Back in antiquity, Aristotle called them the “intestines of the Earth,” but it took several more centuries before earthworms were systematically studied — by Charles Darwin who wrote a whole book on the importance of worms in breaking down dead organic matter, enhancing soil structure, and maintaining soil aeration, drainage and fertility. Darwin calculated that earthworms in the soil add about eleven tonnes of organic matter per acre (about 18 tonnes per hectare) each year; modern scientists believe that where worms abound they can move up to 250 tonnes per hectare per year.

According to Darwin, earthworms have an acid reaction in the upper part of their digestive canal which affects the soil and organic matter passing through the canal. Calciferous glands in their gut secrete carbonates of lime, which slowly neutralise the acidic particles and eventually change the reaction to alkaline as the transiting soil reaches the lower part of the digestive canal. As earthworms feed, the carbon-to-nitrogen ratio in organic matter progressively declines. Nitrogen is converted into more usable ammonium or nitrate forms; phosphorus, potassium and other nutrients are also converted into readily available forms.

As various kinds of mineral and organic particles pass through the earthworm digestive canal, they get mixed very close together to form aggregates, which improve the drainage and moisture-carrying capacity of the soil. These organic matter-mineral aggregates have great water stability and enhance other characteristics of the soil. Various investigators believe that as much as 50% of aggregates found in surface layers of the soil come from earthworms.

In addition to aggregates, earthworms also play very important roles in forming soils, improving soil structure and enhancing its physical characteristics. Modern agriculture utilises earthworm products in various ways.

Worm composting

Also called ‘vermiculture,’ the term refers to the production of humus from organic matter by using a combination of microorganisms and earthworms. Unlike other composting processes, worm composting does not require heat to degrade and stabilize organic material; instead, it makes use of intimate interactions between the earthworms and the microbes that live in their intestinal tract and in the organic material. Worm composting yields two economically valuable products — vermi-cast and vermi-meal.

Earthworm casts consist of remains of digested organic matter, mucous and nitrogen-derived substances. The texture of these casts is finer than can be found in traditionally composted wastes. Vermi-cast is superior to inorganic fertilisers in its ability to provide growth nutrients. Apart from the normal N-P-K (nitrogen, phosphorus and potassium) contents, vermi-cast delivers enzymes, beneficial microbes, and growth hormones. Vermi-meal is a protein-rich meal made from ground earthworm meat. Its protein content is about 62% with 11% fat. It can be used as an ingredient for animal feeds.

Worm juice

Worm juice is a special product from earthworms. It also contains some N-P-K, but its major benefit comes from its plentiful supply of nitrogen-fixing bacteria (about 100,000 CFU/ml), trace elements, and minerals all mixed in an aerated liquid and immediately available to the plant. Usually applied at the rate of 10 litres per hectare, worm juice helps the soil regain its natural capacity to provide plants with the nutrients they need in readily available form. It is also used as a foliar spray and as dressing on seed coats to increase germination rates.

Worm compost tea

Also known simply as ‘worm tea,’ this nutrient solution is a liquefied form of vermi-cast produced from worm composting, further enriched with minerals, essential plant nutrients, and all the various microorganisms so necessary to soil health and enhanced plant growth. Application is easy but it is important that worm tea be applied within 4 hours after the solution is activated. Worm tea is usually applied on the soil, plant leaves, and mulch to promote soil health.

Continued use of earthworms and earthworm products will help you eliminate inorganic fertilisers and other chemicals in your farm.