“Biological Agriculture” relies on earthworms and other soil critters to do what plows and synthetic chemicals do in conventional agronomic systems. Follow the advice below to encourage worm populations in your fields:
–> There are many species of earthworms around the world. The most common agricultural species in North America and Europe are the Common Garden Earthworm = Nightcrawler = Lumbricus terrestris, and the Manure Worm = Redworm = Eisenia foetida. These are the most prevalent species sold by worm hatcheries for fish bait and farming.
–> Nightcrawlers dig vertical burrows deep into the subsoil. At night the worms rise to the soil surface to feed = they drag bits and pieces of leaves and other organic matter down into their tunnels. Walk through a field at night with a flashlight and you will see many earthworms.
–> Manure worms live close to the soil surface and do not dig vertical burrows. Redworms are specialized to eat manure and so they are rarely seen except around the base of compost piles or in fields where many animals graze.
–> 31 nightcrawlers or manure worms per ounce; 500 worms per pound; 1,000,000 worms = 2,000 pounds = 1 ton. 1 average earthworm (Lumbricus terrestris) or manure worm (Eisenia foetida) from a commercial hatchery weighs 0.002 pound = 0.032 ounce = 0.9072 gram.
–> Active, adult earthworms (Lumbricus terrestris) eat their body weight in soil and organic matter daily. Sluggish worms, immature worms, and worms of other species may eat only 10% to 30% of their body weight each day. 1,000,000 common earthworms per acre (about 23 worms per square foot of topsoil 12 inches deep) = 1 ton of earthworm castings = worm manure DAILY during the growing season.
–> Usage Note: 1 earthworm cast, 2 earthworm casts, many earthworm castings.
–> Average daily worm cast is about 0.90 gram although weight of surface casts is considerably greater and varies widely. Average surface cast weight is approximately 10 to 14 grams or about 0.30 to 0.50 ounce. Surface worm cast weight ranges up to about 2 ounces in temperate climates and considerably more in tropical areas, depending on worm species, soil type, and available food. For example, 1 average adult earthworm (2 to 3 years old) living in a bed of compost in a tropical climate can produce 10 pounds = 4.54 kilograms of castings annually ~ 12.4 grams ~ 0.43 ounce of castings daily.
–> Average surface cast volume is approximately 1 Tablespoon = 15 milliliters (plus or minus 7 milliliters).
— > Earthworms are most active in early spring and mid fall when weather is cool and moist. Ideal soil temperature = 65 degrees Fahrenheit. Earthworms are less active during hot, dry summer months. Earthworms rise to the surface to feed at night then sound to lower soil depths each morning when temperatures rise.
–> Do not plow in spring or fall if practical as this kills many worms. Do not plow, cultivate, or spray in early evening, after dark, or early in the morning as this kills many worms. The best time to till, cultivate, or spray is in the afternoon when temperatures are highest and worms have retreated to cooler soil depths.
–> Keep fields planted with cover crops in spring and fall to feed worms. They need much food at this time.
–> Don’t leave soil bare over winter. Protect winter fields with an insulating blanket of crop residues, mulch, or cover crops. 1 or 2 inches of organic matter can double earthworm populations.
–> Earthworm populations increase in direct proportion to the amount of organic matter on the soil surface = leaves, twigs, straw, et cetera. More cover = more protection & more food = higher worm populations. Keep the soil mulched or covered with growing plants at all times. 2 inches of mulch double worm populations compared to cornfields where whole stalks are left on soil surface.
–> Baby earthworms when they hatch from their cocoons = egg cases are very small, only 1/2 to 3/4 inch long. Earthworms are extremely vulnerable when first hatched. Do not plow, cultivate, or spray when worms are hatching.
–> Earthworms need protein in their diet. Worm populations double on legume fields compared to grass fields. Earthworms especially favor clovers, particularly white clover. Include legumes in field rotations, pastures & hay fields, cover crop mixes, and living mulches.
–> Earthworms breed and grow very slowly. Baby worms take 2 to 3 years to mature. A plentiful, steady food supply is essential to support maximum breeding and population growth. More organic matter (roots, stems, leaves) = more food = faster population growth = more worms.
–> Earthworms do not spread rapidly. A worm colony might spread 3 feet in a year. That’s as fast as earthworms go. To “seed” worms drop 6 nightcrawlers every 30 feet then immediately cover with a generous heap of mulch, compost, or manure = whatever worms are used to eating. It takes at least 10 years for worm colonies spaced 30 feet apart to spread across an acre-sized field. 1 acre = 43,560 square feet = 4,840 square yards ~ 0.404 hectare.
–> Adult worms are particularly sensitive to dietary changes. For example, worms raised in hatcheries die if placed in corn fields because they have problems adapting to new, strange foods.
–> Do not try to seed Manure Worms = Eisenia foetida in crop fields. The manure worms will die because they are not adapted to this environment. Use only nightcrawlers = Lumbricus terrestris for agricultural development, mine reclamation, terraforming, reforestation, and similar environmental restoration projects.
–> If you need to seed worms, talk to the hatchery and ask for their best deal on earthworm cocoons. Baby worms adapt quickly to any food available. Mix egg cases gently with screened peat moss, corn meal, sifted compost, or similar carrier then “plant” with a common grain drill.
–> Switching from conventional tillage to no-till does not happen overnight. Conversion speed is entirely dependent on earthworm food supplies. There is no solution for worms’ low natural reproduction rates. Buying more worms or egg cases won’t make the process go any faster. You can’t fix this problem by throwing money at it. Patience is required. You won’t see substantial improvements in soil structure or fertility until the fourth or fifth year of no-till ~ 2 earthworm generations. Dramatic differences become smack-upside-the-head obvious by the 7th or 8th year without plows ~ 4 worm generations. Conversion speed is controlled by how many tons of organic matter are added to each field. Start looking at crops in terms of their biomass production. This game is all about weight. The farmer with the most tons wins!
–> Tillage kills earthworms. Loses depend on plow type, tillage depth, and time. Chisel plows are the most destructive, disk plows slightly less so. Old fashioned moldboard plows are the least destructive of all conventional tillage implements. Chisel plows kill 3 times as many earthworms as moldboard plows.
–> RULE: Less tillage is better than more tillage. Shallow tillage is better than deep tillage. “Warm tillage” (afternoon & summer) is better than “cool tillage” (spring, fall, morning, evening, and night).
–> Till just enough to get your crop in the ground. Disturb the soil as little as possible. All you need is a small hole to set transplants or a narrow slot to sow seeds. It is rarely necessary to till more than 2 inches deep (unless you are planting potatoes).
–> No-Till is better than strip till which is better than ridge till which is better than whole surface conventional plowing.
–> Rear mounted rototillers are ideal tools for shallow tillage. For example: Broadcast winter wheat and Dutch White Clover = Trifolium repens into standing weeds or cover crop. Mow vegetation then rototill only 2 inches deep to get seeds into the ground. Irrigate to firm seedbed or wait for rain. Your field will look rough and trashy but the litter is necessary to prevent wind and water erosion. Some seeds will be buried too deep, others too shallow, but enough will germinate and survive to produce a good crop. If soil is too wet, omit rototilling. You will still make a profitable crop. Small seeds do not absolutely need to buried in earth. Cut weeds or nurse crop will cover and protect seed.
–> Earthworms do not “like” to eat maize leaves and they especially dislike whole corn stalks and cobs. Continuous corn = planting maize in the same field year after year reduces earthworm populations to minimal levels. For best results use a stalk chopper or forage chopper to shred dead corn plants so they decompose faster. Plant maize into a living mulch of Red Clover = Trifolium pratense or other nitrogen fixing legume. Follow corn with fall turnips or other cover crop to feed and protect worms over winter. Rotate corn with legumes or other broad leaf cover crops. Do not follow maize with a grass or cereal crop unless also planted with a companion crop of clover or other legume. Broad ecological diversity favors large earthworms populations. Translation: Worms like a varied, balanced diet.
Example: Plant forage maize at 80,000 to 100,000 seeds per acre to kill weeds. Flatten with a roller-crimper or cut with a sickle bar mower after 70 days (18 tons biomass) or approximately 110 days (30 tons biomass per acre). This is called Mulch-In-Place. Direct seed pumpkins or squash through the corn mulch with a no-till seeder. At the same time, broadcast Dutch White Clover = Trifolium repens or other low growing legume over field. Clover fills any gaps in the mulch and provides earthworms with a “balanced diet”. Result: 95% or better weed control and few insect pests. Mulch keeps fruits clean so farmer gets premium prices for his pumpkins.
Note: Mulch-In-Place is used to grow crops without herbicides. Popular mulch crops include Winter Rye = Cereal Rye = Secale cereale in temperate climates and Sunn Hemp = Crotalaria juncea in tropical and subtropical climates.
–> Adult earthworms can live 9 or more years in captivity. How long worms live in the wild is unknown.
–> Worms constantly maintain their burrows which often extend 5 to 6 feet into the subsoil. About the diameter of a pencil, worm holes are essential for aeration and drainage of natural soils. Fields with populations of 1 million earthworms per acre typically contain approximately 900 to 1,200 MILES of tunnels. These tubes are lined with “earthworm cement”, a natural glue that keeps tunnels open many years after resident earthworms have died. Plant roots follow earthworm burrows deep into the subsoil where moisture levels are relatively constant. This is why crops grown in biologically managed fields have considerable drought resistance. (Crop roots also follow weed roots into the subsoil, especially weeds with deep taproots. This is why melons grown in weeds make a crop in dry years while clean cultivated vines shrivel and die).
–> If agricultural wastes are plentiful earthworms can be fed just like crop plants on an irrigation schedule. Apply weed seed meal, spoiled corn meal, dried brewer’s grains or similar DRY organic “fertilizer” at 2 Tablespoons (1/8th cup) per square foot ~ 1 ounce per square foot ~ 5 pounds per 100 square feet ~ 1 ton (2,000 pounds) per acre. Apply WET materials like spent brewer’s grains or fresh cow manure at 8 Tablespoons (1/2 cup) per square foot ~ 4 ounces per square foot ~ 25 pounds per 100 square feet ~ 5 tons per acre. Broadcast worm food on soil surface. Reapply as needed when food is eaten = no longer visible on soil surface.
–> Ammonia based nitrogen fertilizers kill earthworms. The worst form is anhydrous ammonia gas. Liquid ammonia fertilizers are far less injurious. Note: Organic fertilizers can also be lethal. Excessive amounts of manure lagoon effluent decimate worm populations. It is good practice to irrigate before applying ammonia or any fertilizer, chemical or organic. (Irrigation prevents plants from absorbing too much fertilizer at once. Over-fed plants attract insect pests).
–> RULE: Chemical fertilizers (or manure lagoon effluents) are best applied in small amounts throughout the growing season, ideally diluted in irrigation water. For best results do not apply fertilizers to bare soils; apply nutrients only to growing plants. Earthworms are quite sensitive to concentrated chemicals, organic or synthetic.
–> To stabilize ammonia in animal manures mix with 5% phosphate rock powder by weight (100 pounds of phosphate rock per ton = 2,000 pounds of manure). Store under cover until needed. Spread or incorporate manure on field then immediately seed with Buckwheat (Fagopyrum esculentum) or other phosphorous absorbing cover crop. (Mixing phosphate rock with manure greatly increases phosphate availability to crops. Organic acids in manure make phosphorous soluble).
–> Concentrated chemical fertilizers (especially nitrogen) decrease soil organic matter and earthworm populations. Spread supplementary organic matter on fields where chemical nutrients are applied. Whenever practical use organic fertilizers to encourage earthworm growth.
–> How Earthworm Populations Vary by Soil Type and Land Use
50,000 worms/acre ~ 1 worm/square foot: Moldboard Plowed Continuous Corn; Acid Peat Soils.
80,000 worms/acre ~ 2 worms/square foot: No-Till Continuous Corn with Herbicide.
150,000 worms/acre ~ 3 worms/square foot: Fine Gravel Soils; Coarse Sandy Soils; Medium & Heavy Clay Soils.
170,000 worms/acre ~ 4 worms/square foot: Bare Earth Orchards (Conventional Cultivation); Alluvial = Silt Soils; Light Clay Soils; Heavy Loam Soils.
225,000 worms/acre ~ 5 worms/square foot: Medium Loam Soils; Fine Sandy Soils.
250,000 worms/acre ~ 6 worms/square foot: Chisel Plowed Corn & Soybeans Rotation; Chisel Plowed Continuous Soybeans; Light Loam Soils.
500,000 worms/acre ~ 12 worms/square foot: No-Till with Herbicides.
650,000 worms/acre ~ 15 worms/square foot: Moldboard Plowed Continuous Soybeans.
1,000,000 worms/acre ~ 23 worms/square foot: Biological No-Till (Rye Mulch-In-Place); Orchards with Mixed Grass & Legume Sod; Undisturbed Tall Grass Prairies & Hay Fields; Natural Alpine Meadows.
1,300,000 worms/acre ~ 30 worms/square foot: Biological No-Till with Mixed Species Cover Crops; Fields Fallowed 5 Years (Mostly Broad Leaf Weeds).
2 million worms/acre ~ 46 worms/square foot: Continuous Clover Living Mulch; Organic Gardens; Dairy Pastures; Manure Fertilized Fields (22 Tons per Acre Yearly).
3 million worms/acre ~ 69 worms/square foot: Year-Round Mulch 8 Inches Thick (Vineyards & Berry Farms); Sheet Composting 12 Inches Thick (Orchards); High Humus Organic Gardens; Raised Beds Filled with Compost, Leaf Mold, or Manure.
4 million worms/acre ~ 92 worms/square foot: Undisturbed Temperate Deciduous Forests with Deep Leaf Litter; Intensively Grazed Alpine Pastures.
5 million worms/acre ~ 115 worms/square foot: Temperate Rain Forests in Oregon & Washington.
6 million worms/acre ~ 138 worms/square foot: Intensive Rotational Grazing Dairy Pastures; Manure Fertilized Fields (44 Tons per Acre Yearly).
7 million worms/acre ~ 161 worms/square foot: Greenhouse Beds 3 Feet Deep Filled with Composted Manure.
8 million worms/acre ~ 184 worms/square foot: New Zealand Sheep Pastures (Intensive Rotational Grazing).
Note: Numbers are approximate. Expect considerable variation between countries, climatic zones, elevation above sea level, and land management practices. Earthworms do not thrive in acidic soils, poorly drained soils, rocky or sandy soils, or tight heavy clays. The most important environmental factor for earthworm survival is ORGANIC MATTER. Earthworm numbers increase or decrease dramatically depending on the amount of available food. Highest populations occur on soils where plants grow year-round, and on soils covered with substantial depths of leaf litter or other plant materials. To estimate worm populations use a tape measure and straight-edged garden spade, dig a 1 cubic foot soil sample, then carefully break apart the soil and tally earthworm numbers. Multiple samples per acre yield more accurate estimates.
–> 1 million earthworms per acre is the Holy Grail for most farmers. This goal is unreachable with conventional farming practices. To increase worm populations on a field-scale basis requires a long-term soil conservation strategy including crop rotations, cover crops, living mulches, and reduced tillage. Additional measures such as improved drainage (vertical mulching or tile lines), increased aeration (subsoil ripping or keyline plowing), and erosion control (terraces, contour planting and strip cropping) may also be required. Overriding all is the logistics of food supply = providing sufficient tonnage of organic matter to feed an army of earthworms and other soil critters. This is rarely accomplished unless the soil is covered with growing plants 365 days each year.
–> A watershed management plan is recommended as more water = more vegetation = higher earthworm populations. The goal is to capture and store every drop of rain that falls upon your land. Passive or active irrigation may be needed to maintain worm populations at desired levels.
–> Reaching the goal of 2 or 3 million earthworms per acre is nearly impossible without some form of “mixed agriculture” = crops and farm animals. Animals provide manure needed to feed large numbers of worms.
–> Cow manure applied at 1 pound per square foot ~ 22 tons = 44,000 pounds per acre yearly is sufficient to maintain populations of 1 million earthworms per acre (on fields where plants are grown year-round = 365 days annually).
–> Earthworm populations soar when pastures are managed by intensive rotational grazing or mob grazing. High concentrations of livestock (300 to 1,500 Animal Units per acre per day) deposit vast quantities of manure. Fresh manure is excellent worm food. (1 Animal Unit = 1 AU = 1,000 pounds of live animal weight, regardless of species).
–> The ancient Roman practice of cattle penning relies on earthworms to help restore “tired”, “weak”, or “sick” fields. Erect temporary fencing around land to be healed. Broadcast seed or spread wildflower hay over soil. Fill enclosure with livestock until land is “well crowded” = animals have just enough room to turn around ~ 8 x 8 feet = 64 square feet per cow ~ 680 cows per acre. Feed livestock in pen until land is “well dunged and trodden” = 1/2 to 1 pound of manure per square foot ~ 10 to 20 tons of manure per acre = move livestock to new pen every day or every other day. Cattle stomp seed into earth. Earthworms and dung beetles till soil. Manure and urine fertilize ground. Pastures or fields are “enlivened” = revived by intensive dose of organic matter which causes soil critter populations to soar. Soil organisms jump start biological nutrient recycling system which supports land revegetation. Earthworms provide natural soil restoration without tractors, diesel fuel, or synthetic chemicals.
–> Greek philosophers first noted the link between earthworms and improved crop growth. This observation led to the development of worm farming practiced by cottagers and other small landholders who did not have cows or draft animals to produce manure for fertilizer. In spring spread cut weeds and other green plant materials over garden. Apply mulch thickly = 8 inches deep. This was the original green manure. In fall, rake tree leaves and spread over garden 8 inches deep. Keep garden covered with weeds and leaves year-round.
The night before planting, take a lantern and collect earthworms from hay fields or pastures. Put worms in a pail with damp moss or leaf mold to keep the “wrigglers” from drying out. Set several worms with each seed or transplant. cover immediately with soil and just enough mulch to lightly shade the soil. When plants are established tuck mulch close around their stems. Water garden as needed. Do not spade, fork, plow, till, hoe, or cultivate soil — just plant, mulch, and harvest. Continuous mulch feeds and protects earthworms and topsoil. You can run entire farms on nothing but fresh cut weeds and native earthworms. Space rows widely so there are sufficient weeds to mulch crops liberally.
–> Over a typical 5 to 6 month growing season, 1 million earthworms per acre will excrete 150 to 180 TONS of worm casts. These are deposited throughout the soil profile from the surface to approximately 6 feet deep.
Note: This is a vast amount of nutrients ~ 6.88 to 8.26 pounds of earthworm castings per square foot! Where does all the fertilizer go? There are far more available nutrients than any crop could possibly absorb. This is a mystery. Nutrient recycling must be extremely rapid with most of the fertilizer elements held within soil critters and organic matter.
–> Fertilizer Analysis of Surface Earthworm Casts Collected Nightly for 31 Days in July 2011 from 16 Organic Farms in Austria:
2.56% Nitrogen : 1.31% Phosphorous : 1.56% Potassium: 3.69% Calcium = 51.2 pounds Nitrogen + 26.2 pounds Phosphorous + 31.2 pounds Potassium + 73.8 pounds Calcium per ton of earthworm casts. Average organic matter content of earthworm casts sampled = 7.1% by dry weight. 50 casts bulked for each sample. 16 farms x 31 days = 496 samples total.
–> Average Nutrient Concentration in Earthworm Casts:
5x Nitrogen (500% more N than found in parent soil)
7x Phosphorous (700% more P than found in parent soil)
10x Potassium (1,000% more K than found in parent soil)
1.5x Calcium (150% more Ca than found in parent soil)
3x Magnesium (300% more Mg than found in parent soil)
Earthworms are living fertilizer factories. They ingest their weight in soil and organic matter daily then excrete manure containing concentrated plant nutrients. These nutrients are highly available = easily absorbed and will not “burn” plant roots. Earthworm casts are rich sources of essential plant micro-nutrients. These trace elements are often “tied up” = unavailable in parent soils but highly soluble in earthworm casts. Plants fertilized with earthworm casts rarely require additional nutrients. This is why earthworm casts have been the standard natural greenhouse fertilizer since the 17th century.
Would You Like To Know More? Contact the Author directly if you have any questions or need additional information about managing agricultural earthworm populations.
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About The Author: Mr. Koperek is a plant breeder who farms in Pennsylvania during summer and Florida during winter. (Growing 2 generations yearly speeds development of new crop varieties).