EARTHWORMS AND THEIR ROLE IN SOIL FERTILITY ENHANCEMENT
Dr. Ashok Kumar Panigrahi
Earthworms, the night crawlers in the organic matter rich soils have long been recognized as friends of farmers the world over; belong to the section of animals called, invertebrate. Taxonomically they come under the phylum Annelida, class Oligochaeta, and order Opisthophora. This order consists of five large families of earthworms world wide such as; Moniligastridae, Megascolidae, Eudrilidae, Glossoscolecidae and Lumbricidae. The economic importance of all the worms of the world has been studied in details. It is found that more or less most worms play significant role in enhancing soil fertility and from amongst these a countable few contribute the most. Researchers have identified and named more than 4400 distinct species of earthworms, each with unique physical, biological and behavioral characteristics that distinguish each one of them from the other.
Classification of Earthworm
Earthworms are variously classified; often on the trophic lines and also on the habitat lines. The trophic classification divides the earthworms in to three categories; phyto phagous, phyto-geophagous and geophagous when the habitat classification also divides them in to three; epigeic, anecic and endogeic categories. When their economic importance is considered both these systems of classifications are found overlapping. For example, the epigeics are phytophagous. Epigeic earthworm species, represented by Perionyx excavatus (oriental), Eisenia foetida (European) and Eudrilus euginiae (African) live on the soil and feed on the decaying plant and animal parts. Epigeic worms build no permanent burrows, preferring the loose topsoil layer rich in organic matter, specifically leaf litter, to the deeper mineral soil environment. Even in nature these worms are found in highest concentrations in the naturally occurring drifts of leaves and organic debris rather than in soil We can replicate the preferred environment of these worm species in bin culture, and it is largely for this reason that it is the epigeic worms only which are used in vermicomposting and vermiculture systems world wide. These are phytophagous and humus formers.
Similarly, anecics are phyto-geophagous. Anecic species, represented by the common night crawlers Lampito mauritii (oriental) and Lumbricus terrestris, live in the top six inches of the soil and feed on those organic matters which have become parts of the top soil. Anecic worms build permanent vertical burrows that extend through the upper top and mineral soil layer, which can be as deep as 4-6 feet. These species coat their burrows with mucous that hardens to prevent collapse of the burrow, providing them a home to which they will always return and are able to reliably identify, even when surrounded by other worm burrows. When deprived of this burrow environment anecic worms will neither breed nor grow. Anecic worms feed on soil bound decaying organic matters and are responsible for cycling huge volumes of organic soil incorporated surface debris into humus, nearly the same as the epigeics. Lastly, the endogeics are geophagous. This category, represented by worms like Metaphire posthuma, Pheretima elongata Octochaetona serrata and O. thurstoni, (Indian) are large worms, often reaching a meter or more in length. These worms live deep in the soil feeding exclusively on the mineral soil which incidentally is also rich in organic matters. Endogeic species, deep burrowers, build extensive, largely horizontal burrow systems through all layers of the upper mineral soil. These worms come to the surface only during the rainy season just to deposit their voluminous castings, spending their lives deep in the soil where they feed on decayed organic matter and mineral soil particles. While most people believe all worms eat soil, it is only the endogeic species which actually feed on soil. These worm species help incorporation of mineral matters into the topsoil layer besides aerating the productive top soil through their movements and feeding habits. Thus, all the three trophic categories of earthworms play significant roles in soil fertility management.
Earthworms and soil fertility
All the worms named above are important as far as soil fertility is concerned each playing same or different roles. Their contributions come in the forms of their faecal matters, called ‘worm cast’, besides their body secretions or extrusions which they secrete and excrete as they are both exonephric and enteronephric. The gut of the earthworms act as ‘bioreactors’, where under ideal conditions of temperature, moisture and pH, desired strains of aerobic bacteria get multiplied and undesired strains of anaerobic bacteria get digested. The gross contribution of earthworms to soil fertility is, in fact, the bacterial and fungal biomass which they excrete that enhances soil fertility. That is the reason why it is said that what the nature takes about hundred years to achieve; the earthworms accomplish the same in just one year. Earthworm concentration in a soil is an indicator of beneficial bacterial-fungal biomass presence and that soil does not need much care as far as soil fertility is concerned.
Earthworms are voracious feeders. According to one estimate of daily food consumption per thousand kilograms of body weight, an elephant consumes about four kilograms, a man consumes about twenty kilograms, a mouse consumes about two hundred kilograms, an earthworm consumes about five hundred kilograms, the fungi, two thousand kilograms and a bacterium, twenty thousand kilograms. It makes the bacteria, the ‘super consumers’ in the animal kingdom. Decomposition of organic matters in the open facilitates the breeding or multiplication of bacterial populations of both aerobic and anaerobic types. Anaerobic bacteria carry out incomplete combustion of organic matters and release only five percent of energy. They also produce incompletely oxidized molecules like methane and other obnoxious compounds, thus polluting the atmosphere. They make no direct contribution to soil fertility. Ingested by earthworms, the anaerobics when get digested in the gut of the worms, the aerobics get multiplied, The nitrogen fixing nitrifying bacteria, such as Azotobactor, Azospirillum, and phosphate solublising phosphosolube bacteria (PSB).are all aerobics.
Although the total numbers of microorganisms in earthworm gut contents and casts depend on the initial food source, the greater the organic matter content the larger the microbial population. In all cases there is an increase in microbial population and activity during
passage through the gut. Parle (1963) showed that numbers of bacteria and actinomycetes increased 1000 fold during passage through the gut and oxygen consumption remained higher in earthworm casts than in soil for 50 days, indicating an increased microbial activity. This enhanced microbial activity is probably responsible for the increased phosphatase and urease activity found in earthworm casts (particularly of L. rubellus and A. caliginosa), compared to underlying soil. However, it is probable that the interaction of earthworms and the soil micro flora is more complex than mere mixing of microorganisms with finely-ground organic material. An early study by Lunt and Jacobson (1944) showed that casts from a ploughed soil in Connecticut, U.S.A., had approximately three times the concentration of exchangeable Mg, seven times of available P and eleven times of available K than the top 150 mm of soil. Recent studies (Sharpley A N and Syers J K; 1977) on the chemical nature of P in surface casts collected from a pasture soil in New Zealand have indicated that surface casts contain approximately four times more loosely-bound inorganic P and twice as much loosely-bound organic P as underlying soil. A greater isotopic exchangeability of inorganic P in casts was associated with the more extensive release of inorganic P from casts. The amount of loosely bound inorganic P extracted from freshly-deposited casts increased as a function of time of incubation, while the release of organic P showed the converse trend, consistent with the changes in phosphatase activity. Similar differences in the amounts of extractable NH4-N (amoniacal nitrogen) and NO3-N (nitrate nitrogen) between surface casts and underlying soil have also been obtained, (Syers J K, Sharpley A N and Keeney D R; 1979).
Institutional worm culture for worm cast harvest in India
A number of institutions in India are engaged in worm culture for harvesting worm casts. To name a few, the names of such institutions come to fore such as New College, Chennai, Navdanya Trust, Dehradun, INORA, Pune and Bhawalkar Earthworm Research Institute (BERI), Pune. BERI, Pune is doing it on a commercial basis, exporting worm casts abroad where it fetches good money. These institutes, however, culture different species of earthworms for harvesting worm casts. BERI for example has selected Pheretima elongata, New College, Lampito mauritii and Octochaetona serrata, Navdanya, Eisenia foetida and INORA, three species of epigeic-phytophagous worms such as Eisenia foetida, Eudrilus euginae and native Perionyx excavatus. The author is in agreement with INORA for the sake of biodiversity, although knows that only Eisenia foetida is the best as far as large scale and commercial worm cast harvest is concerned. Potentially, all these three species are more or less on the same parameter but Eisenia being more docile among them, is more suitable for culture. Admittedly, Eudrilus, being larger in size can produce more casts than Eisenia in the same time period. Soil fertility wise casts of Eisenia are more potent than others. The author, hence, recommends Eisenia foetida (60%), Eudrilus euginiae (30%) and native Perionyx excavatus (10%) in cultures for vermicomposting.
Factors influencing the culture of Earthworms
In the practice of worm cultures, the following factors need be taken care of to avoid future complications leading to failure of the same leading to possible financial loss.
1. Oxygen requirements
Earthworms are oxygen-breathing animals and absorb oxygen directly through their skin. Oxygen is dissolved into the mucous coating on the worm’s skin and then passes through the skin and the walls of blood capillaries lacing the skin to blood where it is picked up by hemoglobin and carried throughout the body.
2. Moisture requirements
Moisture is critical to the survival of earthworms as any other animal; but in earthworms, it provides the ability to absorb oxygen. To facilitate the absorption of oxygen, the skin is very thin and permeable, meaning that the moisture within the body cavity can easily be evaporated off, particularly in dry environments. The moisture range for most worm species is from 60-85%, which ensures the worm to absorb as much moisture from the surrounding as may be lost through evaporation. Hence, earthworms need a more moist environment than most other animals.
3. Temperature requirements
Specific temperature requirements and tolerances vary from species to species, though the ideal range for most epigeic worm species is roughly between 60-800 F. The worm’s ability to tolerate temperatures outside of ideal, is highly dependant on the level of moisture in the system; with hot and dry conditions being the most lethal combination for the worms.
4. Nutritional requirements
Earthworms lack teeth in mouth and sufficient digestive enzymes in the gut. They rely instead on microorganisms in the organic matter to rot and soften it so that it can be ingested, then relying on naturally occurring bacteria and fungi in their gut to digest the food. In the process of taking in this biologically active predigested organic matter, the earthworm also ingests small particles of sand and soil, which get lodged in their highly muscular gizzard. As the organic matter with the microbial mass coating it move through this gizzard, they are ground against the gritty particles lodged there and get fragmented into smaller pieces, making them easier for the gut organisms to complete digestion and absorption of nutrients present in it!
Researchers, however, now understand that it is not from the organic matter itself, but from the bodies of the microbial life rotting the organic matter that the epigeic earthworms derive the bulk of their most vital nutrients. Once thought to be detritus (debris) feeders, we now understand that the earthworms are actually predators of microbial life, relying on microscopic bacteria, fungi, protozoa and algae as their major sources of nutrition. Thus, anything that will support microbial activity, that is, anything that rots, is potentially suitable as food for the earthworms. Materials that support the greatest level of earthworm activity are those that support the greatest and most diverse populations of microbial life.
5. pH requirements
As microorganisms break down complex organic matter, it goes through a series of naturally occurring changes in pH. Because earthworms thrive in environments rich in decaying organic matter they are adapted to tolerate these pH fluctuations with little or no change in their body activity levels. In nature, worms are found in environments with a pH range from 4-9, with physiological and reproductive rates being no different at an acidic 4 than they are at an alkaline 9. In fact, all things being otherwise equal, earthworms actually prefer an environment with a pH of 5 to 5.5, contrary to the popular belief that they prefer a neutral pH. With a pH tolerance this wide, it is highly improbable for pH to be a limiting factor in any worm system. Further, the radical and artificial adjustment of the pH through the addition of buffering agents like lime can actually have a detrimental effect on the worms. The organisms present in a given environment of organic debris are there because they are suited to that environment together with whatever fluctuation may naturally occur through the process of decay. When the nature of the system is suddenly and radically altered, it forces many of these organisms into dormancy and sometimes kills them outright, thus reducing the availability of nutrition to the worms and potentially slowing the processing rate of the organic matter leading to a slower rate of growth and reproduction.
The addition of lime to any worm system is generally discouraged except in those extremely rare circumstances where the pH has dropped well below the worms’ level of tolerance.
6. Response to light
All earthworms are photophobic to some degree, meaning they react negatively to bright light. The severity of the reaction depends on the species of worm, how bright the light and the level of light to which the worm is accustomed. For example, earthworms accustomed to some light exposure will react less negatively to sudden bright light than will worms accustomed to complete darkness. Some species of worms react negatively to bright light but are actually attracted by dim light. Earthworms sense light through photoreceptors lodged on their dorsal surfaces and on the prostomium (sensitive lobe of tissue overhanging the mouth that the worm uses to probe and sense its environment).
Earthworms are hermaphrodites, meaning each worm possesses both male and female reproductive organs. Some earthworm species are self fertile, meaning they fertilize their own ova to produce young, and some species are parthenogenetic, meaning that the ova can grow to young without fertilization. However, such instances are very rare. Most earthworm species require two worms exchange sperms between them in order to produce young. When worms mate they lay side by side with their heads pointed in opposite directions, making close contact along the upper segments of their bodies. They secrete a mucous coat that binds them together, preventing them from being easily pulled apart and ensuring environmental conditions like rain or dew do not interfere with their exchange of sperm. The exchanged sperms are stored in the spermathecae located in the anterior segments ahead of the clitellum. Once they exchange sperms, a process that may take hours, the worms move apart and eject their own ova through the female pore on their skin surface in to the clitellum. They secrete a thick mass of mucous around the clitellum, which hardens on the outside but remains sticky underneath, forming a band out of which the worm backs off, drawing the band over its head. As the band carrying the eggs passes over the spermthecae, the sperms are squeezed out and mix with the ova. Once the worm has completely backed out of the hardened mucous band, the ends close forming a ‘cocoon’ with sperm and ova inside and then fertilization takes place. Each worm will continue to produce cocoons until they have used all of the sperms they received from their mates. The length of time it takes for the juveniles inside the cocoon to mature and hatch out, and the number of juveniles per cocoon depends on the worm species and prevailing environment.
Worms are a closed species, meaning they can produce viable young only with the sperm from members of their own species. They cannot be hybridized. In those rare circumstances when two worms from differing species have attempted to mate, the result was either no young being produced or, in rare circumstances, juveniles produced were sterile. The author has observed in a mixed culture of Eisenia with Perionyx, there were a few hybrids.
The cocoon is an incredibly tough structure, designed to protect the young inside from environmental extremes and even ingestion by other animals. Cocoons can be frozen, submerged in water for extended periods of time, dried and exposed to temperatures far in excess of what can be tolerated by adult worms without damage to the young worms inside. The cocoon can even be eaten by other animals, provided it can make it past the teeth, surviving the digestive process and passing out of the animals’ body in the faeces. In areas of climatic extremes it is likely that the adult members of epigeic worm species do not survive, but the cocoons do, repopulating the environment when normal environmental conditions return to a range that can support worm activity.
Earthworm cocoons are easy to spot in the worm bed. They are roughly the size of a large grape seed and similarly shaped, with one end rounded and the other drawn out to a point. When first dropped from the body of the parent the cocoon is a creamy, pearlescent yellow, darkening to a cola brown as the young worms within mature and prepare to emerge.
Earthworm species used in vermiculture
Earthworm taxonomists have identified thousands of individual worm species, yet only five/six of them have been identified as useful in vermicomposting systems to date. These species were evaluated on the basis of their ability to tolerate a wide range of fluctuating environmental conditions, handling and disruption to the worm bed, and for their growth and breeding rate. Earthworm species with a relatively short life span, rapid growth and reproductive rate, have been identified as most effective mainly because there occur the high concentration of juvenile worms present in their populations. Juvenile worms, like human teenagers, are voracious consumers, keeping the processing rate of the system high and ensuring an ongoing succession of young worms.
The growth and reproductive rates of each worm species listed below are the maximum under ideal conditions. These rates, however, may decline with the changes in the environmental conditions within the system that shift away from the ideal. The nature and character of these important vermicomposting worms are discussed below
1. Eisenia foetida/Eisenia andreii (common name: Red Worm)
The two worm species are listed together because in virtually all cultures of E. foetida, E. andreii is present. E. andreii so closely resembles E. foetida in behavior, environmental requirements, reproductive and growth rate, and appearance that the only way to distinguish between the two is through protein analysis. There are no apparent physical differences between the two species. For all intents and purposes these worms can be considered identical. Eisenia foetida is generally the only worm mentioned because the two are so closely associated and because E.foetida is typically the more populous of the two.
Eisenia foetida/Eisenia andreii are the worm species identified as the most useful in vermicomposting systems and the easiest to grow in high-density culture because they tolerate the widest range of environmental conditions and fluctuations, and handling and disruption to their environment of all species identified for this purpose. E. foetida/E. andreii are also common to almost every landmass on earth, meaning there is essentially no concern over importing potentially alien species to an environment where they might cause damage. This worm species is considered the premier worm for most applications, is a comparatively small worm, not always suited for use as bait, hence, spared for cultures. The culture criteria and known qualities of this species are as follows:
Temperature range: Minimum; 380 F, maximum; 880 F, ideal range; 700 F to 800 F.
Reproductive rate: Approximately 10 young per worm per week under ideal conditions.
Average number of young per cocoon: Approximately 3 (on an average).
Time to emergence from the cocoon: Approximately 30-75 days under ideal conditions.
Time to sexual maturity: Approximately 85-150 days under ideal conditions.
Food of choice/ preferred food: fresh cow dung.
2. Eudrilus euginae (common name: African night crawler)
This worm is a very temperamental worm to raise in cultures and has the tendency to crawl out for no particular reason. It is often used exclusively in the casting production market. The marketing of this worm for bait or for land reclamation has been very limited. It produces typical cast that is no better than any other castings except for looks. This worm is often marketed as ‘red worm’ to the unsuspecting bait dealer. It is very easy to hold these worms between temperatures 70 and 80 degrees F to promote capsule production. They are however, very prolific feeders and breeders.
This worm is a semi-tropical species, meaning it cannot easily tolerate cool temperatures and is usually grown indoors or under temperature controlled conditions in most areas of North America. E. eugeniae is well suited for use as a bait worm, but does not tolerate handling or disruption to its environment. E.euginiae is a large worm (adults reach 14 cm long) that grows rapidly, taking as little as 5 weeks to reach maturity, and is extremely prolific (Dominguez et al., 2001). Its feeding habits (surface feeder, deposits its casts on the surface) make it ill suited for certain vermin-composting systems, such as the raised gantry-fed beds (Borges et al., 2003). E.euginiae has a narrower optimal temperature range, between 20 – 29ºC (Neuhauser et al., 1988), than other vermicomposting earthworms, and as such is better suited for tropical than temperate applications. Individuals have been known to perish above30ºC (Loehr et al., 1985; Viljoen and Reinecke, 1992; Dominguez et al., 2001). In addition, this species is more sensitive to disturbance than Eisenia foetida and may occasionally migrate from breeding beds (Dominguez et al., 2001). Despite these disadvantages E.euginiae is capable of rapidly converting a wide range of organic matters in to vermicompost in a comparatively shorter period of time. Eudrilus eugeniae completes its lifecycle in about 65-80 days. Although earthworms are bisexual, their mode of reproduction is through cross-fertilization. Adult worms take 15-21 days after the copulation to lay the cocoons (approx. 400 cocoons in 2 months). Again 15-21 days are taken to hatch the eggs present inside the cocoon into neonates. Neonates attain adulthood in 35-60 days.
This species is used in some vermicomposting systems around the Mediterranean region and in some areas of Asia including India. The specific qualities of this species are;
Temperature range: Minimum; 450 F, maximum; 900 F, ideal range; 700 F to 800F.
Reproductive rate: Approximately 7 young per worm per week under ideal conditions.
Average number of young per cocoon: Approximately 2 (on an average)..
Time to emergence from the cocoon: Approximately 15-30 days under ideal conditions.
Time to sexual maturity: Approximately 30-95 days under ideal conditions.
Food of choice: partially decomposed cow dung and precomposted water hyacinth.
3. Perionyx excavatus (common name, Indian Blue worm or simply, India Blue)
This worm is known for its mass migrations at the on set of rains and has been found on top of buildings during rain storms. Some authors seem to think that it is the presence of a toxin produced by anaerobic bacteria that trigger this mass migration at early rains. This worm is a prolific breeder and consumes large amounts of organic waste. The author uses a combination of this species with Eudrilus euginiae and the red worm (Eisenia foetida) in vermicomposting mixed organic wastes. The red worms and Eudrilus will consume feed that is ‘cow dung’ below the surface as well as feed on the surface. Whereas the Perionyx is strictly a top feeder feeding exclusively on leaf litter and if one covers the old feed with new feed, they will not consume the old feed. In mixed cultures, the contribution to casting production by the red worms will be around 60% to 70% .The easiest way to identify them is to compare the location of the clitellum. In Perionyx the clitellum is much closer to the front end when in Eisenia, it is away from the anterior end. Besides, the colour of Perionyx is darker cherry when the same of Eisenia is light flesh or red, hence, the name. Eudrilus is a larger worm having a body colouration intermediate to the other two.
Perionyx excavatus is a beautiful worm with an iridescent blue or violet sheen to its cherry dark coloured skin clearly visible under bright light. It is a thin long and fast moving worm that reacts violently when touched. It is poorly suited as fishing bait, but has an impressive growth and reproductive rate far in excess of the other species grown in bin culture.
This is another tropical worm species with a very poor tolerance for low temperature fluctuations in the bin environment, handling or disruption to the system. P. excavatus is often referred to as the ‘Traveler’ for its tendency to leave the bin en masse during rain.
Due to its temperamental nature this species is rarely used in vermicomposting systems in monoculture conditions, but this tendency is substantially reduced in mixed cultures with Eisenia foetida and even Eudrilus euginiae. The culture criteria of this species are:
Temperature range: Minimum; 450 F, maximum; 900F, ideal range; 700 F to 800F Reproductive rate: Approximately 19 young per worm per week under ideal conditions.
Average number of young per cocoon: Approximately 1.
Time to emergence from the cocoon: Approximately 15-21 days under ideal conditions.
Time to sexual maturity: Approximately 30-55 days under ideal conditions.
Food of choice/ preferred food: partially decomposed leaf litter
Other worms of the world in cultures:
4. Amynthas gracilus (common name, Alabama or Georgia jumper)
A. gracilus is another large worm species well suited for use as bait. It is also a tropical species with a poor tolerance for cold temperatures. This worm tolerates handling and disruption to the worm bed as well as does E. foetida and is generally considered an easy worm to culture provided appropriate temperatures can be maintained.
A. gracilus is used in a few vermicomposting systems in Malaysia and the Philippines. Temperature range: Minimum; 450F, maximum; 900F, ideal range; 700F 800 F.
Reproductive rate: Undetermined, though believed to be similar to E. eugeniae.
Average number of young per cocoon, time of emergence from the cocoon and time of sexual maturity: Undetermined, though believed to be similar to E. eugeniae.
5. Eisenia hortensis (European night crawler)
E. hortensis is a large worm species well suited for use as a bait worm. Its ideal temperature range is a bit cooler than is that of E. foetida and it requires higher moisture levels than do the other species tested for use in bin culture and vermicomposting, but the species tolerates handling and disruption to its environment, and environmental fluctuations very well. Because this worm has a very low reproductive and growth rate, relatively speaking, it is considered the least desirable species of those tested for either bin culture or vermicomposting systems. It is used in a few vermiprocessing systems in Europe for the remediation of very wet organic materials.
Temperature range: Minimum; 450 F, maximum; 850 F, ideal range; 550F – 650F.
Reproductive rate: Just under 2 young per worm per week under ideal conditions.
Average number of young per cocoon: Approximately 1.
Time to emergence from the cocoon: Approximately 40-125 days under ideal conditions.
Time to sexual maturity: Approximately 55-85 days under ideal conditions.
Vermicomposting is defined as the practice of using concentrations of earthworms to convert organic materials into usable vermicompost or worm castings. These systems focus on the organic waste material and managing it so that it can be successfully and efficiently processed in a worm system.
Castings production systems are worm-processing beds that use feed stocks specially blended so that castings have a specific nutrient value, chemical characteristic or cross section of microorganisms. The focus of these systems is on end product value.
Vermiculture systems focus on producing the maximum level of worm biomass possible in a given space. Worm systems are typically managed for one of the three reasons; such as – waste management, production of worm biomass, and production of castings. While worms are being grown, organic materials are being processed, and castings are being generated in all worm beds, management methods may vary depending on the focus of the system.
An experiment with water hyacinth as vermibed material for Eudrilus euginiae:
Six-month long trials were conducted in several vermibeds each with one of the following forms of water hyacinth; (a) fresh whole plants, (b) dried whole plants, (c) chopped pieces of fresh plants, (d) ‘spent’ weed taken after extracting volatile fatty acids (VFAs), (e) precomposted fresh weed and (f) precomposted spent weed. The first four forms were studied with and without cow dung. The experiments revealed four clear trends as under; (i) the precomposted forms were the most favoured ones as feed by Eudrilus eugeniae, while the fresh whole form was the least favoured, (ii) different forms of spent weed were favoured over the corresponding forms of fresh weed, (iii) blending of cow dung (@20% of the feed mass) with different forms of water hyacinth had a significant positive impact on worm cast output, growth in worm zoo mass, and production of offspring relative to the corresponding unblended feed, and (iv) in all vermibeds, the ‘parent’ earthworms steadily grew in size over the six-month span, and produced offspring. There was no mortality. The experiments thus confirmed that water hyacinth can be sustainably and even commercially vermicomposted with Eudrilus eugeniae.
This experiment also proves beyond doubt that the abundantly available aquatic weed, water hyacinth, Eichhornia crassipes could be commercially processed to generate high quality vermicompost in large quantities. The weed was first composted by ‘heap’ method and then subjected to vermicomposting in vermibeds operating at steadily larger densities of earthworm than recommended hitherto; 50, 62.5, 75, 87.5, 100, 112.5, 125, 137.5, and 150 adults of Eudrilus eugeniae per kilogram of vermibed volume. The composting step was accomplished in 20 days and the composted weed was found to be vermicomposted three times as rapidly as uncomposted water hyacinth [Bioresource Technology 76 (2001)]. The studies substantiated the feasibility of heap composting–vermicomposting systems, as all vermibeds yielded consistent worm cast output during seven months of operation. There was no earthworm mortality during the first four months in spite of the high animal densities in the reactors. In the subsequent three months a total of 79 worms died out of 1650, representing less than 1.6% mortality per month. The results also indicated that an increase in the surface-to-volume ratio of the reactors might further improve their efficiency.
Suggested methods of vermicomposting:
There are three, shed covered indoor methods of vermicomposting. They are as under: 1.Wind row method, 2. Pit/tank method and 3. Heap method.
The first and foremost requirement in vermicomposting is production of large quantities of desired worms for worm inoculation. A ‘breeder box’ has to be used for this purpose. A
breeder box, used for getting the worms multiplied in large numbers for inoculation may be either a wooden box or a paper cartoon with polythene cover inside or a crate or an earthen pot. A crate of the size, 60cm X 60cm X 5cm can hold a population of adult worms numbering 3000- 4000 of E. foetida, 1500–2000 of E. eugeniae and 1000+ of P. excavatus.
Take15 kg of mixture of fresh cow dung (50%) and hay pieces (50%) in a box with a polythene sheet inside/ a large earthen pot (different for different species) and keep it indoor. Keep the mixture wet by sprinkling water over it. After two days, release 50 numbers of earthworms in to the box. Within two months, the earthworms may multiply 300 times producing 600 to 1000 juveniles. The same can also be done in a ‘vermiwash’ unit, prepared essentially to get vermiwash. Large numbers of worms are required for inoculation in vermibeds. Surplus worms can also be sold in the market commercially.
1. Wind row method:
All biodegradable wastes including cow dung and hay are decomposed in the open in the heap method and are then laid on vermibeds in wind rows on the pucca floor of the shed which has a breadth of 12 feet and length, as per the space available/budget. 2 vermibeds each of 3 feet wide are first laid on the sides with the middle space of 3 feet being left vacant. The height of the vermibeds should not be more than one foot. 10-12mm thick fresh cow dung paste is laid on the vermibeds and is left for some time till the extra water is seeped in. The mass is then pierced profusely by sticks up to the bottom and left as such for one day or till the walls of the holes are hard enough not to collapse when sticks are removed. Diversity based epigeic worms of the species, E. foetida (60%), E. euginiae (30%) and P. excavatus (10%) are released from the breeder box at the rate of 1 kg. per every 10 feet length of each vermibed. The moisture content of the beds is maintained by sprinkling water as per actual necessity. After about a fortnight, the beds are covered with gunny bags to help retain moisture and to ward off worm predators. However, there must be a water channel always full of water around the shed to keep the red ants at bay. After about 2 months or when the masses become rich in worm cast, watering of the same is discontinued and a fresh row in the vacant middle portion is laid and watered. Worms from the old nearly dry masses will migrate in to the freshly laid mass. Then the side rows can be harvested and stored in poly jute bags without further drying for future use. Fresh vermibeds can be laid on the sides when the middle bed is ready for harvest. This method is the best for large scale harvest of vermicompost as well as worms for commercial purpose.
2. Pit/Tank Method:
Biodegradable waste materials are filled into indoor shallow pit/tanks, not deeper than two/three feet, followed by sparse spray of water just necessary to moisten the waste mass. The surface is then sealed with 50mm thick layer of cow dung paste, and at every 300mm distance, holes of 50mm diameter are made and sticks are kept inserted into them for two continuous days and are later removed. This provides the track for air circulation. The well-aerated material does not emit any foul smell. After two weeks mixed epigeic earthworms of the species such as Eisenia foetida, Eudrilus euginiae and Perionyx excavatus in the ratio of 60:30:10 are released on the surface. They enter into the organic matter through the holes on the surface. The set-up is left without disturbance for six weeks. Water is sprinkled occasionally on the surface during the composting process. The cow dung pack is not required to be separated as the same is eaten by earthworms from below the surface and the resulted casts are deposited on the surface. The casts along with the multiplied population of earthworms is harvested. The entire set up may be covered by old jute (gunny) bags which act as cover of the containers. These bags themselves, however, will get composted after some time.
Frequent harvesting of Eudrilus eugeniae is necessary to reduce their population pressure and enable continuous growth of the earthworm population.
3. Heap method:
In this method, composting is done on the floor indoor. Biodegradable organic material is piled up on the floor preferable a permanent surface/ pucca floor of the shed.
Step 1. The platform should have a water channel around it to prevent red ants from coming in. Use a polythene sheet to cover the ground of the area in lieu of pucca floor.
Step 2. Place the cow dung/FYM and other organic material in layers as below.
First layer — Spread a layer (10 cms) of heap decomposed plant material;
Second layer – Sprinkle fresh cow urine on top of the decomposed plant material;
Third layer — Spread a layer (15 cms) of decomposed cow dung/ FYM/ biogas slurry
Fourth layer —Release earthworms, 1000-2000 in number or @ 5 kg per ton of biomass;
Fifth layer — Spread a layer (10 cms) of decomposed cow dung/ FYM/ biogas slurry;
Sixth layer — Spread a layer (10 cms) of dry crop residue/ green succulent leafy material
plus fresh cow dung;
Seventh layer — Spread a thick layer of mulch with cereal straw on the top. It prevents loss
of moisture and acts as a barrier to predators like birds.
The heap should form a dome/ pyramid shape finally.
Sprinkle water over the whole mass at 3-day intervals for 2 months, to maintain adequate moisture and body temperature of the worms.
In about 60 days, worm casts are deposited on the surfaces and vermicompost is ready for harvesting. The well formed material is black in colour, quite light in weight and has a pleasant, earthy smell.
Maintain the heap till the entire mass is full of worm casts; then separate the worms manually and release them in to a freshly laid heap.
Alternative to the 4th.–7th.layers, Cow dung/biogas slurry may be pasted over the 3rd. layer and the biomass is allowed to decompose for 20 days. After 20 days earthworms are released on the heap that enters inside through the cracks developed on the surface in the mean time. This method is the cheapest of all the methods described here.
Rate of vermicompost applications in different agricultural crops:
Recommended application rate= 1-1.25 t/Ac. or 3-4 t/ha.
Suggested method of vermicompost applications:
Vermicompost to be applied around the base of the crop plants after removing top soil, in vegetable crop, flowering plants and fruiting trees in the following rates.
Fruit Trees: 5-10 kg/ tree; Vegetable crops: 3-4 t/ ha; Flowering plants: 500-750 kg/ ha.
(fractions of the cultivated land may accordingly be calculated)
Note: 1. There is no danger of over application of vermicompost as in the case of the
agrochemicals, except that it is not required.
2. The fruits and vegetables produced using vermicompost do have a far better taste
and all of them do have a comparatively longer keeping quality.
NPK analysis of ‘worm casts’ collected from agro ‘ecosystem soil’ measured in terms of kilogram per hectare under standard methods.
General soil sample parameters
Worm cast of Metaphire posthuma
(Giant tropical earth worms of Orissa that can not be cultured in captivity)
Initial soil sample parameters
Worm casts of mixed species worms
-do- Perionyx excavatus
-do- Eisenia foetida
-do- Eudrilus euginiae
NPK analysis of ‘worm casts’ collected from ‘vermibeds’ of two different sources
- 1.43 %
- 0.54 %
- 1.4 %
Yield data of farmers practicing organic farming and growing vegetables commercially (using vermicomposts with standard application rate, 1-1.25 ton per acre)
Tomato – Rabi
Brinjal – Rabi
Ribbed gourd – Kharif (Rain)
Brinjal – Rabi
Chili – Rabi
Brinjal – Rabi
Chili – Rabi
Brinjal – Rabi
Chili – Rabi
Tomato – Rabi
Note: From field experiences, it has been found that application of vermicompost with worms has a far better result than application of only vermicompost.
Yield data of farmers practicing Chemical farming and growing vegetables commercially
Brinjal – Rabi
HYV Tomato (Jyoti)
HYV Tomato (Century)
Data source: Navdanya-Orissa, Balasore, Orissa (Annual Report, 2008-09.)