More Science

The Conversion of Organic Wastes into Vermicomposts and Vermicompost 'Teas' Which Promote Plant Growth and Suppress Pests and Diseases.
Edwards, Clive A., Norman Q. Arancon, Tse Chi Kai, and David Ellery. "The Conversion of Organic Wastes into Vermicomposts and Vermicompost ‘Teas’ Which Promote Plant Growth and Suppress Pests and Diseases."

Effect of aqueous extracts from vermicomposts on attacks by cucumber beetles (Acalymna vittatum) (Fabr.) on cucumbers and tobacco hornworm (Manduca sexta) (L.) on tomatoes
​Edwards, Clive A., Norman Q. Arancon, Marcus Vasko-Bennett, Ahmed Askar, and George Keeney. "Effect of aqueous extracts from vermicomposts on attacks by cucumber beetles (Acalymna vittatum)(Fabr.) on cucumbers and tobacco hornworm (Manduca sexta)(L.) on tomatoes."Pedobiologia 53, no. 2 (2010): 141-148.

Suppression of green peach aphid (Myzus persicae) (Sulz.), citrus mealybug (Planococcus citri) (Risso), and two spotted spider mite (Tetranychus urticae) (Koch.) attacks on tomatoes and cucumbers by aqueous extracts from vermicomposts
Edwards, Clive A., Norman Q. Arancon, Marcus Vasko-Bennett, Ahmed Askar, George Keeney, and Brandon Little. "Suppression of green peach aphid (Myzus persicae)(Sulz.), citrus mealybug (Planococcus citri)(Risso), and two spotted spider mite (Tetranychus urticae)(Koch.) attacks on tomatoes and cucumbers by aqueous extracts from vermicomposts." Crop Protection 29, no. 1 (2010): 80-93.

How does vermicomposted dairy manure protect plants from disease?_ Poster
Allison L.H. Jack(1), Eric A. Carr(1), Thomas Herlihy(2), Eric B. Nelson(1)
(1)Cornell University Department of Plant Pathology and Plant-Microbe Biology, (2) RT Solutions

Effects of humic acids from vermicomposts on plant growth
Arancon, Norman Q., Clive A. Edwards, Stephen Lee, and Robert Byrne. "Effects of humic acids from vermicomposts on plant growth." European Journal of Soil Biology 42 (2006): S65-S69.

The influence of humic acids derived from earthworm-processed organic wastes on plant growth
Atiyeh, R. M., S. Lee, C. A. Edwards, N. Q. Arancon, and J. D. Metzger. "The influence of humic acids derived from earthworm-processed organic wastes on plant growth." Bioresource Technology 84 (2002): 7-14.

Suppression of two-spotted spider mite (Tetranychus urticae), mealy bug (Pseudococcus sp) and aphid (Myzus persicae) populations and damage by vermicompostsArancon, Norman Q., Clive A. Edwards, Erdal N. Yardim, Thomas J. Oliver, Robert J. Byrne, and George Keeney. "Suppression of two-spotted spider mite (Tetranychus urticae), mealy bug (Pseudococcus sp) and aphid (Myzus persicae) populations and damage by vermicomposts." Crop Protection 26, no. 1 (2007): 29-39.

Disease-Suppressive Vermicompost Induces a Shift in Germination Mode of Pythium aphanidermatum Zoosporangia
Carr, Eric A., and Eric B. Nelson. "Disease-suppressive vermicompost induces a shift in germination mode of Pythium aphanidermatum zoosporangia." Plant Disease 98, no. 3 (2014): 361-367.

Lab results of vermicompost and worm castings

I have been curious to know exactly what the difference was between unscreened vermicompost, 1/8" screened vermicompost (what is commonly referred to as worm castings), 1/4" screened and the material that is left over after screening (I refer to those as overs because they do not fall through the screener). Over the winter of 2015 I sent 4 different samples of vermicompost to Penn State Laboratory and Earthfort Labs. The vermicompost was all taken from the same worm bed and mixed well before being screened.

Both lab results were surprising. The biggest surprise was that the nutrient levels in the overs were higher than in the 1/8" screened. I discussed this with the lab consultant from Penn State and realized why. When I screen the vermicompost two thirds of it does not go through the screener because the vermicompost is about 65% moisture; the worm castings become joined together and are too big to pass through the screener. So, therefore, the overs contain a lot of worm castings. I don't know if this is typical for other vermicompost operations they would probably have to run similar tests to know for sure.

The lab technician from Penn State also said that all results were in an extremely stable range, all were very high in nutrients, there was a nice consistent trend and that any differences were not big enough to make an impact. What the intended use is would be the deciding factor. For instance finer material for adding to seed starting and potting mixes; whereas bulkier material for mixing around plants and making vermicompost tea.

The biological analysis and a discussion with Earthfort also showed that there was hardly any real significant difference in the different samples. They all had excellent biology and the levels were practically the same within tolerance. One exception was that the unscreened had higher beneficial nematodes but the levels in the screened samples would likely recover. The deciding factor on what screen size to use would again be the intended use.

Now that I've had the different screen size samples tested I am sure that they are all high quality vermicompost. I can now confidently sell the unscreened and overs to my customers.

What is the difference between castings and vermicompost?

Once, I was asked what I cut my vermicompost with.  I was caught off guard and said I don't mix my vermicompost with anything.  But because some products are labeled as castings or vermicastings I can see how people would wonder why I label my product vermicompost and doesn't that make my product inferior. So, I have done some research from 2 of my favorite books (listed below) to explain the differences.

Technically, vermi-casts or earthworm castings are only the organic material that has passed throught the earthworm's digestive system and been excreted.

The terms vermi-cast and earthworm castings are often used to distinguish it from conventional compost. Also, in some states there are strict regulations on organic waste hauling operations. Since vermiculture and associated activities are considered an agricultural activity using the terms vermi-cast or earthworm castings can help to point out the difference in the way it was made.

In some finished vermicomposts it may be difficult or impossible to distinguish actual earthworm castings from associated organic materials (including humus) that may not have passed throught the gut of an earthworm but nonetheless have undergone physical and biochemical transformations during the vermicomposting process characteristic of advanced stabilization and humification.

In the book, Vermiculture Technology, it is suggested that the terms vermicompost, earthworm castings or vermicastings may be used interchangeably when strict, process based standards are followed to the processes leading to the accelerated stabilization and humification of organic materials at mesophilic temperatures and under aerobic conditions by ingestion, fragmentation and mixing by earthworms and microorganisms.

Some process based standards should include:
  • Mass of earthworms present in the processing material be at least 1 pound of
    earthworms for each 1/2 pound of food given per day
  • Temperature well below 113 degrees (would indicate thermophilic composting taking place)
  • Monitor moisture
  • Processing time
  • Time allowed to cure
  • How stored
  • Duration of storage
  • Vermicompost system used
  • Raw materials used
  • Preprocessing such as precomposting
  • Any amendments added

The product I sell is vermicompost, which is technically what it is. When deciding on which product to buy the important thing is how it was made. My vermicompost is made with precomposted manure and bedding from cows, pigs and a local horse farm, some wood chips and some compostable kitchen waste from our home. After it's precomposted to at least 113 degrees for at least 3 days to kill weed seeds and pathogens it is fed to the worms in amounts that they will eat over the next few days. The worms are inside, watered frequently and kept warm in the winter with heat cables that do not use a lot of electricity. After about 60 days the vermicompost is scraped off the bottom of their 4' x 8' beds. It's allowed to cure for at least 4 months then screened to 1/8" before being packaged. The lab analysis are posted on the Devine Gardens website for you to review.

I hope this information helps you make more informed decisions on which brand of vermicompost to buy.

A Work About Humus

Good vermicompost contains worm castings and humus - totally decayed organic matter. Humus is stable and complex. It can surround potentially harmful chemicals and prevent them from causing damage to plants. Humus can lessen drainage and compaction problems in clay soil and improve water retention in sandy soils. Humus has a large surface area-to-volume ratio allowing for a lot of contact with the surrounding soil. Humus has many negative charges that enable it to hold on to positively charged nutrients such as calcium, potassium and magnesium allowing them to be gradually released to plants instead of leaching away. Humus also contains humic and fulvic acids.

The above information was gathered from these really good books.

Edwards, C. A., Norman Q. Arancon, and Rhonda L. Sherman.
Vermiculture Technology: Earthworms, Organic Wastes, and Environmental Management.
Boca Raton, FL: CRC, 2011.

Magdoff, Fred, and Es Harold Van.
Building Soils for Better Crops.
Beltsville, MD: Sustainable Agriculture Network,  2009.

When you have the time watch this well done video titled Vermicompost - A Living Soil Amendment at

Below is a good study that highlights vermicompost's ability to improve seed germination.