Vermicompost
Soil fauna including protozoa to mammals though not considered major is the important source of nutrients. Among the soil fauna earthworms have attracted more attention than others because of their importance in agriculture. Earthworm gut is the site of production of genuine humic acids which are distinct from the polysaccharide-gum humic acids. About half of the gums secreted by earthworm are in form of mucoproteins that help stabilizing pore space distribution. The earthworm soil casts are richer in available plant nutrients (nitrate nitrogen, exchangeable Ca, Mg, K and P) and organic matter. The earthworms through their casts and dead tissues supply about 60-90 kg N to the soil. Earthworm eats on fungal mycelia. Earthworms convert farm waste and organic residues into high quality compost. For this, Eisenia foetida, Perionyx exacavatus, Eudrillus euginiae and Lumbrius rubellus are important. These species can be cultured on organic wastes and dung. The technique of culturing them is called vermiculture and using these for decomposing residue to make compost is called vermicomposting.
About 1000 adult earthworms can convert 5 kg waste into compost per day. The earthworm assimilate 5-10% of the substrate and rest passes through the alimentary canal and is excreted as cast. Earthworm cast contains nutrients, vitamins, hormones and antibiotics. Vermi-compost is a stable fine granular organic matter, when added to clay soil loosens the soil and provides the passage for the entry of air. The multifarious effects of vermicompost influence the growth and yield of crops.Vermi
technology
Types
of earthworms in
vermicomposting
Earthworms
belong to phylum Annelida of Animal Kingdom. They are long and cylindrical in
shape and size having a large number of grooves. There are about 3000 species
of earthworms in the world which are adapted to a range of environment. More
than 300 species have been identified in India. Although, hermaphrodite, two
mature earthworms are required to propagate. At the time of egg laying, the
clitellum is transformed into hard, girdle like capsule called cocoon. Shedding
of cocoon ranges from 1 to 5, only a few of them survive and hatch. The
juveniles and again formation of cocoons takes a period of 50-60 days.
Normally, the average life span of earthworms varies with species ranging from
1 to 10 years.
Epigeics (surface feeders) are important in vermicomposting. The
epigeics such as Eisenia foetida and Eudrilus eugeniae are exotic worms and Perionyx excavatus is a native one being
used for vermicomposting in India. Epianecic are feeders on leaf litter and
soil at upper layers of soil. This group such as Lampito mauritii is indigenous and is active in in-situ
decomposition of organic wastes and residues in soil. Both epigeics and
epianecics groups of earthworms are slender, shorter in length and red to dark
brown in colour. They have high reproduction activity and efficient in
recycling of organic materials. Increased attention has been paid to Eisenia foetida and Eudrilus eugeniae which
have been found to be potential agent in vermicomposting of wide range of
agricultural wastes and can grow at a wide range of temperature varying from
0-40◦C and the optimum temperature ranges from 20-30◦C.
Mechanism
of vermicomposting
Materials consumed by worms undergo physical breakdown in the gizzard resulting
in particles < 2 µ, giving thereby an enhanced surface area for microbial
processing. This finally ground material is exposed to various enzymes such as
protease, lipase, amylase, cellulase and chitinase secreted into lumen by the
gut wall and associated microbes. These enzymes breakdown complex biomolecules
into simple compounds. Only 5-10% of the ingested material is absorbed into the
tissues of worms for their growth and rest is excreted as cast. Mucus
secretions of gut wall add to the structural stability of vermicompost.
Vermiculture
industry or vermicompost preparation: 1. Basic raw material: Any organic
material generated in the farm like bhusa, leaf fall etc., Horse dung, due to
the risk of Tetanus virus, lethal to human beings is not advisable to be used
as feeding material for earthworms. Paddy husk, marigold and pine needles have
also advised to be used as feeding materials for earthworms. 2. Starter: Cow dung, Biogas slurry, or urine of cattle
3. Soil animal: Earth worms (Species: Eisenia foetida) 4. Thatched
roof/vermished.
Favourable conditions of earth worms in the composting material:
A. pH: Range between 6.5 and 7.5
B. Moisture: 60-70% of the moisture below and above range mortality of worms taking place
C. Aeration: 50% aeration from the total pore space
D.
Temperature: Range between 180C to 350C
Procedure
Harvesting
of the vermicompost
Precautions
Do
not cover vermicompost beds/heaps with plastic sheets because it may trap heat
and gases.
Do
not overload the vermicompost heap to avoid high temperature that adversely
affect their population.
Dry
conditions kill the worms and waterlogging drive them away. Watering should be
done daily in summer and every third day in rainy and winter season.
Addition
of higher quantities of acid rich substances such as tomatoes and citrus wastes
should be avoided.
Make
a drainage channel around the heap to avoid stagnation of water particularly in
high rainfall areas in rainy season.
Organic
materials used for composting should be free from non-degradable materials such
as stones, glass pieces, plastics, ceramic tubes/bulbs etc.
Natural
enemies and their control
Transportation
of live worms
Conversion
rates:
1000 earth worms
may convert 5 kg waste material per day 1000 worms weighs about a kilogram
Rate of application of vermicompost