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worm casting facts

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   Facts on worm castings





Vermicomposting uses earthworms to turn organic wastes into very high quality compost. This is probably the best way of composting kitchen wastes. Adding small amounts of wet kitchen scraps to a large compost pile in the garden day by day can disrupt the decomposition process so that the compost is never really done. But it works just fine with vermicomposting.

Many gardeners use vermicomposting systems for all their garden and kitchen wastes, many more use both types of composting, and thousands of households without gardens use neat and unobtrusive worm boxes indoors to compost their kitchen scraps (as well as newspapers and cardboard boxes), reducing their garbage by up to a third and providing their own organic soil for pot plants and container gardens on balconies and roofs to grow their own healthy food.

See "Friend Earthworm: Practical Application of a Lifetime Study of Habits of the Most Important Animal in the World" by George Sheffield Oliver, 1941 -- one of the all-time classics on the earthworm. Dr Oliver was one of the first to harness the earthworm to the needs of the farmer and gardener, making highly fertile topsoil for optimum crop growth, and producing a constant supply of cheap, high-grade, live protein to feed poultry. He devised simple yet elegant and effective systems to bring costs and labour down and productivity up to help struggling farmers make ends meet. Oliver had an observant and critical eye and understood Nature's round. His ideas on the nature of modern food and health (or the lack of it) are only now being confirmed, half a century later. A delightful book. Full text online at the Journey to Forever Small Farms Library. Plus "My Grandfather's Earthworm Farm", "Eve Balfour on Earthworms", "Albert Howard on Earthworms", "The Housefly" by Roy Hartenstein.

Vermicompost and plants

Worm casts -- the best soil there is

Vermicompost consists mostly of worm casts (poop) plus some decayed organic matter. In ideal conditions worms can eat at least their own weight of organic matter in a day. In fact it seems they don't actually eat it -- they consume it, sure enough, but what they derive their nourishment from is all the micro-organisms that are really eating it. And yet -- mystery! -- their casts contain eight times as many micro-organisms as their feed! And these are the micro-organisms that best favour healthy plant growth. And the casts don't contain any disease pathogens -- pathogenic bacteria are reliably killed in the worms' gut. This is one of the great benefits of vermicomposting.

Chinese spinach seedlings grown with (from left) chemical fertilizer, powdered horse manure, vermicompost, and nothing.

Worm casts also contain five times more nitrogen, seven times more phosphorus, and 11 times more potassium than ordinary soil, the main minerals needed for plant growth, but the large numbers of beneficial soil micro-organisms in worm casts have at least as much to do with it. The casts are also rich in humic acids, which condition the soil, have a perfect pH balance, and contain plant growth factors similar to those found in seaweed. There's nothing better to put in your garden!

-- "Worms seem to be the great promoters of vegetation, which would proceed but lamely without them, by boring, perforating, and loosening the soil, and rendering it pervious to rains and the fibres of plants, by drawing straws and stalks of leaves and twigs into it, and, most of all, by throwing up such infinite numbers of lumps of earth called worm-casts, which, being their excrement, is a fine manure for grain or grass." -- The Rev. Gilbert White of Selborne, 1777

-- "All the fertile areas of this planet have at least once passed through the bodies of earthworms." -- Charles Darwin, "The Formation of Vegetable Mould through the Action of Worms with Observations on their Habits", John Murray, London, 1881


Worm castings are a rich, all-natural source of organic matter with lots of nutrients and moisture-holding capabilities. They are known to have an extraordinary effect on plant life. Castings improve the soil structure and increase fertility making them the most enriching soil conditioner available.



Worm castings have attained the highest attainable rating of EXCELLENT from an independent testing laboratory. The soil is odor free and will not burn. The high species diversity of microorganisms serves as a protector against disease as well as helps to control disease. In addition, the microorganisms break down soil nutrients making them readily available to plant root hairs. Castings also stabilize soil aggregates to enhance water-holding ability. They are high in nitrogen, phosphorus, potassium, calcium, magnesium, and trace minerals that are available immediately and time released for maximum results.


There are special plant growth enhancers as well that are only apparent in worm-worked soil. Studies show plants or seeds demonstrate the following attributes when grown in worm castings: greater plant height, leaf area, root mass, better germination and faster growth. Long-term benefits include improvement of soil and subsequent subsurface water quality. Earthworm Castings can be used to make worm tea to spray on soil and plants which multiplies the beneficial effects of the microorganisms.    

You need only use a small amount in or around your houseplants, vegetables and flowers. The miracles of the earthworm are easily seen in the beautiful growth and yields of your plants.


Extremely dark and rich in texture, tests have shown the nitrogen content to be 5 times greater than ordinary topsoil, the phosphate 7 times greater, potash 11 times, and magnesium 3 times. Castings will not burn even when applied directly to the most delicate plants. Definitely the finest soil conditioner available.


Great for use in your entire garden! Completely odor-free and 100 percent organic! Use for indoor plants as well.


Castings contain slow release nutrients which are readily available to plants. Castings contain the plant nutrients which are secreted by the earthworms. They dissolve slowly rather than allowing intermediate nutrient leaching. They are excellent for soil structure, porosity, aeration and water retention capabilities.


The activity of the earthworm gut is like a miniature composting tube that mixes, conditions, and inoculates the residues. Moisture, pH, and microbial populations in the gut are favorably maintained for a synergistic relationship, and then a terrific end product. Dr. Bill Becker, "The Benefits of Earthworms," Natural Food and Farming, July/August, 1991, p. 12


Earthworm castings are the best imaginable potting soil for greenhouses or house plants, as well as gardening and farming.


Earthworm castings will not burn even the most delicate plants and all nutrients are water-soluble, making it an immediate plant food. Earthworm castings, in addition to their use as a potting soil, can be used as a mulch so that the minerals leach directly into the ground when watered. The effects of earthworm castings used in any of these ways are immediately visible. They make plants grow fast and strong. Nematodes and diseases will not ruin gardens or plants if the soil is rich enough for them to grow fast. It is the weak plant in poor soil that is destroyed by nematodes and diseases. R.E. Gaddie and D.E. Douglas, Earthworms for Ecology and Profit, Vol. I "Scientific Earthworm Farming" 1975, p. 175.





Simple worm pile under bananas with burlap layer and shade cloth on top.

Makes bananas very strong.

Warning: Feeder roots thrive on/compete for castings!



The activity of the worm’s gut is like a miniature composting tube that mixes, conditions, and inoculates the residues. Moisture, pH, and microbial populations in the gut are favorably maintained for a synergistic relationship, and then a terrific end product. ~Dr. Bill Becker, “The Benefits of Earthworms,” Natural Food and Farming, July/August, 1991, p. 12



Worm castings are the best imaginable potting soil for greenhouses or house plants, as well as gardening and farming. Worm castings will not burn even the most delicate plants and all nutrients are water-soluble, making it an immediate plant food. Earthworm castings, in addition to their use as a potting soil, can be used as a mulch so that the minerals leach directly into the ground when watered. The effects of earthworm castings used in any of these ways are immediately visible. They make plants grow fast and strong. Nematodes and diseases will not ruin gardens or plants if the soil is rich enough for them to grow fast. It is the weak plant in poor soil that is destroyed by nematodes and diseases. ~R.E. Gaddie and D.E. Douglas, Earthworms for Ecology and Profit, Vol. I “Scientific Earthworm Farming” 1975, p. 175



http://kandmfarms.com/facts.html After a worm ingests organic matter, the material undergoes a change that is nothing short of a miracle. As Thomas J. Barrett once put it, "they (the worms) literally serve as colloid mills to produce the intimate chemical and mechanical mixture of fine organic and inorganic matter which forms their castings (excretions). In the mixing which takes place in the alimentary canal of the worms , the ingested materials undergo chemical changes, deodorization and neutralization, so that the resultant castings are a practically neutral humus, rich in water-soluable plant food, immediately available for plant nutrition."-(Harnessing the Earthworm, 1976)

Humus is beneficial to plants in at least three very important ways:

By "capturing" toxins which are present in the soil. Humus (which is organic matter) has a high capacity to fix heavy metals in materials such as sewage sludge, farmyard manures, crop residues and peat, preventing plants from "taking up" more of these compounds than they need, then later releasing them when they are required. By acting as a "buffer". Humus can help plants overcome soil pH levels that are either too high, or to low. An acid loving plant can still do well in a somewhat alkaline soil (and vice-versa), if large enough quantities of humus are present. This is due to the way humus prevents extreme pH levels from rendering soil nutrients "unavailable" to the plants.

As a growth stimulator. "Experiments on wheat, barley, potatoes, grapes, tomatoes, beets, and other crops show that even in very low concentrations, humic acids (contained in humus) act to stimulate plant growth. Tests to determine just how humic acids work revealed that they are in an ionically dispersed state. In this form they are readily assimilated by the plants as a nutrient, over and above any normal mineral nutrition that plants get. "-(The Rodale Book of Composting, 1992)

All of these benefits to plants, and more, are obtained by the presence of humus in the soil, and worm castings simply put, are biologically-active mounds that often contain as much as 40% more humus than is normally found in the top six inches of soil.

Are Worm Castings more nutritious than regular compost?

Yes! As material in a compost heap decays (becoming humus), the various nutrients undergo chemical changes which make them more accessible to plants. In addition to this process, however, worms also reduce the overall volume of the material even further as they remove the ingredients necessary for their own survival, growth, and reproduction (mainly bacteria, rotifers, etc.) Thus, with the remaining substances compacted into less volume, the actual nutrient percentages rise accordingly. It had been noted by several researchers that earthworm castings usually contain more "total and nitrate nitrogen, organic matter, total and exchangeable magnesium, available phosphorus, base capacity, and moisture equivalent" than their surrounding environment."-(C. A. Edwards and J. R. Lofty, in "Biology of Earthworms", 1977)~~http://kandmfarms.com/facts.html



From: http://www.ecobaby.ie/composting/vermicompost01.htm

Why is Worm Compost so good for plants?

The organic matter also undergoes chemical changes in the process. This make the nutrients more readily accessible to plant roots but in a form that is slowly released when required by the plants. Vermicomposting has this same effect on toxins, such as heavy metals found in sewage sludge. The process is called 'fixation' and it prevents plants taking up more than they need. Studies also show significant pathogen reduction in organic matter that has been through the vermicomposting process.

The vermicompost acts like a buffer for plants where soil pH levels are too high or low making soil nutrients available again to the plant The castings are much higher in bacteria, organic material and available nitrogen, calcium, magnesium, phosphorus and potassium than soil itself Vermicompost is biologically active and will continue to condition soils for up to 4 years.

Experiments in the US on tomato crops have shown that adding vermicompost will increase production by up to 33%.


How does Worm Composting work?

Vermicomposting is much more complex than worms simply eating and excreting organic material. It is a highly complex chain of chemical, biochemical and biological interactions and reactions. The whole process is based on natural systems which have evolved ov

er hundreds of millions of years. Worms play a vital role in creating the optimum conditions for the beneficial organisms to establish and reproduce. These 'good' organisms compete with and dominate the more harmful microbes. The waste is reduced in volume and increased in nutrient value. 

So who's responsible?

It takes more than just the worms to make vermicompost. The worms eat, chew and churn up the waste. The other organisms which accompany them also break it down. A simplified description of the overall mechanism is described below:

 1.    The worms ingest organic matter, fungi, protozoa, algae, nematodes and bacteria. This is passed through the digestive tract. The majority of the bacteria and organic matter pass through undigested (although the organic matter has been ground into smaller particles). This forms the casting along with metabolite wastes such as ammonium, urea and proteins. The worms also secrete mucus, containing polysaccharides, proteins and other nitrogenous compounds. Through the action of eating food and excreting their casts, worms create “burrows” in the material. This in turn increases the available surface area and allows aeration.

2.    There is an abundance of oxygen and nitrogenous compounds (urea, proteins and NH3) in the excreta (vermicast) and mucus secreted from the external tissues of the worms. Some bacteria require oxygen (aerobic bacteria) whereas some object to oxygen and prefer its absence (anaerobic bacteria). Anaerobic bacteria are responsible for the stench from stagnant drains, refuse sacks and landfill sites. With the aerobic conditions in vermicompost, aerobic microbiological growth increases. It is believed that the initial burst of microbiological activity mainly consists of nitrogen fixing bacteria, nitrification bacteria, and to a lesser extent, aerobic bacteria. This is based upon previously established information that burrow walls have a high proportion of the total nitrogen fixing bacteria and that casts have higher concentrations of soluble salts and greater nitrifying power. Accompanying this microbiological growth is the breakdown of organic nitrogen compounds to ammonia and ammonium.

The good news is that the sweet smelling aerobic process overcomes the ugly smell of anaerobes. That is why worm compost piles (properly fed and maintained) smell so nice!

3.    The whole process consumes organic matter and creates a ruffled surface in the burrow walls. The large surface area and improved aeration results in favourable conditions for obligate aerobes (such as Pseudomonas spp., Zoogloea spp., Micrococcus spp. and Achromobacter spp.). The continued growth of the microbiological population continues to increase the rate of decomposition of the material.

Air flows through the material more readily, minimizing the likelihood of anaerobic biochemical reactions occurring. This minimizes the formation of sulfide and ammonia gasses, odors that are typically present if anaerobic conditions are established. Objectionable odors disappear quickly, due to microorganisms associated with the vermicast

What about dangerous pathogens, enteric viruses and parasites?

Naturally, it is important that where potentially harmful organisms are in materials being composted, they should not be present in harmful numbers when the process is finished. With earthworm composting, this is indeed the case.  

The vermicomposting process has a profound effect on the levels of pathogens namely E.coli, Faecal Coliforms and Salmonella spp. with reductions of >99.9% possible. Material that is Vermicomposted exhibits greater pathogen reduction than that achieved with conventional composting. As all three of these pathogens are not obligate aerobes (that is requiring oxygen to survive, grow and multiply), it is likely that these organisms are subject to exploitative competition. The obligate aerobes namely Pseudomonas spp., Zoogloea spp., Micrococcus spp. and Aebromobacter spp. have evolved to process nutrients and reproduce at the highest efficiency in aerobic conditions and so the pathogens are excluded from nutrients and space as the obligate aerobes continue to increase under ideal conditions. 

A similar reduction in numbers exists for enteric viruses due to the lack of host species, exposure to a microbiologically active environment and the secretion of virucidal enzymes by the earthworms during the digestion process. An identical pattern is observed during the vermicomposting process when examining parasite Helminth ova) numbers, primarily due to the lack of host organisms and possibly direct digestion by the earthworms. 

Benefits of Vermicompost

The typical levels of the nutrients (N, P, K) in vermicomposted green waste are of the order of 1-2 %. It would appear that the vermicompost does not compare favourably with commercial chemical fertilisers however two important factors are overlooked when comparing the two, the microbial content and the organic matter content.

Chemical fertilisers are either sterile or have negligible microbiological activity. The chemical fertilisers are composed primarily of water-soluble chemical salts and as such organic material rarely forms part of chemical fertilisers. Once the salts have been depleted from a chemical fertiliser, then re-application is required to maintain the nutrient levels. The presence of nitrifying and nitrogen fixing bacteria in vermicompost means that nitrogen can be fixed from the atmosphere and converted to plant soluble nitrates.

The process continues as long as there is sufficient organic matter (which is present in vermicompost) and so re-application is not required at the same rate as chemical fertilisers. The ability of the microbiologically active vermicompost to regenerate the nutrients from the atmosphere, organic matter and water replaces those lost from chemical fertilisers by leaching, plant uptake and chemical reactions. In relation to moisture holding capacity and improvement of soil structure, chemical fertilisers have negligible effect, as they primarily consist of water-soluble salts. Vermicompost, on the other hand, due to the aggregate nature of the worm castings has appreciable water holding capacity and its use leads to improved soil structure. 

Vermicompost requires no curing (as traditional composted materials do) as it is already populated with beneficial microorganisms The overall time required (and hence the cost) for processing is therefore greatly reduced, and the process produces no toxic by-products or waste. The vermicompost itself is highly valued by gardeners all over the world and has a significant market value.









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