Why are Earthworms Important for Soil Fertility and Sustaining Agriculture?

NOTE:  This information about earthworms and earthworm castings is for general educational information purposes only.  It does not imply that our BWCN Worm Farm Premium Earthworm Castings product contains the ingredients listed below.  Our Premium Earthworm Castings product is labeled simply as a soil amendment.  

Earthworms play an important role in the creation of healthy, productive, "living" soils.  Basically, earthworm feeding and burrowing activities incorporate organic residues and amendements into the soil, enhancing decomposition, humus formation, nutrient cycling, and soil structure development.  Earthworm burrows persist as macropores which provide low resistance channels for root growth, water infiltration, and gas exhcange.¹

The major benefits can be summarized into the following three major categories:

Biological:  The earthworm is essential to composting.  They feed on organic matter and convert it into rich humus, a medium vital to the growth of healthy plants.  This is achieved by the worm's actions of pulling down below, any organic matter deposited on the soil surface (e.g., leaves, manure, etc.) either for food or when it needs to plug its burrow.  Once in the burrow, the worm will shred the leaf and partially digest it, then deposit their castings.  Worm castings contain high concentration of organic material, silt, clay and is rich in many soil nutrients such as nitrogen, sulphur, potash, phosphorus, calcium, magnesium, etc.  Worm castings are also rich in growth hormones, vitamins and act as a powerful biocide against disease and nematodes.²  A study found that earthworms in apple orchards can be an important mechanism for preventing outbreaks of scab fungus.³

Chemical:  The earthworm also ingests other soil particles that are small enough into its "crop" wherein minute fragments of grit grind everything into a fine paste which is then digested into the stomach.  When the worm excretes this in the form of castings, a perfectly balanced selection of minerals and plant nutrients is made available in an accessible form.  Investigations in the US show that fresh earthworm castings are 5 times richer in available nitrogen, 7 times richer in available phosphates, and 11 times richer in available potash than the surrounding upper 6 inches of soil.⁴  Other studies also suppor the importance of the earthworm:

• Earthworms in a pasture soil produce castings that contain 73 percent of the nitrogen found in the ingested litter, including both the importance of earthworms in incorporating litter nitrogen into the soil.⁵
• Earthworms increase the amount of nitrogen mineralized from organic matter in soil.⁶
• Nitrogen-fixing bacteria are ofund in the gut of earthworms and in the earthworm castings, and higher nitrogenase activity, meaning greater rates of N-fixation, are found in castings when copared with soil.⁷
• Earthworms can acumlate certain heavy metals, industrial effluents, arious biocides, pesticides, and their residues.⁸

These studies explain why it pays the farmer or gardener to keep worm populations high.  Click here for more information regarding Earthworm Castings Benefits.

Physical:  As earthworms burrow through the soil, they leave behind tunnels that open up passageways for air and water, thus, creating a multitude of channels which allow the processes of both aeration and drainage to occur.  The soil becomes loose, porous, and unsurpassed in fertility.  Permaculture co-founder Bill Mollison stated that by sliding in their tunnels, earthworms "act as an innumerable army of pistons pumping air in and out of the soils on a 24-hour cycle (more raidly at night).⁹  It was also found that earthworms like the Nightcrawler, "can burrow through compacted soil and penetrate plough pans, creating channels for drainage, aeration, and root growth."¹⁰

Several studies ahve reported the overall benefits of the earthwormand its role in sustaining agriculture.  That is, that these incredible earthworms are a vital component in the living biosystem that is healthy "living" soil.  These studies found that the introduction of earthworms to area not previously populated has led to improvements of soil quality and productity in New Zealand grassland¹¹; on drained Dutch polders¹²; in heathland in Ireland¹³; and in mining spoils in the US.¹⁴

The African Nightcrawler earthworms are excellent for revitalizing the soil and sustaining agriculture.  For the last two decades, the African Nightcrawler has played a major role in solid waste management in Southeast Asian nations, including be a major character of vermicomposting in the Philippines.

References

1.  Warner, Matthew R., 1990 "Earthworm Ecology and Sustaining Agriculture," University of California, Sustainable Agriculture Research and Education, Components,Vol. 1, No. 4

2.  Harender, Raj, and M.L. Bhardwaj.  "Earthworms' Role in Soil Biology."

3.  Raw, F.  1962.  "Studies of Earthworm Populations in Orchards."  Leaf Burial in Apple Orchards.  Ann. Appl Biol. 50:389-404.

4.  Wikipedia(R) Encyclepedia, Wikinedia Foundation, Inc. Earthworms.

5.  Syers, K.K. A.N. Sharpley & D. R. Keeney.  1979.  "Cycling of Nitrogen by Surface-Casting Earthworms in A Pasture Ecosystem."  Soil Biol. Biochem.  11:181-185.

6.  Ruz jerez, E., P.R. Ball and R.W. Tillman.  1988.  "The Role of Earthworms in Nitrogen Release from Herbage Residures."  In:  Jenkinson, D.S. and K.A. Smith (eds.).  Nitrogen Efficiency in Agricultural Soils (publisher unknown) pp. 355-370.

7.  Simek. M. and V. Pizl.  1989.  "The Effect of Earthworms (Lumbricidae) on Nitrogenase Soil."  Biol. Fert. Soils 7:370-373.

8.  harender, Raj, and M.L. Bhardwaj.  "Earthworms' Role in Soil Biology."

9.  Permaculture - A Designer's Manual.  1988.  Tagari Press.

10.  Joschko, M., H. Diestel and O. Larink.  1989.  "Assessment of Earthworm Burrowing Efficiency in Compacted Soil with a combinaton of Morphological and Soil Physical Measurements."  Biol. Fert. Soils 8:191-196.

11.  Martin, N.A.  1977.  "Guide to the Lumbricid Earthworms of New Zealand Pastures."  New Zealand J. Exp. Agric. 5:301-309.

12.  Van Rhee, J.A.  1977.  "A Study of the Effect of EArthworms on Orchard Productivity."  Pedobiologia 17:107-114.

13.  Curry, J.P. and T. Bolger.  1984.  "Growth, Reproduction and Litter and Soil Consumption by Lumbricus Terrestris in Reclaimed Peat." Soil Biol. Biochem. 16:253-257.

14.  Vimmerstedt, J.P. & J.H. Finney.  1973.  "Impact of Earthworm Introduction on Litter Burial and Nutrient Distribution in Ohio Stripmine Spoil Banks."  Soil Sci.  Soc Am. Proc. 37:388-391.