#702Vermicompost for vegetable gardens
702⸱AConcept
Benefits
- Improves soil structure and organic matter
- Improves soil life
- Improves plant nutrition
- Increases the yield
- Better nutrition of farmers and household members
Vermicompost is an earthworm-generated high-quality compost. It is a nutrient-rich biological fertilizer used in addition to or replacing mineral fertilizers. Its beneficial biological and nutritional properties enhance soil and plant health, accelerate their growth, and improve yields.
Vermicompost is produced in specially designed bins, pits, or beds. The organic base that serves as feedstock for composting worms consists of organic wastes such as greens, manures, coffee pulp and husks, and cardboard or straw. These materials are partly pre-composted, chopped or shredded, mixed, moistened, and layered. Then the composting worms are added. The worms chew, eat, mix, and aerate the waste. The mixture is kept moist, shaded, and at ambient temperature. After finishing the feed, the earthworms leave the mature compost and move towards new fodder.
Worm castings (vermicompost) and the protective mucus covering the worm skins are rich in nitrogen (N) in forms of proteins, plant-available ammonium, and urea, as well as phosphorous (P) and potassium (K), calcium (Ca) and Magnesium (Mg). They also contain enzymes, growth-stimulating hormones, and beneficial microorganisms. These properties feed and maintain both plants and soil life, creating a healthy growing environment. Vermicompost is a stable fertilizer which, contrary to synthetic fertilizers, is not easily washed out of the soil into the ground water.
After setting it up and having learnt how to manage it, the process is simple, efficient and cost-effective. In addition to obtaining the compost, excess worms can be used as animal feed (fish, poultry, pigs).
Vermiwash, the liquid leachate from vermicomposts, has similar beneficial properties and can equally be used as a liquid soil or leaf fertilizer to prevent disease and to promote healthy growth.
Vermicomposting can be carried out at different scales, depending on the intended purpose. This tool explains the production in small units, such as kitchen bins, buckets, or household composting containers. Here, the vermicompost is produced with domestic waste, such as fruit and vegetable peels. and applied in home gardens.
Medium-size or farm-level production units, such as worm beds with shade roofing, are intended to process larger volumes of organic material. For further information, please refer to Vermicompost.
702⸱BTo be considered
Vermicomposting can be an alternative or addition to hot composting (see Compost). Turning it is not necessary as the action of the worms aerates the materials. Vermicompost usually contains more total and plant-available nutrients compared to hot compost, and the microbial diversity is richer because the material does not heat up. Finally, it contains growth-enhancing enzymes and hormones which are not present in the hot compost.
On the downside, ambient temperatures mean that weed seeds are not destroyed by the worms. It is therefore critical to either avoid having seeds in the input material, or to use a combination of hot and vermicomposting methods for production.
Not just any earthworm species can be used for producing compost. Special composting worms must be purchased or sourced from nature and multiplied.
Earthworms don’t like light, heat, or drought. It is important to keep them in the dark and moist (not: wet!) and in medium to cool temperatures at all times. Also, they react sensitively to changes in aeration and composition of the feedstocks.
When the process is correctly managed, vermicomposting is an effective method for recycling organic wastes which would be problematic to add to the soil untreated (e.g. manures, coffee pulps or husks, kitchen or even human waste).
Timing
Start the process when it’s not too hot and enough water and green material are available, e.g. after the rainy season has begun.
If adding manures or wet organic wastes, they must be pre-composted two weeks before filling the bin/pit/container.
Composting worms can transform organic waste into humus in 1.5 to 6 months, depending on a variety of factors such as worm type and density, temperature, and moisure content, as well as quantity and preparation of organic wastes, and the overall management and attention to the process.
702⸱CImplementation
Through the composting process, the amount of the preparation reduces by 50-60 % in volume. That is why the inputs together have a larger volume than the final vermicompost. This needs to be considered when calculating the inputs for the required amount of vermicompost.
Materials
- Two plastic containers or bins with a lid. Must be stackable one above another, or use one container with a tray below. Dark color. Min. 25 liters volume, 50-75 cm height. Alternatively, any storage container made from wood, clay or other locally availably building material can be used.
- Drill. Hand or automatic. For drilling holes >0.7 cm.
- Fine insect screen. Without pesticide!
- Glue. To fix insect screen.
- Compost fleece. Optional.
- Compost worms. Purchased or collected when there is no commercial source available. Eisenia foetida (Red wiggler) and Lumbricus rubellus (Red worm), as well as Dendrobaena veneta are the most commonly used species for compost.
Examples for feedstock options:
Carbon-rich (structured) material: approximately 70-80%
- Coffee husks
- Rice husks/grain straw
- Shredded paper/cardboard. Avoid printed or coated paper!
- Sawdust
- Dry leaves
- Hay
- Coconut coir
- Mosses
Nitrogen-rich material: approximately 20-30 %
- Green waste, e.g. grass, weeds or bamboo
- Kitchen waste including eggshells
- Coffee pulp. Pre-dried or pre-composted for two weeks.
- Animal excrement. Pre-dried or pre-composted for two weeks.
- Tea dregs
- Pods of pulses or beans
- Coffee grounds
Amendments to the mixture
- Forest soil (5-10 %)
- Wood ash (max 10 %)
- Biochar (up to 8%, finely ground)
702⸱1Preparation
Earthworms that you find in normal soil may not be the type of earthworm that you need.
The screen must not be contaminated with pesticides/insecticides.
Exposing the heap or bucket with the earthworms to light can help to prevent the worms from escaping after collecting them. However, they always need sufficient soil and decaying material to hide.
702⸱2Procedure
Filling the container
If using cardboard, shred or tear it into 2.5 cm pieces or narrow strips.
The bedding should be about as moist as a wrung-out sponge.
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If adding eggshells, biochar and similar hard materials, make sure to crush them.
Bury moist materials to avoid fruit flies and odors.
Do not pack too tightly, use sufficient bulky materials as compactness could negatively affect aeration and temperature.
Avoid overfeeding the worms. The content of highly nitrogenous materials should be 20%, max. 30% of total. Too much nitrogen in the mixture will activate heat-producing microorganisms and turn the materials acidic and anaerobic. Worms don’t like heat and will try to escape or die. Preferably start with a high carbon content add more nitrogen-rich materials gradually later, while observing the worms’ behavior and vitality.
Mix highly carbon-rich materials, e.g. brown leaves, straw, shredded cardboard, (70-80%) and nitrogenous materials, e.g. weeds and food scraps (20-30%).
Moisture content should be about 70%. If you squeeze it and 2-5 drops come out, the humidity is adequate. If too dry, sprinkle with water.
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Monitoring and corrective actions
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Harvesting the compost
With a high worm population, kitchen wastes are decomposed in 4 to 6 weeks.
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Reproduction of composting worms
Both copulation partners produce a lemon-shaped cocoon of approx. 3.2 mm length. Two or more baby worms hatch in approximately 3 weeks. Baby worms are whitish to transparent and are 12 to 25 mm long. They will mature to breeding age in approximately 60-90 days.
Depending on the species and housing/feeding conditions, the population can double or triple in 2-3 months.
Excess of worms can be transferred to new composts or used for animal feed.
Worms can be bred in vermi-nurseries. Initial stocking densities between 2.5 kg/m² and 5 kg/m², as well as good monitoring and proper care for optimum conditions ensure highest reproduction rates.
Storage
Worm compost should be stored in a dry, shaded and well-ventilated place under a breathable fabric. It must be kept damp (not wet) to maintain microbial life. Compaction must be avoided to allow aeration.
It should sit for maturation for one month before application and ideally be applied within two months. If properly stored, the shelf life is 6-12 months before losing on its microbial quality.
702⸱DEconomic benefits
Lower fertilizer costs
This tool allows for a lower demand for synthetic fertilizers and therefore saves input costs over time.
Re-use of waste
The economic potential is particularly high if the waste products that serve as tool ingredients are produced on the farm or in the neighborhood, for example, manure from own cattle, straw or wood from the own field. Furthermore, by utilizing waste, this tool helps reduce landfill fees.
Additional income source
This tool has the potential to provide an additional income.
702⸱EGreen benefits
Less synthetic fertilizers needed
This tool reduces the need for synthetic fertilizers. This reduces carbon emissions and water pollution, improves soil life, and saves resources.
Better soil life
This tool helps improve soil life (microbes, earthworms, etc.). This plays a vital role in plant nutrition and contributes to a healthy ecosystem.
Re-use of waste
Reusing organic waste material in a circular economy saves resources from being discarded. This reduces the environmental load, carbon emissions, and water pollution.