BioCycle August 2008, Vol. 49, No. 8, p. 58
Utilizing vermicomposting improves soil fertility, reduces costs and mitigates pollution in the Philippines.
Rafael D. Guerrero III
THE Philippines has a robust agricultural economy with its extensive land and water resources. The production of crops such as rice, coconut and sugarcane, along with fisheries (aquaculture), is the mainstay of the country’s agricultural base.
One of the major constraints in the production of crops and fish in the Philippines is the high cost of inputs, particularly imported chemical fertilizers for crop production and feeds for aquaculture. Of environmental concern is widespread burning of crop residues such as rice straw and sugarcane trash. About 24 million tons of rice straw are generated annually. Livestock manure poses additional challenges. Approximately 28 million tons/year are generated, and improper discharge into water bodies is causing aquatic pollution and fish kills.
With the enactment of the Ecological Solid Waste Management Law, local government units have the primary responsibility of implementing the proper segregation, collection, storage, treatment and processing (composting, recycling, reuse, recovery, etc.) of waste streams appropriately, in accordance with ecologically sustainable development principles.
Various methods of composting municipal and farm solid wastes are used in the Philippines. One method that has become widely applied because of its simplicity, practicality and cost-effectiveness is vermicomposting. Resource-poor farmers can utilize vermicomposting to reduce the need for chemical fertilizers and pesticides, while recycling farm wastes to minimize environmental pollution. With less farm costs and less hazards to human health, the incomes and well-being of small farmers are enhanced.
Vermicomposting in the Philippines began in the l970s with studies conducted by researchers of the Central Luzon State University in Munoz, Nueva Ecija. The earthworms used in vermicomposting are “epigeic” (surface-dwelling) species, such as the “African nightcrawler” (Eudrilus eugeniae) or ANC. Tests have shown the efficiency of using vermicompost (VC) produced from agricultural wastes such as animal manures, rice straw, sugarcane trash, grass and leaves of leguminous trees (e.g., Gliricidia sepium).
Preparation and Process
To produce VC, the dried materials are first processed by shredding/grinding into small particles for more efficient degradation by microbes. The materials are preferably mixed to approximate a carbon to nitrogen ratio (C:N) ratio by weight of 25 to 35:l, which promotes optimum microbial activity. For instance, a mixture of 25 percent shredded rice straw and 75 percent rotted manure results in a substrate with a suitable carbon to nitrogen ratio of 30:l.
After adding sufficient water to the prepared materials for a moisture level of 70 to 80 percent, the mixture is placed in a closed container or covered with an impervious sheet (e.g., plastic) in beds for an anaerobic (thermophilic) decomposition period of 2 to 3 weeks. When the processed mixture in bins (indoors) or shaded outdoor beds is at an ambient temperature, it is ready to be stocked with the ANC.
The ANC is stocked at l kg per square meter of bin or bed (0.3 meter depth) with l50 kg of substrate and cultured for 4 to 6 weeks. With proper care and maintenance (having sufficient moisture, aeration and protection from predators), about 50 to 60 percent of the original weight of the materials is recovered as VC and a yield of 2 to 3 kg of earthworm biomass.
The VC at 40 percent moisture level is separated from the earthworms manually or mechanically using separators (e.g., trommels). For storage, fresh VC is air-dried for 2 to 3 days in the shade to a moisture level of 30 percent or less and kept in closed plastic bags. The quality of VC depends on the materials used and the methods applied.
Improved Crop Yields
While low in major plant nutrients (N-P-K) compared to chemical fertilizers, VC supports microorganisms (e.g., bacteria, fungi and yeasts), which make nutrients more readily available to plants and produce substances that promote plant growth and health. Aside from macronutrients, VC also contains essential micronutrients such as calcium, magnesium and iron.
Studies on the use of VC for crop production show that application of chemical fertilizers can be reduced up to l00 percent for certain vegetables and corn, and by 50 percent for rice and sugarcane. A field experiment in the Philippines using vermicompost with corn at 5 tons/ha increased ear lengths of plants by 114 percent, with the total yield comparable to that of plants fertilized at the recommended rate of inorganic fertilizer. For sugarcane, the use of 2 tons/ha of vermicompost, plus 50 percent of chemical fertilizer, increased the yield by 2.6 times compared to the usual yield using 100 percent chemical fertilizer.
In a recent pot experiment conducted in the Philippines on eggplant (Solanum melongena), results showed that a combination of VC at l00 g/pot (6.2 tons/ha) and 50 percent of the recommended chemical fertilizer application gave a significantly higher yield (l5 percent more) of eggplant fruits, compared to that with l00 percent chemical fertilization, after l20 days from planting.
Similarly, in another experiment with upland rice (Oryza sativa) in plastic containers, results indicated that use of VC at 0.5 kg per square meter (5 tons/ha) and 50 percent of the recommended chemical fertilizer gave a significantly higher yield (20 percent more) of rough rice, compared to that with l00 percent chemical fertilization, after l23 days from planting.
Earthworm biomass, a by-product of vermicomposting, can be processed into earthworm meal, or vermimeal, used as a valuable protein source for animal and fish feeds. On a dry weight basis, it contains 64 to 70 percent protein, 7 to 10 percent fat, 8 to 20 percent carbohydrate and 2 to 3 percent minerals. It is also rich in long-chain fatty acids and vitamins.
To promote the VC technology nationwide, a national vermicompost production program was launched in 2007, with support from the Philippine National Economic Development Authority and the Philippine Council for Aquatic and Marine Research Development. In partnership with local government units, state colleges and universities, and the private sector, the program runs technology demonstrations, trainings and technology transfers in regional centers throughout the country. To date, l6 regional vermicomposting production centers have been established in the country, which have trained more than l,000 farmers. Over 41 tons of VC and 1.5 tons of ANC have been produced for field trials on crop production and dispersal to farmers, respectively.
With the cost of producing VC at PhP 2 to 3 (US $0.04 to 0.07)/kg and market prices of PhP 5 to 8 (US $0.11 to 0.l7)/kg for VC in the country, vermicomposting is commercially viable. Farmers producing their own VC using available farm wastes can reduce their production costs for chemical fertilizers, which have skyrocketed in price, while minimizing environmental pollution and promoting soil/water conservation.
Dr. Rafael D. Guerrero III is executive director of the Philippine Council for Aquatic and Marine Research and Development. He can be contacted at: firstname.lastname@example.org.
August 20, 2008 | General
Vermicomposting Improves Farm Economics (Philippines)
BioCycle August 2008, Vol. 49, No. 8, p. 58