EARTHWORMS - The Benefits
Improve the physical structure of the soil
- improve water filtration rates and absorption rates helping the soil to drain better. Less runoff equals less watering and less erosion.
- the tunneling activity improves soil aeration, porosity, and permeability.
- increase moisture absorption and moisture available to plants. Castings absorb water faster than soil, castings hold more water than equivalent amounts of soil. Bhawalker Earthworm Research Institute
- castings have the ability to absorb moisture from the air and hold it in a manner that plants can use. Bhawalker Earthworm Research Institute
- 25 earthworms per square foot of soil equal 1 million earthworms per acre. Studies in England have shown that in healthy soil forty tons of castings per acre pass through earthworms bodies daily. A new USA study indicates 1½ million worms per acre which move 20 tons of earth each year.
- studies have shown that with good food sources and favorable conditions, a field might have over 100 nightcrawlers per square yard. National Soil Tilth Lab
- One earthworm can digest 36 tons of soil in one year. US Soil Conservation Office
- the tunneling activity of worms helps breakup hardpan and other compacted soils.
- studies have shown that 30% of a fields respiration during cold wet winter-spring months are due to earthworms.
- A study in European orchards found that earthworms could increase the pore space in soil by 75-100% and that earthworm burrows accounted for _ of a soils air-filled pores. Earthworm Ecology and Biogeography in North America, 1995.
Improve soil fertility
- bring up minerals from deep in the subsurface that are often in short supply in surface layers
- earthworm activity counteracts leaching by bringing up nutrients from deep in the soil and depositing them on the soil's surface as castings
- the burrows also allows roots to easily go down deeper into the soil and get nutrients they could not ordinarily reach
- removes litter from soil surface - earthworms eat the litter and leave the nutrients in their castings for plants to use as a natural fertilizer that is non-polluting.
- help compost residues and waste products, bacteria in a worm's gut help destroy harmful chemicals and breakdown organic wastes
- create fertile root channels - the mucus lining of abandoned burrows are an excellent source of nutrients
- make plant nutrients more available, worms concentrate minerals in their castings in a form that is easy for plants to absorb
- earthworms chelate nutrients, making minerals available to plants that would otherwise be in a form that would be chemically unavailable.
- worms stimulate microbial populations, nitrogen fixing bacteria are more numerous near earthworm burrows and in their castings. One study on bacteria and actinomycetes found densities from 10-1,000 times greater. Earthworm Ecology and Biogeography in North America, 1995.
- plant growth stimulants such as Auxins are produced in the castings, these hormones stimulate roots to grow faster and deeper.
- worms neutralize soil pH, cast analysis shows that the product coming out of the back end of a worm is closer to neutral than what goes in the front end.
- Analysis of earthworm castings reveal that they are richer in nutrients than surrounding soil, often 3 times more calcium, several times more nitrogen, phosphorus, and potassium. K.P. Barley, Advances In Agronomy, Vol. 13, 1961
- nitrogen fixing bacteria live in the gut of earthworms and in earthworm casts and higher nitrogenase activity, meaning greater rates of nitrogen fixation are found in casts as compared to surrounding soil.
- One study found that earthworms are responsible for passing nitrogen to the soil at a rate of 100 Kg N per ha per year. Earthworm Ecology and Biogeography in North America, 1995.
- The earthworms gut is a natural bioreactor, which increases the beneficial microbial density in the material it excretes to 1,000 times that of the surrounding soil. Worm Digest, Winter 1994.
Improve plant growth and health
- Tests have shown that crops grown in earthworm-inhabited soil increased yields from 25% to over 300% than in earthworm-free soil. K.P. Barley, Advances in Agronomy, vol. 13, 1961, p. 262-264
- earthworms help eliminate thatch in lawns and grassy areas by eating and digesting the plant debris
- studies have shown that soils rich in earthworms have less of the harmful nematodes
- earthworms create soil conditions that discourage populations of soil organisms such as insects, nematodes and others that are harmful to plants
- by passing soil and organic matter through their bodies, gradually make acid soil less acid and alkaline soil less alkaline. The Rodale Book Of Composting, 1993
- A recent study found that earthworm produced compost (vermicompost) dramatically increases germination and growth in many plants. Adding only 5% of the compost to commercial growing media (95%) significantly increased plant growth. Dr. Clive Edwards, Ohio State University, Nursery Management & Production, January 1995
- Research has shown that twice as many roots grew in pure worm castings than in sphagnum. Dr. Clive Edwards, Ohio State University
- Many species of earthworms actually eat the bad microbes (fungi, bacteria, etc.) that are plant pathogens and in the process they also increase the good beneficial microbes.
- It has recently been discovered that in feeding, earthworms consume spores of mycorrhizae, a beneficial fungi that help roots take up nutrients. These spores are deposited in the worm castings, deep in their burrows, where roots easily find them as they grow. The Avant Gardener, p. 87, 1995.
- Studies have shown that earthworms can increase barley yields 78-96%, spring wheat and grass yields 400%, clover yields 1,000%, and peas and oats by 70%. Other studies found that yields were increased for millet, soybeans, lima beans, and hay. Studies in New Zealand found that earthworms at least doubled yields in all cases and adding worms to crops has become standard agricultural practice. Earthworm Ecology and Biogeography in North America, 1995.
- Experiments at Tennessee Technological University found that 10% vermi-compost in a potting mix improved the germination of seeds of low viability (Echinacea purpurea) by 43%
- Researchers at Ogun State University have found that a tea made from the worm castings speeds up the sprouting of hard to germinate seeds following a 1 hour soaking
A large earthworm population suppresses weed growth
- the tunneling activity of earthworms prevents many of the conditions that weed seeds need to germinate
- earthworms often eat weed seeds and either destroy them or reduce their ability to germinate
- earthworms stimulate the growth of microorganisms in the soil and some weed seeds are destroyed by these microorganisms
- some microorganisms (bacteria and fungus whose growth is stimulated by worms) live in a symbiotic relationship with plant roots and help plants grow better hence shading out weeds and out competing them for water and nutrients.
Worms often help clean up dangerous chemicals in the environment
- Researchers have found that bacteria living in the guts of worms breakdown (detoxify) many hazardous chemicals such as hexachlorocyclohexane (HCH), organic gardening may/june 1993
- microbes living in worms have the ability to breakdown complex organic molecules like cellulose and lignin
Improve water absorption and prevent erosion
- increase the water stability of the soil, earthworm castings can take a direct hit by a raindrop and maintain their shape, this reduces erosion and runoff hence helps the soil absorb water
- A research study conducted in Minnesota, showed that earthworms added to cornfields increased water absorption rates 35 times over control fields without the earthworms, within a 6 week period. Acres USA, March 1994.
- Soil in a field with 100 nightcrawlers per square yard, 2 inches of water (a very heavy rainfall) could be absorbed by the soil in 12 minutes. The same soil without earthworms took over 12 hours to absorb that much water. National Soil Tilth Lab
- If the top 3 feet of soil contained 25% macropores (earthworm burrows) then that soil should be able to absorb at least a 9 inch rainfall without runoff. Natural Food & Farming, July/August 1991.
- One study showed that on a sloping field with no-till practices, there were 155 earthworms holes per square yard and an average runoff of 0.08 inches per year. This compares to a tilled field with 6 holes per square yard and 4.9 inches of runoff per year. The average rainfall for this area is 39.4 inches. Natural Food & Farming, July/August 1991.
- Scientists from the Agricultural Research Service found that grass and leave mulched plots had twice as many earthworms as those mulched with cornstalks. Water penetrated the earth-worm filled soil up to 4 times faster.
- Chemicals produced in the earthworm cause the castings to form aggregates in the soil that are resistant to erosion.
- Studies have shown that earthworms in soils can easily triple infiltration rates and cut run-off in half. Earthworms In Agroecosystems, 1995.
- Some scientists now believe that earthworms have the potential to eliminate soil erosion! This could save society billions of dollars in erosion control, reduce pollution from dangerous synthetic chemicals and improve the environment.
- in an acre of good soil researchers have found more than 1 million worms and 1,200 miles of earthworm holes or burrows.
Earthworms are valuable
- one-million earthworms per acre is about 25 earthworms per square foot of soil. If one had 1 nightcrawler per square foot at a value of $1.00 per dozen then one would have $3,630 worth of earthworms. Full retail value of one million earthworms would be over $83,000. If earthworms would work only 100 days per year and eat their weight of soil and/or residues daily, then at that rate with 1 ton of earthworms per acre you would have 100 tons of earthworm manure (castings) per acre per year. This is about 2/3 inch deep layer over an entire acre of land. Natural Food & Farming, July/August 1991.
- One million earthworms will have burrows which will have the equivalent space of 4,000 feet of 6 inch drain tile. At a installed price of $1.20 per foot for drain tile, those burrows are worth $4,800 per acre. Natural Food & Farming, July/August 1991.
- Soil samples from a field not fertilized for 5 years but with a active earthworm population was analyzed. Based on the reported analyses it was found that 100 tons of earthworm castings will contain 4 lbs. of nitrate nitrogen, 30 lbs. of phosphorus, 73 lbs. of potassium, 90 lbs. of magnesium, 500 lbs. of calcium. That is the equivalent to a
4-69-86 fertilizer and 3/4 ton of limestone worth $34.15 per acre with no fee for spreading or transportation.
- Research presented at the ISEE 5 (International Symposium on Earthworm Ecology at Ohio State University) point at earthworms being a important biomedical resource. It has been found that ingredients from earthworms have anti-cancer properties.
- the bodies of earthworms are extremely nutrient rich from minerals to amino acids, proteins and vitamins. When earthworms die these nutrients are released into the soil.
How to attract and promote earthworms
- Mulch all soil with organic mulches which help stabilize soil temperature and moisture.
- Mulch provides food and shelter for earthworms. Compost is an excellent mulch and as a soil amendment to attract (food source) earthworms.
- DO NOT USE DANGEROUS SYNTHETIC CHEMICALS:
Agricultural chemicals such as salt based fertilizers (i.e. 13-13-13), pesticides, etc. can kill earthworms. Even if a few pesticides do not kill earthworms, such as DDT, birds are killed when they eat the worms. Pesticide Reviews, Vol. 57, 1975.
earthworms and other beneficial organisms are destroyed by synthetic chemical fertilizers and fungicides, pesticides, etc. (Reviews of Environmental Contamination and Toxicology, 1992). In the absence of earthworms, the soil becomes lifeless, sterile, and nutrient deficient.
- Studies have found that most organic fertilizers tend to have a positive effect on earthworms and increase population densities. Earthworm Ecology and Biogeography in North America, 1995.
- soils that are not tilled have 3-4 times as many nightcrawlers (surface feeding earthworms) as soils that are tilled in the spring or fall. Tilling greatly accelerates the breakdown of organic matter in the soil that worms need. National Soil Tilth Lab
- studies have shown that mulches produced from grass cuttings or leaves have twice the earthworm population than course mulches from straw or corn stalks, etc. National Soil Tilth Lab
- mulches made from wood wastes that have lots of "fines" or small particles sizes are easier for worms to use (swallow and eat). The increased particle surface area of the small sizes also allows for greater microbial activity that is preferred by worms.
- rough (unfinished) compost is one of the best worm-food mulches there is. The Avant Gardener, p. 87, 1995.
Types of earthworms
- over 3,000 worm species have been identified. Experts disagree as to what distinguishes one type of worm from another and if one species is a true earthworm or not. All soil worms are beneficial and most references lump all soil worms into the category of "earthworms".
- Two basic types of worms, those that feed on the surface and those that feed in the subsurface. The surface feeders eat plant residue, are generally large worms and live in vertical burrows often over 6' deep. Subsurface feeders are smaller than surface feeders like nightcrawlers but outnumber them 9 to 1. They eat their way through the subsurface loosing, aerating and improving soil structure in the process.
When worms are separated into "worms" and "earthworms" then following applies:
- Redworms, often called manure worms, brandling worm, or red wigglers, they are reddish brown in color, they live in the soil in the surface layer of decaying vegetation (litter). They feed on this layer, multiplying rapidly in numbers, expand into poorer surrounding soil and die thereby distributing the nutrients contained in the excess wastes over a larger area. Often used in small scale worm bins. Eisenia foetida and Lumbricus rubellus (tends to be more soil dwelling if large amounts of organic material are in the soil) are examples of redworm species.
- Earthworms, often called soil processing worms, they are a burrower, a soil processor, eating dead organics and rock particles, grinding and excreting them as a finely ground mix which serves as food for bacteria. They tend to survive in harsh conditions better than redworms. They do not assimilate the organics to the same extent as redworms for themselves, hence they do not multiple as quickly as redworms whose assimilation rates are much higher. The higher rate of assimilation (redworms) means that the nutrients consumed by the redworms goes into building their own biomass while the earthworm passes on these nutrients in a soluble form in their castings.
- Pheretima elongata, deep burrowing earthworm used in Bombay India to convert garbage into vermicompost. Recommended by Uday Bhawalker (Bhawalker Earthworm Research Institute) as the most efficient organic waste converter. Waste conversion occurs at the soil surface, not in a bin hence less material handling is required.
- Lumbricus terrestris, called nightcrawlers, dew worms, rain worm, orchard worm, etc. They like soil temperatures less than 50°F. They are also dig burrows and do not like to have their burrows disturbed. They come to the surface to feed on dead grass leaves etc. drawing them into their burrow hence taking organic matter deep into the soil layer. A good garden worm.
- Garden worms, Allolobophora caliginosa, A. chloritica, Aporrectodea turgida, A. tuberculata, etc. often found in pastures.
- most worms found in U.S. soils are not native
Some earthworms from the southern hemisphere can grow 3-5' long, 1" in diameter and weigh up to 1.3 pounds
Earthworms have many uses from soil farmer to food for animals. Most recently they are being used as a diagnostic tool since they have the ability to hyperaccumulate toxins and environmental pollutants found in the soil (since they ingest soil). As a result they are often collected and their tissue analyzed for chemical contaminants
25 earthworms/sq. ft. = 1 ton of worms/acre
1 ton worms = 100 tons of castings or _" manure (castings) on surface per acre
Macropore equivalent to 4,000ft. of 6" tile drain pipe per acre
Nutrients added to 1 acre of soil each year:
4 lbs of nitrate of nitrogen
30 lbs of phosphorus
72 lbs of potash
90 lbs of magnesium
500 lbs of calcium
or in terms of a fertilizer analysis = 4-68-96 plus 3/4 ton of limestone for a nutrient value of $34.15/acre
The Biology of Earthworms, C.A. Edwards and J.R. Lofty
Earthworms, K.E. Lee
Worms Eat My Garbage, Mary Appelhof, ISBN 0-942256-03-4
Worm Digest Magazine, P.O. Box 544, Eugene, OR 97440-9998
The Farmer's Earthworm Handbook: Managing Your Underground Moneymakers, David Ernst, Lessiter Publications, Brookfield, Wisconsin. 1995.
"Worm Wise News", International Worm Growers Association,
P.O. Box 900184, Palmdale, CA 93590
Soil Biology & Biochemistry, Special Issue: 5th International Symposium on Earthworms Ecology, ISSN 0038-0717
Earthworm Ecology, Soil and Water Conservation Society, Edited by Clive Edwards, PhD, St. Lucie Press, Copyright 1998, ISBN: 1-884015-74-3
SOURCES OF WORMS:
Twin Oaks Farm (Georgia Brown Nose...a heat tolerant worm)
Rt. #1 Box 78A
Purdon, Tx 76679-9801
Rabbit Hill Farm
Rt. 3 Box 2936
Corsicana, Tx 75110
City of Grapevine
Pat's Worm Ranch (Louisiana Wigglers - soil worm..not for containers)
Sonny or Pat Kellum
P.O. Box 3194
San Antonio, Tx 78211
Brown's Worm Farm
Marietta, OK 73448
Flowerfield Enterprises (good source of educational material for children)
Mary Appelhof ("The Worm Lady")
10332 Shaver Road
Kalamazoo, MI 49002
Rt. 2 Box 183
Eudora, AR 71640
Southern Worm Enterprize
12118 Marilyn Lane
Hammond, LA 70403
Willingham Worm Farm
Rt. 1 Box 241
Butler, GA 31006
SOURCES OF WORM BINS & OTHER INFORMATION:
Gardener's Supply Company
128 Intervale Rd.
Burlington, VT 05401
5100 Schenley Pl.
Lawerenceburg, IN 47025
Peaceful Valley Farm Supply
P.O. Box 2209
Grass Valley, CA 95945
Fallbrook, CA uses brandling worms "Eisenia foetida" and red worms "Lumbricus rubellus" for vermicomposting. Vermicomposting beds are 8' wide and 200 hundred feet long. Static pile compost (about 30 days of heat treatment for pathogen destruction) is then transferred to the vermicomposting beds for 60-90 days. The compost is mixed with straw and layered in 3 inch thick on the bed, it is then seeded with about 1 pound of worms per cubic foot of compost. The worms are given 1 month to acclimate themselves to the new environment then 4-6" of sludge compost is applied to the beds every week. About once a month additional straw is added to maintain porosity. The worms feed on newly applied compost and deposit castings in the lower layer. Water is added as needed. Compost is applied continuously until about 3 feet high. The worms are concentrated in the top 6-8" the rest of the pile is stabilized vermicompost. The top section with the worms are transferred and the process starts again. The earthworm population doubling time is about 60-90 days. From the "Reuse of Sludge & Wastewater residuals by Alice Outwater, p. 118".
The processing of organic wastes is most rapid between 60-79°F (15-25°C) and 70-90% moisture content.
Pre-composting of wastes can disperse salts and ammonia of which earthworms are very sensitive. A good example is bio-solids.
A number of worms have been used in vermicomposting, the most common is Eisenia feotida (the tiger or brandling worm). Other suitable species include Lumbricus rubellus (the redworm), Eudrilus eugeniae (African Nightcrawler), and Perionyx excavatus (Asian species). Each species has particular favorable characteristics hence it is important to choose the right one for the feedstocks being composted.
Lufkin Texas, call...Ed Green - vermicomposting of sewage sludge
Oregon Soil Corporation April 11, 1996
1324 Beaver Lane
Oregon City, Oregon 97045
Dan Holcombe (503) 557-9742 658-8342 260-8232
- If windrows use 12' earthen berm around windrows and 3 layers of 50% shade cloth for temperture control, 2-3' chip base with perferated pipe for ventilation, also mist system useful (moisture and temperature control)
- his system yeilds 5-6 lbs. of worms per cubic foot
- if pH around 6.8 then no fly problem
- a grocery store will generate 400-800 lbs/day/store depending on local growing season
- more protein in 1lb of worms than 1 lb of steak
- student at Ohio State doing disertation on worm castings
Allolobophora chlorotica - the green worm, native to U.S.
Aporrectodea rosea - the pink soil worm, native to U.S.
Aporrectodea trapezoides - the southern worm, native to U.S.
Aporrectodea turgida - the pasture worm, native to U.S.
Bimastos tumidus - often found in compost piles, tolerates medium C:N ratios and cooler temperatures better than Eisenia foetida , multiplies rapidly in old straw and spoiled hay, hardy to Z-5 and will survive in ordinary soil conditions hence once established it would survive without extensive preparations. Earthworm Ecology and Biogeography in North America
Eisenia foetida: (the tiger or brandling worm), often used for composting sometimes called E. andrei, (composter or surface worker species)
Eudrilus eugeniae: (African nightcrawler) do well but cannot withstand low temperatures.(composter or surface worker species)
Hyperiodrilus africanus: (west African)
Lumbricus rubellus: (common redworm or red marsh worm), used in Cuba's vermicomposting program, (composter or surface worker species), native to U.S.
Lumbricus terrestris: nightcrawler, native to U.S.
Perionyx excavatus: (Asian species) do well but cannot withstand low temperatures. (composter or surface worker species)
Octolasion tyrtaeum - woodland white worm, native to U.S.
- bigger, stronger and livelier than common species such as red worm (esienia foetida). It is a deep burrowing worm. Recently found in Missouri. Agricultural Research Service scientists are attempting to breed and spread this species as it would be useful for breaking up hardpans and for erosion control (increase infiltration). Avant Gardener, p.87, 1995.
- deep burrowing earthworm used in Bombay India to convert garbage into vermicompost. Recommended by Uday Bhawalker (Bhawalker Earthworm Research Institute) as the most efficient organic waste converter. Waste conversion occurs at the soil surface, not in a bin hence less material handling is required.
Ponotscoex corethrurus: (common through-out humid tropical zone)
Earthworms (deep dwellers): talk by Mary Applehoff
Aporrectodea caliginosa -
A. trapezoides -
A. rosea -
A. longa -
castings weigh about 800 lbs/cy
Vermi composting: use 8 parts waste to 1 part worms, Clive Edwards, Ohio State
Artioposthia triangulata - "flatworm", from New Zealand, destroying earthworms in Great Britain, worm is dark brown, flattened with cream speckled margins, likes moist conditions with moderate to cool temperatures.
Australoplana sanguinea - "flatworm", from Australia, destroying earthworms in Great Britain, tolerates warmer and drier conditions than A. triangulata