**5. Effect of abiotic factors on vermicomposting**

The most important abiotic factors which affect vermicomposting process include moisture, pH, temperature, aeration, pH value, ammonia and salt content.


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*Vermicomposting: An Effective Option for Recycling Organic Wastes*

through the material for a period of time [60].

**6. Common methods of vermicompost harvesting**

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

The vermicompost is ready within 60–90 days and ultimately the material becomes black, granular, lightweight, moderately loose, crumbly and humus-rich. Watering must be avoided two to three days before emptying the beds to facilitate the separation of worms from the compost. Common procedures for harvesting the vermicompost are briefly described below. Any method may be adopted exclusively by preference. Moreover, two or more methods may be applied on the same pile.

This method is practiced if one wants to collect small amounts of vermicast just a few days after the compost pile is stocked with composting worms. In this case only top layer is covered with a thin layer of vermicast and rest of pile has not fully decomposed. The vermicast on top of the pile are simply gathered by hand/trowel and transferred directly into a container. This method is recommended if there is need of organic soil amendment in preparing a fertile potting mix. With time, as vermicompost is collected at the bottom of the pile it is further collected by hand.

The vermicompost is first gathered to form a pyramid like heap within the composting enclosure provided that the heap is exposed to light or it is transferred on to a flat surface elsewhere in open sun on a plastic sheet or a sack. This method of harvesting vermicompost takes the advantage of the earthworm's sensitivity towards light as they will tend to move deep into the pyramid. Vermicompost from the bottom, sides, and top surface of the heap is then collected by hand or with a trowel. After the first cycle of vermicompost collection, a few minutes are passed to provide sufficient time for the earthworms to move deeper and another cycle is commenced. For faster rate of harvesting vermicompost, the original heap is

This method of vermicompost harvesting is done manually with tool consists of mesh wire nailed on wood called sieve. A small portion from vermicompost pile spread on flat floor is transferred into a sieve and it is shaken so that fine vermicompost falls on the ground. Any undecomposed subtrates and earthworms are retained

This method of harvesting vermicompost is based on earthworms' ability to detect sources of food. Earthworms have the habit of abandoning the pile exhausted of food and moving towards fresher palatable source. Despite many modifications in this technique, but the basic principle is the same to provide fresh or more palatable food to cause the migration of earthworms from the exhausted pile to the new food source.

**6.4 Vermicompost harvesting by inducing the migration of earthworms**

Except for the first method, the rest are intended for bulk harvesting.

*DOI: http://dx.doi.org/10.5772/intechopen.91892*

**6.1 Manual harvesting of Vermicompost**

**6.2 Vermicompost harvesting by pyramidal heap**

divided into several smaller heaps.

**6.3 Screening or sieving of vermicompost**

in the screener and the worms are separated manually.

*Organic Agriculture*

lower than 10% [69].

around 15–30°C.

around 6.5–7.5.

hydrogen sulfide has accumulated.

content.

**5. Effect of abiotic factors on vermicomposting**

The most important abiotic factors which affect vermicomposting process include moisture, pH, temperature, aeration, pH value, ammonia and salt

1.**Moisture:** A strong relationship exists between the moisture content of organic wastes and the growth rate of earthworms. In a comparative study on vermicomposting process and earthworm's growth at different temperature and moisture ranges showed that 65–75% is most suitable range of moisture at all ranges of vermicomposting temperature [67]. The bedding used for vermicomposting must be able to hold sufficient moisture as earthworms respire through their skins and moisture content in the bedding of less than of 45% can be fatal to the worms. Although epigenic species, *E. fetida* and *E. andrei* can survive moisture ranges between 50% and 90%, but they grow more rapidly between 80% and 90% [20, 68]. The bacteria also plays vital role in vermicomposting. Its activity decreases in moisture content lower than 40% and it almost stops in

2.**Temperature:** Earthworm's activity, metabolism, growth, respiration and reproduction are greatly influenced by temperature [70]. The temperature for the stable development of earthworm population should not exceed 25°C [71]. Although *E. fetida* cocoons survive extended periods of deep freezing and remain viable [72] but they do not reproduce and do not consume sufficient food at single digit temperatures. It is generally considered necessary to keep the temperatures preferably 15°C for vermicomposting efficiency and 20°C for effective reproductive vermiculture operations. Temperatures above 35°C will cause the worms to leave the area or if they cannot leave, they will quickly die. Bacterial activity is also greatly depended on temperature as it multiplies by two per each 10°C increase in temperature and is quite active

3.**Aeration:** Earthworms are oxygen breathers and cannot survive in anaerobic conditions. They operate best when compost material is porous and well aerated. Earthworms also help themselves by aerating their bedding by their movement through it. *E. fetida* have been reported to migrate in high numbers from oxygen depleted water saturated substrate, or in which carbon dioxide or

4.**pH value:** The pH value is also one of the important factors affecting the vermicomposting process [73]. Epigenic worms can survive in a pH range of 5–9 [74]. The pH of worm beds tends to drop over time. If the food source/ bedding is alkaline, than pH of bed drop to neutral or slightly alkaline and if the food source is acidic than the pH of the beds can drop well below 7. The pH can be adjusted upwards by adding calcium carbonate or peat moss for adjusting pH downward can be introduced into the mix. Although microorganisms which are active in vermicomposting which can maintain their activity even in lower pH of around 4 but recommended pH range for compost is

5.**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% [75]. However, many types of manures

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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 [60].
