Pakistan is an agricultural country and but it has 1.95 percent population growth rate, which is higher than average growth rate of South Asian countries. At present it is the sixth most populous country in the world with projected population of 188 million. Pakistan with population of 363 million in 2050 is expected to retain the same position. The world population rate is increasing at high rate and by 2050; it is expected to be 9.9 billion. To feed this much population, increase in cropping intensity, excessive and intensive use of fertilizers has become the necessary evil. However, the chemical fertilizers are not environment friendly and causing water, soil and air pollution. Vermicomposting is an alternate option which is environmental friendly and safe product to increase the soil fertility. The annual cereal production will need to rise to about 3 billion ton (bt) from 2.1 but today and annual meat production will need to rise by over 200 million tons (mt) to reach 470 mt. To obtain the higher yields, there is need to use higher yield potential cultivars, upraising and maintaining the soil fertility level and soil conditions, efficient use of water, more protective ways to save crops from insects and pests. Among these factors, there is great need to increase and sustain the soil fertility. Plants use 50% of nitrogenous fertilizers applied to soil, 2-20% lost evaporation, 15-25% react organic compounds in the clay soil and the remaining 2-10% interfere surface and groundwater. However, in recent years, fertilizer consumption increased exponentially throughout the world, causing serious environmental threats. Fertilization may promote the accumulation of heavy metals in soil and plant system. Plants absorb the fertilizers through the soil and thus enter the food chain. This fertilization leads to water, soil and air pollution. The FAO estimates that food production needs to increase by 70% in 2050 to feed the global population (FAO, 2009). For example, in 1993-94, the offtake of fertilizer increased by almost 14%. In the following year in 1994-95, the yield per hectare of wheat increased from 1893 to 2081 kg/ha – an increase of almost 10%. Agriculture will need to develop substantially to feed future populations. Total fertilizer consumption has been growing steadily, from 31 mt in 1961 to 141 mt in 2002 (FAOSTAT, 2011). This situation calls for an increased search and research for alternate sources of nutrients to increase the soil fertility. More than 38 billion m3 of organic solid wastes (OSW) are produced annually from livestock, human, and crop activities worldwide. Three categories that represent a major part of OSW materials include bio-waste from households, waste water substrate, and the solids from biogas plant effluent (animal slurries).
Vermicompost
There is a great need to manage organic solid waste before the time they become severe. There are few options which can be adopted to overcome of this issue. One of them is vermicomposting. It is a biological method in which earthworms are used to decompose organic waste material such as straw, leaf, manures and other organic material into a very precious, useful and nutrient rich compound which is commonly known as vermicompost. It does not contain only micro and macro nutrients but also contain various types of useful microbes. These microbes take part in various biological processes which are essential for plant life.
Earthworm Types
There are about 1800 species of earthworm discovered. Which range from a few millimeters to one meter in length. There are three main types of earthworms.
(1) Compost worm
There are four species of compost worms. They live in the 12 cm of topsoil which is rich in decomposed organic material. They are usually found in manures and leaf piles. They burrow randomly through the topsoil and rotting matter. When the environment is too cold or hot they will burrow down and ball up. They cover themselves with slive to protect from drying and hibernate to conserve energy.
• Eisenia fetida (commonly known as Tiger worm or manure worm)
• Lumbricus rubellus (commonly known as Red worm or Blood worm)
• Eisenia andrei (commonly known as Red tiger worm)
• Dendrobaena venta (commonly known as Dendras or blue nose)
(2) Earth worker worm
This type of earthworm usually found in the garden. They till the soil by making it more airy and suitable for plant growth. They make long vertical burrows of up to a few feet deep, leaving their poo known as worm casts at their entrance. They feed on soil and partially on leaves. They come up to search for food at night and dawn.
(3) Root dwelling worm
This type of worm found in deep soils. These are found around the plant roots. Those worms could not be seen on topsoil. Example of this type worms
• Didymogaster sylvaticus
• Autrailan Megascolids australis
Material required for vermicomposting
A. Container
B. Bedding material
C. Organic waste material
D. Composting worm
A. The container doesnt need to be an expensive. Plastic tubs (with lid) are very inexpensive, light weight and retain moisture very well. Opaque bins should be used because worms are very sensitive to light.
B. Bedding material is a source of food for worms. It should be carbon rich and good absorbent. Manures, leaves, straws and shredded cardboard is a good bedding material.
C. Fruit waste, vegetable waste, tea bags, egg shell (best if crushed), well aged manures, grass clippings, plant waste and starchy material (like bread, rice and mashed potatoes) are great choice for vermicomposting. Human waste, pet waste, meat, dairy and oil foods are not recommended for vermicomposting.
Procedure
The desired material used in vermicomposting should be dried under the sunlight for 2 to 3 days. Make that material into small pieces so that earthworm may easily feed on it. Spread the bedding material, soil and the material which is to be vermicomposted in the container. Sprinkle the water and wet that material. Release the earthworm on this material (10 kg earthworm for 1 ton composting material). Keep the material wet otherwise the earthworm will not survive. The earthworms will start making soil granules after 2 to 3 days. These granules are called castings. These granules are collected and dried under shade.
Importance
1. Vermicompost transforms the organic solid waste into a stable and safer product which is used in sustainable agriculture.
2. It is ecologically responsible.
• It reduces waste in landfills and sewage treatment plants.
• It provides valuable additives to plants.
3. It saves money because the cost of artificial fertilizers is so high and have some negative impacts on the environment.
4. Vermicompost tea (a liquid) a new product extracted from vermicompost is used for diseases suppression.
5. It is also used as growth stimulator.
6. It controls the pathogens which causes the low yield.
7. It produces free and high quality soil amendments.
8. It is a source of income by selling earthworms for fishing and vermicompost as a source of nutrients.
Conclusion
Vermicomposting is a most precious, less expensive and environmental friendly method to handle the solid waste. In this method the organic matter is decomposed to such level that it can easily be stored, handled and applied to the crops. It has no negative impact on crops as well as on human being. This technology can be used for recycling of waste whose management otherwise difficult such as sewage sludge.
The writers are associated with the Department of Agronomy, University of Agriculture, Faisalabad, Pakistan.