:1.

BIOTIC FACTORS
A number of biotic factors also affect the vermicomposting process which
includes microorganisms, enzymes earthworms stocking density, etc.
A number of activities such as reproduction rate, feeding rate, respiration rate,
and burrowing activity affect the earthworm population, i.e. stocking density
during vermicomposting.
Mortality rate increases in higher population densities. One earthworm
produces reduced amount of cocoon. Also, growth rate is decreased. Marked
reduction in rate of growth as well as reproduction in E. andrei has also been
observed due to increase in stocking density.
A rapid turnover of fresh organic matter into earthworm casts was also seen
due to high population densities of earthworms

Microorganisms
•The microbes present in the vermicomposting process plays a very important role
in waste composition of those particular components. Stabilization of organic
matter due to mutualistic interaction is seen between earthworms and
microorganisms during vermicomposting.
•Earthworms consume fungi with organic substrates to fulfil their protein or
nitrogen requirement, fungal population in earthworm casts was almost equal or
higher than that of initial substrates.
•The micro-organisms not only mineralize complex substances into plant available
form, but they also synthesise biologically active substances

Enzymes
•Complete stabilization requires enzymatic action for chemically organic wastes are
very complex. The worms stimulate enzymes in their gizzard and intestine. A quick
biochemical conversion, as a result, a rapid biochemical conversion of proteinaceous
and cellulosic materials takes place.
•Most common enzymes required in vermicomposting are cellulases, amidohydrolase,
proteases, urease, b-glucosidases, and phosphatases. Enzyme activities have often been
used as indicators of microbial activity and can also be useful to interpret the intensity
of microbial metabolism in soil.
•Being a catalyst of a number of metabolic functions, they also decompose and
detoxify a number of contaminants

Status of Earthworms
•All over the world, there are about 3,320 species of earthworms.
•It has already mentioned that with about 590 species of earthworms, found in
different ecological preferences, the functional role of a number of the species
and their influence on the habitat are lacking.

Habitat of Earthworms
Species of earthworms have different ecological niches, life style habitat
characteristics, and life span. The dispersal of earthworms is related to the
physico-chemical characteristics of soils.
Prominent among these are pH, carbon, nitrogen temperature, moisture, and C:N
ratio etc. Majority of earthworm species prefer soil with a moisture of 12–34%,
temperature of 10–35 0 C, pH of about 7 and C:N ratio 2–8. Earthworms are
generally absent or rare in soil with a very rough texture in soil and high clay
content, or soil with pH

Eisenia Fetida
The most prevalent earthworm for vermicomposting is Eisenia fetida. Most
popularly it is also known as red wriggler, red worm, tiger worm etc. The
species has been widely used for various toxicological studies as test worm.
Upto 1500 mg body weight can be acquired by mature earthworms. An adult
worm on maturation produces one cocoon every third day. On hatching from
each cocoon within almost 23 days 1-3 individuals emerges.

General properties of vermicompost
In terms of sustainable crop production, the acceptability of vermicompost has
been rising rapidly as soon as the human realizes the significance of organic inputs
in crop field. The excreta of earthworms, which is considered as the main product,
that is, vermicompost has several characteristics. These are:
Physical properties
A good vermicompost is always non-toxic, well-decomposed, ecologically
compatible, and environment friendly.
Any type of green waste viz. municipal waste, agricultural waste, sewage sludge,
industrial waste, and human feces can be used for the conversion by earthworm.
When turning of soil is occurred in proper manner, it is symptomatic to aerobic
decomposition which will produce normal odor after preparation. If there is
improper aeration, foul odor can be formed.
The final outcome of vermicomposting would be comprising of fine particulate
structure, granular form.
Vermicompost plays the role of a “soil conditioner” by improving the soil porosity,
drainage, and water holding capacity.

Properties Compost Vermicompost
pH 7.16 7.72
EC (dSm−1) 3.65 6.88
OC 20.5 17.3
Total N (%) 2.42 3.5
Total P (%) 0.88 0.71
Total K (mg.kg−1) 653.5 950.5
Total Ca (%) 2.9 3.5
Total Mg (%) 1.5 2.8
Total Fe (mg.kg−1) 4467 6045
Total Zn (mg.kg−1) 115.5 189.5
Total Cu (mg.kg−1) 59 38
Total Mn (mg.kg−1) 221.45 344.15
C:N 8.47 5.51

Chemical properties
Vermicompost is rich in almost all essential macro and micro plant nutrients. Several
experiment states that average nutrient content of vermicompost is greater than other
conventional compost, produced from other procedures.
Among all the secondary nutrients, calcium content in vermicompost is higher than
other compost.
In contrast with other conventional compost, vermicompost contains worm mucus
which facilitates in preventing washing away of nutrients present there [20].
Due to vermi-conversion, heavy metal present in feeding material is found to be
reduced in earthworm cast owing to its accumulation in worm tissue. According to the
feed used, the rate of removal of heavy metal depends in vermicomposting techniques.
This property makes vermicompost lesser contaminant than any other compost. Thus, it
becomes more environmentally sustainable [21].
There are certain differences found in chemical properties between simple farm yard
compost and vermicompost. Vermicompost ranges higher in macro and micro-nutrients
as well as soil organic carbon status that can be observed from the Table.

Biological properties
The by-product of earth casting is an inhabitant of several microorganism,
viz. bacteria, fungi, and actinomycetes. These micro-organisms release
several enzyme and phytohormones which helps in improving plant growth.
Thus, vermicompost facilitates both microbial and enzymatic activity [22, 23].
The microbial population of nitrogen fixer bacteria and other symbiotic
associative bacteria are supposed to be in a good range of numbers in the
excreta of earthworm.
In addition, earthworm casts harbor a large number of vesicular-arbuscular
mycorrhiza (VAM) propagules. These propagules survive up to 11 months on
the cast, and helps in increasing microbial activity to produce nitrogen and
phosphorus in readily available form to the plant.

Properties Impact
Soil physical properties
Soil aggregation, soil structure, and water holding capacity,
infiltration rate improves after vermicompost application.
Soil chemical properties
Vermicompost also offers a greater chance for reducing salinity,
alkalinity, and reduction of heavy metal contamination.
Soil microbial properties Microbial biomass is also increases with the use of vermicompost.

Beneficial effects of vermicompost
Effect of vermicompost on the soil physiochemical properties
Addition of vermicompost improves soil physico-chemical properties viz. soil
structure, soil water holding capacity, penetration resistance, bulk density, soil
organic carbon, aggregation, nutrient content, etc. According to the findings
of various long term research addition of vermicompost reduces the bulk
density of the soil and increases the water holding capacity of soil [25].
Aksakal et al. [26] found that when vermicompost was added in the soil, the
mean bulk density, and mean total porosity were the least. Air permeability
rose and penetration resistance reduced dramatically as wet aggregate
stability improved and bulk density reduced. Increased microbial population
and activity led in the development of aggregates and increased soil porosity,
resulting in decreased particle and bulk densities. Physicochemical
characteristics such as pH, electrical conductivity (EC), porosity, moisture
content, water holding capacity, and chemical properties like nitrogen,
phosphorous, potassium, calcium, and magnesium were all found to be
significantly improved in vermicompost treated soil, while the corresponding
physicochemical values in control soil were minimal in rice crop [27].

Vermicompost has indeed been found to have significant concentration of total and bioavailable nitrogen,
phosphorus, potassium (NPK), and micronutrients, as well as microbial and enzyme activity and growth
regulators [28]. Polysaccharides appeared to be abundant in vermicompost [29]. Polysaccharide worked as
a cementing ingredient in the soil, causing aggregate stability, which helped to establish and maintain the
soil structure for improved aeration, water retention, drainage, and aerobic conditions. The preservation of
soil structure is essential for root elongation and nutrient uptake. The inclusion of mucus secretion and
microorganisms from the earthworm’s gut improves the soil’s aggregate stability. The absorbent organic
matter in vermicomposts increases the soil’s water retention capacity by holding only the quantity of water
required by the plant roots [30]. Vermicomposts have been found to have a higher base exchange capacity
and a higher oxidation potential rise [31]. The C/N ratio of vermicompost is usually lower, indicating that it is
more suited for use as a soil amendment. By altering the physiochemical parameters of the soil,
vermicompost was able to limit the loss of nutrients through leaching [32]. Humic acid and biologically active
compounds like plant growth regulators are abundant in vermicompost [33]. Humic acid has been proven to
improve nutrient accretion in situations where nutrients are scarce or when additional nutrients are provided.
Humic acids may have a hormone-like effect on plant growth and productivity as a result of their involvement
in cell respiration, photosynthesis, oxidative phosphorylation, biogenesis, and a variety of other enzymatic
functions.

Effect of vermicompost on the soil biological properties
Biological properties of soil can be enhanced through application of
vermicompost. Recent studies founded that soil biological characteristics viz. soil
organic carbon as well as soil microbial biomass, enzymatic activity, population of
different beneficial microorganism, hormones, etc. significantly enhanced with
application of vermicompost [34]. The activity of the dehydrogenase enzyme,
which is commonly employed to quantify the respiratory activity of microbial
communities, was shown to be higher in vermicompost than in commercial
medium [35]. Application of vermicompost improved the nitrogen status of soil by
introducing the beneficial microorganism in the rhizosphere of the plant which
ultimately enhances the nitrogenase activity in soil, which is the enzyme
responsible for nitrogen fixation

Effect of vermicompost on the soil fertility
Vermicompost has a great importance to increase the soil fertility level. In recent
years organic amendments are getting more importance for nutrient
management and sustainable crop production since the long-term use of
inorganic fertilizer lacking organic additives has the ability to ruin soil qualities
[34]. Long-term treatment of balanced inorganic fertilizers led to reduced soil bulk
density, improved total porosity, and higher water-holding capacity. Inorganic
fertilizers also promoted soil aggregation in deeper soil layers and raised maize
and wheat grain and straw yields [38]. In their research, using farmyard manure
(organic fertilizer) instead of inorganic fertilizer improved soil qualities in a similar
way. Furthermore, compost provides substantially higher boosts in soil organic
carbon as well as some plant nutrients when compared to mineral fertilizers
[39, 40]. Thus, using vermicompost improves overall soil fertility by improving
numerous soil physical, chemical, and biological qualities.

Effect of vermicompost on plant growth and development
Vermicompost promotes the growth and development of a variety of plant
species, especially various horticulture crops, that is, sweet corn, tomato,
strawberry [41], cereals crop rice [27], wheat, sorghum [32], fruit crops
papaya [42], and pineapple [43]. Several growth and yield metrics viz.
stem diameter, plant height, marketable yield per plant, mean leaf
number, and total plant biomass of tomato plant were recorded
significantly higher with the application of vermicompost. The increase in
growth and development of plant is due to the improving action of
vermicompost application on soil physical, chemical, and biological
properties which ultimately improves the overall soil fertility, which
enhances the plant growth and development. Vermicompost has been
demonstrated to improve plant dry weight [44] and uptake of plant N [45]
serve as a naturally available, slow released sources of plant nutrients

Effect of vermicompost on bioremediation and detoxification of
industrial wastes
Vermicompost has a greater importance in bioremediation and
detoxification of industrial waste. Because of their robust metabolic system
and the participation of earthworm gut bacteria and chloragocyte cells,
earthworms have the potential to valorize and detoxification of heavy
metals in industrial by-products. The majority of research found that
vermicompost made from organic waste comprises greater concentrations
of humic chemicals, which are important for plant growth [49]. Earthworm
has a vast role in bioconversion of waste materials. Because of their robust
metabolic system and participation of varied intestinal micro biota,
enzymes, and chloragocyte cells that decrease hazardous forms to benign
forms, earthworms have the ability to bio-convert and detoxify most heavy
metals in industrial sludges

Effects of vermicompost on soil organic matter Earthworm casts ingested soils often have
much higher content of soil organic carbon and nutrients availability as compared to
surrounding soils (Lee, 1985). The studies undertaken by Maheswarappa, (1999) revealed
that vermicompost addition in soil enhanced organic carbon status, decreased bulk density,
improved soil porosities and water holding capacities, increased microbial populations and
dehydrogenase activity in the soils. It has been documented that organic matter content in
worm casts was about four times more than in surface soil with average values of 48.2 and
11.9 g kg-1 soil, respectively (Khang, 1994). Moreover, earthworms contribution to N
turnover in cultivated soils ranged from 3 to 60 kg ha-1 year-1 (Crossley, 1988; Bostom,
1988), thereby enhancing N availability to plants (Tiwari et al., 1989; Hullugalle and Ezumah,
1991).

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