Vermiculture
Vermiculture is the culture of earthworms. The goal of vermiculture
is to continually increase the number of worms in order to obtain a
sustainable harvest. Vermicomposting is the process of converting
organic material into a humus-like material known as vermicompost.
Production of vermicompost requires maximum worm population density
all the time. However, to produce more worms, the population density
should be low enough that reproduction rates are optimised. The worm
Eisenia fetida commonly known
as 'compost worm', 'manure worm', 'red worm' or 'red wiggler' is
extremely tough and adaptable can be found wherever piles of manure
have been left to age for a few months. The
compost worm has a capacity for very rapid reproduction.
Advantages
- Vermicompost is superior to conventionally produced compost
- Worms can be used on farms as high quality animal feed
- Vermicomposting and vermiculture are potential sources of supplemental income to farmers
Disadvantages
- Rapid production of vermicompost requires more labour
- It requires more surface area as worms being surface feeders do not operate in material more than one meter deep
- Vermicomposting is more vulnerable to environmental pressures like freezing and drought
- Start-up resources in the form of initial investment, time and labour are required
Compost worms need:
- A conducive environment to thrive called 'bedding'
- Food
- Adequate moisture (>50% water by weight)
- Adequate aeration
- Protection from temperature extremes
'Bedding' provides worms with a
stable habitat. It should have the following essential
characteristics:
- High absorbency
- Good bulking potential
- High Carbon:Nitrogen (C:N) ratio
The bedding material may be made-up
of 'peat moss', 'horse manure', 'Newspaper' or 'paper mill sludge'.
Selection of bedding material is very important to successful
vermiculture. Manures are the most commonly used feed stock. The
bedding must hold sufficient moisture for the earthworms to thrive.
Worms cannot survive in anaerobic conditions. Earthworms
thrive in temperatures in the range of 20s(C). Such temperature
ranges stimulate reproduction. However, they die in temperatures
exceeding 35(C). Compost worms will redistribute themselves according
to temperature gradient.
Worms
can survive in the pH range of 5 to 9. Worms
are very sensitive to salts, preferring salt contents less than 0.5%.
Few toxic components to earthworms are:
- De-worming medicine in manure
- Detergent cleansers, industrial chemicals and pesticides
- Tannins
Earthworms in ideal conditions
reproduce quickly. Worm populations double every 60 to 90 days. Ideal
conditions being:
- Adequate food
- Well aerated bedding with moisture content between 70 and 90%
- Maintaining temperature between 15 to 30 C
- Initial stocking densities more than 2.5 kg/m2 but less than 5 kg/m2
Stocking density refers to the
initial weight of worm biomass per unit area of bedding. Starting
with a population density less than stocking density will delay the
onset of rapid reproduction. Population
density of worms greater than stocking density results in low
reproduction as there is greater competition
for food and space. The most
common densities for vermicomposting are between 5 and 10 kg/m2. Worm
growers tend to stock at 5 kg/m2 and tend to split beds when the
density has doubled. Following these guidelines, growers can expect
doubling of biomass in 60 days. Theoretically a stock of 10 kg of
worms can become 640 kg in after one year and 40 tonnes after two
years. The barriers in
achieving optimum rates of reproduction are:
- lack of knowledge and experience
- lack of dedicated resources
- lack of preparation for winter
Rule of thumb is that one
ton of input results in one cubic yard of compost.
The
most common pests and diseases that earthworms are at a risk of are:
- Moles
- Birds
- Centipedes
- Ants
- Mites
- protein poisoning
The three basic types of
vermicomposting systems are:
- windrows
- beds or bins
- flow-through reactors
- Vermiculture focuses on production of worms rather than vermicompost.
- Vermicompost can be used as a method for destroying pathogens.
- Vermicompost spread on land does not cause contamination of ground or surface water.
- Vermicompost binds nutrients well thereby preventing nutrient run-off from agricultural land and ultimately preventing eutrophication of surface waters.
- There is potential for using compost worms in natural filtration systems.
- One of the principal benefits of vermicomposting is 'carbon sequestration'.
- Vermicomposting also addresses the issue of worldwide depletion of carbon in soils. By consistent application of compost or vermicompost an increased level of carbon in soil has been seen.
- Worms aerate the matter as they move through it resulting in fewer anaerobic areas and reduced methane emission.
- One unit of vermicompost is as effective as five to seven times of fertilizer in promoting plant growth and yield. Vermicompost is more efficient at retaining nitrogen.
- Earthworms have a very important role in counteracting 'the loss of biodiversity'.
- Vermicompost has a high potential value monetarily.
- Vermicomposting and vermiculture are environmentally beneficial processes that have great potential as components of sustainable agriculture.
