Why Worm Castings?

What Are Worm Castings?

Worm castings are the excrement (or poop) worms produce after ingesting organic matter. They are also referred to as "vermicast," "vermicompost," and "black gold."

Worm castings are distinct from traditional thermophilic compost. Though both processes begin with organic waste, worm composting is performed at lower temperatures and the waste passes through the microbially-rich lining of the worm's digestive tract. This results in a product that contains a greater diversity and abundance of microbes, as well as higher nitrogen levels.

Notably, worm castings have a neutral pH (6.5-7.0) and can be applied immediately to plants without the need for curing or fear it will burn plant roots. It has an earthy smell and should not stink.

Most worm castings contain a small amount of bedding or uneaten material. Due to this, producers run their castings through a 1/8" sieve to ensure a more consistent product without worms, worm cocoons, or visible feed stock. Some will also brew their worm castings to make a "compost tea" that can be used when watering.

Benefits for Soil

Soil it seems has entered the mainstream--discussed for its impact on the environment's health, its ability to sequester CO₂, and its importance in promoting food security. Growers know that healthy plants and tasty fruits and vegetables begin with healthy soil. Here's how worm castings can contribute to your soil profile:

• Add organic matter

• Increase soil porosity and aeration

• Reduce bulk density of heavy soils

• Decrease water loss and nutrient leaching

• Form stable aggregates that help reduce erosion

• Increase cation exchange capacity, which increases the availability of calcium, magnesium and potassium

• Buffer soil pH

• Add beneficial soil microbes

Benefits for Plants

We all want our plants to grow big and luscious. Worm castings are one soil additive that can help you achieve this goal. Packed full of microbes and essential nutrients, worm castings can give your plants a big advantage. Here's s how they help:

• Provide nutrients including nitrates, potassium, phosphorous, calcium, and magnesium

• Contain plant-growth hormones, including auxins and gibberellins

• Contain humic and fulvic acid which make insoluble minerals plant-available

• Increase root growth and plant biomass

• Speed up germination of seeds and increase seedling growth

• Reduce transplant shock

• Reduce pests, including aphids, cucumber beetles, white caterpillars, two-spotted spider mites, tobacco hornworms, and fruit borers

• Suppress plant diseases including Pythium, Verticillium, Phomopsis, and Rhizoctonia

• Decreases the amount of parasitic nematodes by attracting beneficial arthropods and fungi

*Note the exact composition and effect of worm castings can differ greatly between producers. Worm castings do not benefit all plant species equally and have varied effects on different types of pests and plant diseases. Do your research before you make a purchase. Before buying bulk amounts, it can help to buy a small amount and test its specific effects.

MORE RESOURCES

Adhikary, Sujit. "Vermicompost, the story of organic gold: A review." (2012).

Blouin, Manuel, et al. "Vermicompost significantly affects plant growth. A meta-analysis." (2019): 1-15.

Edwards, Clive A., Norman Q. Arancon, and Scott Greytak. "Effects of vermicompost teas on plant growth and disease." Biocycle 47.5 (2006): 28.

Pathma, Jayakumar, and Natarajan Sakthivel. “Microbial diversity of vermicompost bacteria that exhibit useful agricultural traits and waste management potential.” SpringerPlus vol. 1 26. 4 Oct. 2012, doi:10.1186/2193-1801-1-26

Sherman, Rhonda. "The Worm Farrmer's Handbook: Mid- to Large-Scale Vermicomposting for Farms, Businesses, Municipalities, Schools, and Institutions" (2018)