Reprint Article:
EARTHWORMS CAN IMPROVE SOIL FERTILITY & PROMOTE CROP PRODUCTIVITY WITHOUT RECOURSE TO AGRO-CHEMICALS
Earthworms are found in wide range of soils representing 60-80% of the total soil biomass. Significantly, the worms lead to total improvement in the quality of soil and land where they inhabit and also enhance total plant growth and crop productivity. One acre of fertile land may contain more than 50,000 earthworms of diverse species. They play major role in ‘renewing soil fertility’ by continuously burrowing, ingesting, turning, mixing, aerating and improving drainage of the soil and are regarded as ‘biological indicator of soil fertility. Even they have been introduced into reclaimed soils successfully to restoreits fertility. Earthworm activity is so prolific that, on average, 12 tonnes/ha/year soil or organic matter is ingested by this population, leading to upturning of 18 tons of soil/year and world over at this rate it may mean a 2 inch humus layer over the globe . Earthworms can contribute between 20 to 40 kg nitrogen/ha/year in soil, in addition to other mineral nutrients and plant growth regulators and increase soil fertility and plant growth by 30-200%. After Darwin published his observations in 1837 on the earthworms about how it mixed plant residues & dung with the farm soil and its grinding action in the gut to comminute soil aggregates and expose fresh soil surfaces to microbial attacks many people started studying about the role of worms in soil improvement and crop production. Worms select those parts of the soil which are rich in organic matter. This was studied and reportedby several authors since. Earthworms when present in soil inevitably work as ‘soil conditioner’ to improve its physical, chemical and biological properties and also its nutritive value for healthy plant growth. This they do by soil fragmentation and breakdown of organic matter in soil & release of nutrients, secretion of plant growth hormones, proliferation of nitrogen-fixing bacteria, increasing biological resistance in crop plants and all these worm activities contribute toimproved crop productivity. Worms swallow large amount of soil with organics (microbes, plant & animaldebris) everyday, grind them in their gizzard and digest them in their intestine with aid of enzymes. Only 5-10 percent of the chemically digested and ingested material is absorbed into the body and the rest is excreted out inthe form of fine mucus coated granular aggregates called ‘vermicastings’ which are rich in NKP (nitrates,phosphates and potash), micronutrients and beneficial soil microbes. The organic matter in the soil undergo humification’ in the worm intestine in which the large organic particles are converted into a complex amorphouscolloid containing ‘phenolic’ materials. About one-fourth of the organic matter is converted into humus. The humic acid has very good impact on plant growth. The colloidal humus acts as ‘slow release fertilizer’ in the soil.
Worms provide high levels of bio-available nutrients in balanced form for plants
Earthworms excretion(vermicastings) in soil carry ammonia, nitrates, nitrogen, phosphorus, magnesium and other micronutrients and nitrogen fixing microbes. Earthworm mix organic and inorganic, living and nonliving elements indiscriminately and smear the milieu with mucus, urine and faeces to form balanced plant nutrient. They produce ‘extra soilnutrients’ from grinding rock particles and by enhancing atmospheric nitrogen fixation. They mineralize thenitrogen (N) and phosphorus (P) in the waste to make it bio-available to plants as nutrients. They ingest nitrogen from the waste and excrete it in the mineral form as ammonium and muco-proteins. The nitrogenouswaste excreted by the nephridia of the worms is plant-available as it is mostly urea and ammonia. The ammonium in the soil is bio-transformed into nitrates. What is more significant is that it is ‘organic nitrogen’ that do not accumulate in food products in a concentration that accumulates in food grown on chemical nitrogen(urea) posing health risk.
Nitrogen (N) contribution to soil:
Barley & Jennings reported that worms significantly contribute nitrogen(N) contents to soil by over 85%. When the young growing worms were fed with a soil containing finely groundleaf litter (containing nitrogen in non-bioavailable forms for plants), about 6% of the ingested nitrogen was excreted in bio-available forms for the plants. After 28 weeks soil with living worms contained 75 ppm of nitrate nitrogen, compared with the control soil which contained 45 ppm. Patil found that earthworm recycle nitrogen in the soil in very short time and the quantity of nitrogen recycled is significant ranging from 20 to 200kg N/ha/year. Worms increase nitrogen levels in soil by adding their metabolic & excretory products (vermicast),mucus, body fluid, enzymes and decaying tissues of dead worms. They also contribute nitrogen indirectly through fragmentation of organic materials and grazing on soil microorganisms. Earthworms tissues contains about 10% N on a dry weight basis. Whalen (208) reported that living wormsrelease nitrogen from their bodies and after death it is rapidly decomposed releasing all nitrogen into the soil.Christensen found that 50% of the N in dead worm tissues was mineralized in 7 days while Satchell found it to be 70% in 10-20 days and the N was converted to NO3-N which is bio-available form onnitrogen to crop roots. The release of mineral N after death of earthworms could be significant since wormbiomass can turn over up to 3 times a year in farm soil. Study estimated direct flux of nitrogen throughearthworm biomass in farm soils (agro-ecosystems) ranging from 10-74 kg N/ha/year. Stinner, estimatedthat total N uptake by corn crops in organic and inorganic fertilized farm soils was about 90 kg N/ha/year.
Phosphorus (P) contribution to soil:
It is well established that worm casts are richer in ‘inorganic phosphoruscompounds’ extractable in water than the surface soil ingested. Graff and Sharpley & Syers found thatexchangeable phosphorus (P) measured isotopically was three times greater in worms vermicasts than in theunderlying soils.Lee suggests that the passage of organic matter through the gut of worm results in phosphorus converted to forms which are more bio-available to plants. This is done partly by worm’s gut enzyme‘ phosphatases’ and partly by the release of phosphate solubilizing microorganisms in the worm cast.
Worms stimulate high levels of beneficial and biologically active soil microbes:
Earthworms hosts millionsof beneficial microbes (including the nitrogen fixers) in their gut and excrete them in soil along with nutrientsnitrogen (N) and phosphorus (P) in their excreta i.e. vermicast. The nutrients N & P and the intestinal mucusexcreted by worms are further used by the microbes for multiplication and vigorous soil remediation and fertilityimprovement action. Teotia reported bacterial count of 32 million per gram in freshvermicast compared to 6-9 million per gram in the surrounding soil. The mycorrhizal fungi stimulated andencouraged by the earthworms transfer phosphorus by increasing solubilisation of mineral phosphate by theenzyme phosphatase. Morgan & Burrows, showed that the number of beneficial bacteria and‘actinomycetes’ contained in the ingested material increased up to 1000 fold while passing through the gut. A population of worms numbering about 15,000 will in turn foster a microbial population in billions in soil.
Worms secrete plant growth hormones: Neilson reported the presence of ‘plant growth substances’ inearthworms. Tomati had also reported that worm worked soil & compost contained growthpromoting hormone ‘auxins’ and flowering hormone ‘gibberlins’ secreted by earthworms.
Worms protects plants against various pests and diseases: There has been considerable evidence in recentyears regarding the ability of worms to protect plants against various pests and diseases either by suppressing orrepelling them or by inducing biological resistance in plants to fight them or by killing them through pesticidalaction. The actinomycetes fungus excreted by the earthworms in their vermicast produce chemicals that killparasitic fungi such as Pythium and Fusarium.
VERMIWASH: THE NUTRITIVE LIQUID FILTERED THROUGH BODY OF WORMS PROMOTE GROWTH AND WORKS AS ORGANIC PESTICIDES
The brownish-red liquid which collects in all vermculture practices should be collected. This liquid partiallycomes from the body of earthworms (as worm’s body contain plenty of water) and is rich in amino acids,vitamins, nutrients like nitrogen, potassium, magnesium, zinc, calcium, iron and copper and some growthhormones like ‘auxins’, ‘cytokinins’. It also contains plenty of nitrogen fixing and phosphate solubilisingbacteria (nitrosomonas, nitrobacter and actinomycetes).Farmers from Bihar in North India reported growth promoting and pesticidal properties of this liquid. Theyused it on brinjal and tomato with excellent results. The plants were healthy and bore bigger fruits with uniqueshine over it. Spray of vermiwash effectively controlled all incidences of pests and diseases, significantlyreduced the use of chemical pesticides and insecticides on vegetable crops and the products were significantlydifferent from others with high market value. These farmers are using vermicompost and vermiwash in all theircrops since last 4 years completely giving up the use of chemical fertilizers & pesticides. (PersonalCommunication With Farmers in India).
VERMICULTURE: A GLOBAL MOVEMENT
The movement was started in the middle of 20th century and the first serious experiments for management of municipal/industrial organic wastes were established in Holland in 1970 and subsequently in England andCanada. Later vermiculture were followed in USA, Italy, Philippines, Thailand, China, Korea, Japan, Brazil,France, Australia and Israel. However, the farmers all over the world have been using worms forcomposting their farm waste and improving farm soil fertility since long time. In UK, large 1000 mt vermi-composting plants have been erected in Wales. The American EarthwormTechnology Company started a 'vermi-composting farm' in 1978-79 with 500 t/month of vermicompostproduction. Hartenstein & Bisesi reported on the management of sewage sludge and effluentsfrom intensively housed livestock by vermiculture in USA. Japan imported 3000 mt of earthworms from theUSA during the period 1985-87 for cellulose waste degradation. The Aoka Sangyo Co. Ltd., has three 1000t/month plants processing waste from paper pulp and the food industry. This produces 400 ton of vermicompost and 10 ton of live earthworms per month. The Toyhira Seiden Kogyo Co. of Japan is using rice straw, municipal sludge, sawdust and paper waste for vermicomposting involving 20 plants which in totalproduces 2-3 thousands tons of vermicompost per month (72). In Italy, vermiculture is used to biodegrademunicipal and paper mill sludge. Aerobic and anaerobic sludge are mixed and aerated for more than 15 days andin 5000 cum of sludge 5 kg of earthworms are added. In about 8 months the hazardous sludge is converted intonutritive vermicompost. In France, 20 tons of mixed household wastes are being vermi-composted everydayusing 1000 to 2000 million red tiger worms (Elsenia andrei) in earthworm tanks. (205). Rideau RegionalHospital in Ontario, Canada, vermi-compost 375-400 kg of wet organics mainly food waste everyday. The wormfeed is prepared by mixing shredded newspaper with the food waste. In Wilson, North Carolina, U.S., morethan 5 tons of pig manure (excreta) is being vermi-composted every week. In New Zealand, Envirofert is alarge vermicomposting company operating in over 70 acre site in Auckland converting thousands of tons of green organic waste every year into high quality compost (www.envirofert.co.nz).Vermiculture is being practiced and propagated on large scale in Australia too as a part of the 'UrbanAgriculture Development Program' (to convert all the municipal urban wastes into compost for local foodproduction) and ‘Diverting Waste from Landfills Program’ (for reducing landfills in Australia).
CONCLUSIONS AND REMARKS
Earthworms act as ‘Ecosystem Engineer’ converting a product of ‘negative’ economic & environmentalvalue i.e. ‘waste’ into a product of ‘highly positive’ economic & environmental values i.e. ‘highly nutritive organic fertilizer’ (brown gold) and ‘safe food’ (green gold). Vermiculture can maintain the global ‘humansustainability cycle’-producing food back from food & farm wastes. Earthworms and its metabolic products (vermicompost) may work as the ‘driving force’ in sustainable foodproduction while improving soil health and fertility and protecting crop plants from pests and diseases. They cancompletely ‘replace’ the use of agrochemicals in crop production. This is what is being termed as ‘sustainableagriculture’. .
Tribute to the earthworms:
Earthworms are justifying the beliefs and fulfilling the dreams of the great visionary scientist Sir Charles Darwin as ‘unheralded soldiers’ of mankind and ‘friend of farmer’s. Darwin wrote a book in which he emphasized that ‘there may not be any other creature in world that has played so important a role in the history of life on earth’
One of the leading authorities on earthworms and vermiculture studies Dr. Anatoly Igonin of Russia has said: ‘Nobody and nothing can be compared with earthworms and their positive influence on the whole living Nature. They create soil and everything that lives in it. They are the most numerous animals on Earth and the main creatures converting all organic matter into soil humus providing soil’s fertility and biosphere’s functions:disinfecting, neutralizing, protective and productive’