What Is Vermicasting?

Vermicast is the casting of earthworms. Earthworm casting is what farmers are really looking for when they are taking a spade and digging a hole in their paddock to find out about plant roots, soil structure, and soil humus. But it is easier to find earthworms than it is their casting in soils. We all know that soils with hundreds of earthworms are fertile, healthy, and sustainable soils. But why are earthworms so important for high yielding, healthy plants and food, safe groundwater, and even for ‘clean’ air? Why are earthworms so important to our soils? 

As earthworms are working their way through the top soil they mix humus and mineral particles. They are turning our soils into a sponge-like structure with enormous numbers of small, medium, and slightly larger borrows and pores. This worm created ‘sponge’ stores water, nutrients and air for the plants and other microorganisms to grow. Scientist call this the rhizosphere, where water, nutrient, and air are exchanged between plant roots, microorganism, fungi, clay minerals, groundwater, and the atmosphere. 

Besides their ‘soil tillage’ capability, earthworms produce a lot of high nutritious casting continuously while feeding. They feed on dead plant material like leaves, roots and manure from our farm animals with all the bacteria and fungi which are decomposing the organic matter. Earthworms have a crop and gizzard just like birds where the mix of food is ground down to very small fractions. Bacteria and antibiotics in the worms’ intestinal tract destroy pathogens, introduce enzymes (which makes the nutrients plant available), produce plant growth promotors, and much more. By now earthworms have created a valuable mix of nutrients, humus, enzymes, plant hormones, bacteria, and fungi during an intestinal passage of only 5 cm. Before the mix is excreted, the ‘casting’ is finally coated with a mucus so it becomes a strong humus-soil aggregate. 

Beneficial and biological active soil microorganism. 

Application of vermicast stimulates various beneficial and active soil organism in the soils. Of relevance for crop and fruit production are phosphorous solubilising bacteria, nitrogen-fixing bacteria (Azotobacter, Rhizobium, Nitrobacter) and actinomycetes and mycorrhizal fungi. 

Plant growth hormones research has shown that use of vermicast stimulates plant growth further, even when plants are already receiving ‘optimal nutrition’. Notable scientists have found plant growth promoting hormone in earthworm castings, these ‘hormones’ improves seed germination, seedling development and growth, and increases plant production and yields. In a way these hormones are ‘telling’ plants that there are plenty of worms and high-quality humus waiting for them and the plant responds with more and deeper roots and more flowers and fruits. 

Plant protector Beneficial microorganisms. 

Vermicast produces antibiotic compounds, actinomycetes and other metabolites that contribute to disease suppression. The mechanism of biological control by antibiotic compounds are effective in controlling various plant pathogens, a process known as antibiosis. Vermicast application decreases arthropods populations (aphids, mealy bugs, spider mites, buds, cabbage white caterpillar) and subsequently reduces plant damage. Farmers from Canada report reductions of several insect pests, which is explained in a production of the enzyme ‘chitinase’ that breaks down the chitin in insects’ exoskeleton. 

Disease suppressing effects on radish, grapes, tomatoes, strawberries, and peppers have been found by scientists. The disease suppressing effect disappears after sterilisation of vermicast giving evidence that the ‘microbial antagonism’ in the vermicast was the biological mechanism for the disease suppression.

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