DemoSite HB Enviro Centre

Hawke's Bay 

Worms and soil health in agriculture

Types of Worms

Epigeic species of worms live in and feed on leaf litter buildup and manure on the top of soil. They burrow into soil itself only when required due to climatic conditions – too cold, too hot, or too dry. The worms we use for worm farming are tiger worms, which are epigeic worms. Epigeic worms tend to be small, with rapid reproduction rates and able to digest large quantities of organic matter.

Endogeic species of worms live in the soil, and burrow predominantly horizontally. They ingest organic rich soil for food, and aid in aeration, root decomposition and soil mixing.

Anecic species of worms live deeper in the soil in permanent, mostly vertical burrows. These worms come to the surface to feed on decomposing organic matter. Because of the way these worms form their burrows, they have a significant effect on the soil aeration, drainage, decomposition of organic matter and nutrient cycling in the soil.

Earthworms play an important part in maintaining healthy soil in agricultural settings. They provide 3 basic functions:

  • Waste breakdown
  • Nutrient release
  • Soil aeration

Waste Breakdown

Worms eat decaying organic matter such as leaf litter, animal manure, decaying plant roots and crop waste. Bacteria help worms digest organic matter and can do the job on their own, but they’re much slower at breaking organic matter down into bioavailable forms. As earthworms burrow in the soil, they leave behind mucus which is excreted through their skin. This mucus encourages bacterial growth which assists the worms in the breakdown of organic matter.

Nutrient release

As earthworms eat through the organic waste, they release important nutrients like Nitrogen, Phosphorus and Potassium back into the system for plants to uptake. So, a healthy earthworm population acts as a natural fertiliser for crops and pasture plants and means that over time, the whole system is sustainable – costing less in fertiliser and soil management to the farmer, and being better for the environment.

Worm casts (manure) is rich in nutrients, and worm tea (urine) is a strong fertiliser. That’s part of the appeal for people who have worm farms – they reduce organic waste and produce organic fertiliser in the process.

Soil aeration

Aeration of the soil is important in order to allow good drainage, and to improve the soil structure. The burrowing efforts of worms also allow roots to find paths in otherwise firmly compacted soil. Worm burrows allow oxygen to penetrate further into the ground, and carbon dioxide to be released more efficiently, allowing microorganisms and worms a better environment to thrive and do their good work.

Problems for Worms

Animal Drenches

Animals on farms are regularly drenched to remove or kill ‘Internal Parasites’ or worms. The worms that live in animals are different from soil worms, but they share enough common features that animal drenches can severely curtail earthworm populations. The manure from recently drenched animals will get eaten by earthworms, who then die. Given enough recently drenched animals in a paddock, a large proportion of the Epigeic and Anecic worm species can die. Populations take time to rebound to previous levels and in the meantime, they’re not providing all of the usual worm benefits. There are some new drenches which are earthworm friendly, so do your research and select safe products.

Pesticides, Herbicides and Fungicides

Pesticides sprayed onto crops to kill insects can harm earthworm populations (as well as beneficial insects like bees). Organic management is best for worms but if that’s not possible, read warning labels, MSDS sheets and make sure you know the impacts of the chemicals you’re using on non-target animals and plants. Some herbicides are toxic to worms. Fungicides, especially those containing copper or zinc, are harmful to worms.

Ploughing of soil

Ploughing of soil breaks apart earthworm burrows, alters the natural layers of the soil that the worms live and feed in and often dries out the soil beyond the level that worms can tolerate. This can dramatically affect earthworm populations in the area, reducing benefits for the next generation of crop or plants while populations recover.