Earthworms

“Every soil particle has been through an earthworm at least once.” – Charles Darwin

Earthworms are segmented worms that can grow from a few inches to as much as a yard in length. An acre of healthy garden soil can contain 2 to 3 billion earthworms, capable of moving 18 tons of soil a year in search of food.

Bacteria are the primary source of food for earthworms, but some earthworms feed also on fungi, nematodes, protozoa and on organic matter.  Earthworms’ wastes (or vermicasting) are 50% higher in organic matter than soil that has not moved through worms. It changes the composition of the soil, increasing Cation-exchange Capacity (CEC) because it contains a larger amount of charge-holding organic particles.

Earthworms’ digestive enzymes unlock chemical bonds that tie up nutrients that would be otherwise unavailable for plant consumption. Vermicasting is seven times richer in available Phosphate, then times in potash, five times in Nitrogen, three times in Magnesium and 1.5 times in Calcium than soil that has not been through an earthworm. They can deposit from 10 to 15 tons of castings per acre on the surface annually.

As earthworms search for food, they break down organic matter in soil, speeding up the decomposition of plant material. That allows bacteria and fungi access better to the cellulose and lignin in the organic matter, further facilitating the recycling of nutrients back to the plants. The burrows that earthworms produce while moving around improve soil’s porosity and water holding capacity.

Mechanical management of soil may have a negative impact on earthworm populations as it destroys burrows and cuts earthworms to pieces. Likewise, the salts of industrial fertilizers irritate the worms, chasing them out of the soil.

A good earthworm population is a sign of healthy soil – it tells that organic matter, bacteria, fungi, protozoa and nematodes that support earthworm populations are in place.