VERMITECHNOLOGY AND ORGANIC FARMING
Venniteclmology is a method of converting all the biodegradable wastes into usefi.il product, i.e., vennicompost, through the action of earthworms. Vennicompost is a sustainable bio-fertilizer regenerated from organic wastes using earthworm, which contains 1.2 to 6.1% more nitrogen, 1.8 to 2.0% more phosphate, and 0.5 to 0.75% more potassium compared to farmyard manure. It also contains hormones like auxins and cytokinins, enzymes, vitamins, and useful microorganisms like bacteria, actinomy- cetes, protozoans, and fungi (Ansari and Ismail, 2001). This process of decomposition results in the production of vennicompost. Vennicom- post or castings is wonn manure. It is considered by many in the fanning arena to be the very good soil improver. The nutrient content of castings is dependent on the material fed to the worms, and woims are commonly fed materials with high nutrient content (Ismail, 1997). It is the wonn castings that provide these nutrients in a foim that is readily available to plants. The biology of the wonn's gut facilitates the growth of fungus and bacteria that are beneficial to plant growth.
Vennicomposting is a simple biotechnological process of composting, in which epigeic species of earthworms are used to enhance the process of waste conversion and produce a better end product. Vennicompost is a nutrient-rich organic soil conditioner that can be applied to improve soil conditions for a wide range of soil types. The use of earthworms is very essential in this process, as the worms act for the composing of organic matter into a stable nontoxic material with good structure, which has a potentially high economic value and also acts as a soil conditioner for plant growth. Vennicomposting has many environmental benefits is proven to be an easy way of getting rid of garbage waste. This technique is also beneficial to the soil and results in a lower use of synthetic fertilizers.
Vennicomposting units can be set up in many ways. This system can be set up in a large box, a bucket, a bin, a basket, and even in a pit in the soil. It is very important to keep in mind that a vennicomposting unit should be more than 1 meters in depth, but maybe as long as prefened in width. It is also veiy important to note that such a unit is set up in the shade. Organic matter that is added to the unit should be diy to prevent an increase of temperature in the unit. The unit should be kept moist; therefore, watering is very essential. The amount of materials which are layered during the building of the unit depends on the size of the unit, which is set up. The basic layering in a vennicomposting bin is as given in Figure 12.1.
FIGURE 12.1 Layering in the vennicomposting unit.
The basal layer of the venni-bed comprises of broken bricks followed by a layer of coarse sand (10 cm thick) in-order to ensure proper drainage. A layer (10 cm) of loamy soil should be placed at the top. 100 locally collected earthwonns were introduced into the soil. Fresh cattle dung is scattered over the soil, and then it was covered with a 10 cm layer of dried grasses. Water is sprinkled on the unit in order to keep it moist. The dried grasses, along with cattle dung, is turned once a week. After 60 days, vennicompost units are regularized for the harvesting of vennicompost eveiy 45 days. When the layering is completed, the unit should be covered with dried leaves and left for 60 days. During the period of these 60 days, organic material and cow dung should be added on a weekly basis, while watering every other day, depending on the moisture content of the material in the bin.
Vennicompost should be ready for harvesting in a maximum of 40-45 days. When the organic material in the unit is changed completely in structure and smells soil-like, it is ready for harvest (Figure 12.2). The compost should be pressed in hand to check on moisture content. Before harvesting, no water should be added to the unit for 3-4 days, and a heap of the compost should be formed after harvesting. These actions will derive the earthworms in the deeper layers of the unit, where the moisture content is slightly higher. On the fourth day, the compost can be harvested and is ready to be used for agricultural purposes. This compost can be used directly in the soil and can be stored for 3 months if disposed of well in a plastic bag.
FIGURE 12.2 Vennicompost at harvest.
BENEFITS OF VERMICOMPOST
Vennicompost not only benefits soil, but also impact soil economics. It improves the physical structure, enriches the soil with microorganisms. Microbial activity in worm castings is 10 to 20 times higher than in the soil and organic matter that the wonn ingests thereby attract deep-bunowing earthworms already present in the soil to enhance burrowing activity. It also improves water holding capacity. Vermicompost plays a major role in improving the growth and yield of different field crops, vegetables, flowers, and fruit crops and enhances germination, plant growth, and crop yield. It Improves root growth and structure (rhizosphere) and enriches the soil with microorganisms (adding plant hormones such as auxins and gibberellic acid). It is a good quality organic soil additive that enhances the water holding capacity and nutrient supplying capacity of the soil and also brings about the development of resistance in plants to pests and diseases, thereby providing a sustainable environment in the soil. A waste recycling through vermicomposting causes no pollution, as it becomes valuable raw materials for enhancing the soil health. It helps to close the "metabolic gap" through recycling waste onsite and thereby cause a reduction in greenhouse gas emissions such as methane and nitric oxide (NO) (produced in landfills or incinerators when not composted or through methane harvest).
Venniwash is one of the materials produced by vermicomposting, which is an "ecobiotechnological process that transforms energy-rich and complex organic substances into a stabilized vennicomposts" primarily through the action of earthworms but with support of other microorganisms. Vemiwash contains the soluble nutrients that were released in the vermicomposting process (Nath et al., 2009). Organic fertilizers such as venniwash provide a relatively cost-effective and safe alternative to chemical fertilizers. According to Ansari and Sukhraj (2010), the use of chemical fertilizers, which is widespread in many developing countries, can lead to soil damage and reduced soil health and production levels while increasing the incidence of pests and disease and environmental pollution. Venniwash is a liquid that is obtained when water is left to flow slowly through a vennicomposting-like unit. Venniwash has fertilizing abilities and has also proven to have a pesticidal action when applied as a foliar spray. The layering of a venniwash bin is the same as a vermicomposting unit, with the exception that this unit consists of a bucket to which a tap is attached at the lowest point to collect the venniwash when ready. The organic matter that is added to this unit varies from ordinary grass clippings to plant material with pesticidal properties. The organic matter should be dried for 3 to 4 days to accelerate the composting action and regulate the temperature in the bin.
The vermiwash unit is set up using buckets (Figure 12.3). A tap is fixed on the lower side of each bucket. The bucket is placed on a stand to facilitate the collection of vermiwash. About 5 cm of broken pebbles are placed at the bottom of the buckets followed by 5 cm layer of coarse sand. Water is then allowed to flow through these layers to enable the settling of the basic filter unit. A 15 cm layer of loamy soil is placed on top of the filter bed. Approximately 300 earthworms are introduced into the soil. Dried grass and cattle dung are placed on top of the soil. The vermiwash unit is left to regularize after 60 days for the collection of vermiwash eveiy day. Approximately 0.5 liters can be collected on a daily basis. After layering the different material to the bin, the unit is left for 60 days to regulate with the tap open. Organic matter and cattle dung should be added on a weekly basis as needed. The unit should be watered eveiy other day depending on the moisture content in the bin. Access water should be left to flow through the open tap. Vermiwash will be ready to collect when the liquid that is flowing through the tap gets pale yellow in color. When the color change is seen, the tap should be closed, and water should be allowed to drip through the unit overnight. The following day the tap should be opened, and the vermiwash should be collected in a plastic container. The color intensity of the vermiwash will differ according to the organic material that is added to the bin. After the first collection, vermiwash can be collected on a daily basis by repeating the same process of adding water to the unit. The venni- wash that is collected can be kept stored for 3 months in plastic containers. Vermiwash can be used by a dilution of 10% of the vermiwash with water and spray to the desired plant/crop.