A Chemical Analysis of Worm Castings
November 12th, 2008
I’ve always been curious about the content of worm castings. I have seen and experienced anecdotal evidence that the castings I pull from the bottom of my bin are extremely good for the plants to which I apply it.
There are a number of pages with the mineral content of worm castings, including this one, this one and this one, but I wanted to know what my own castings contained. I don’t doubt that the contents of your bin are going to depend on what you put in it. For example, I’d expect eggshells in the feedstock to increase the calcium content, and crushing those eggshells would probably increase that further.
I decided to contact my local soil testing lab and see what their analysis found. I dug a worm castings from the bottom of my bin and sifted them to remove any large chunks of wood and undecomposed material. I let them dry for a night, placed them in a labeled plastic bag, and filled out a form specifying tests I wanted. I mailed the whole package off to the lab.
Six weeks later, after a phone call to remind the lab I was waiting for results, I received the analysis. Here are the comments from the soil lab:
pH, which was 7.9, was “sufficient for a soil amendment.” Most plants have a pH range they prefer.
Electrical conductivity or salts: “The salts are elevated, however this material can be safely used as a soil amendment if it is used at the recommended application rates.” They didn’t give me recommended application rates, however.
Lime estimate: low, which “indicates less than 1% CaCO3.”
Sodium adsorption ratio (SAR): “Low; sodium is not a problem.”
Everything else tested had “high” levels, including O.M. (Organic Matter), NO3-N (Nitrate-Nitrogen), P (Available Phosphorus), K (Available Potassium), Zn (Available Zinc), Fe (Available Iron), Mn (Available Manganese), and Cu (Available Copper).
Numbers (ppm) and such available in the Full Worm Casting Analysis Report.
Entry Filed under: Uncategorized
5 Comments Add your own
1. shailesh | March 4th, 2009 at 6:09 pm
how to estimate cation exchange capacity of vermicompost
2. vermicomposting | March 4th, 2009 at 6:14 pm
Hi shailesh,
I’m not sure how you would do this, given that home vermicompost varies in composition widely.
Via this link: http://www.wormdigest.org/content/view/371/2/
I found this paper that you may want to try to read for methods:
Harada, Y. and A. Inoko. 1980. The measurement of the cation exchange capacity of compost for the estimation of the degree of maturity. Soil Sd. Plant Nutr., 26:127-134.
Hope this helps.
3. AKHILESH VIJAY | September 8th, 2009 at 4:12 am
seems very intresting to know abt this type of work. I am very much intrested to know more abt it.
4. vermicomposting | September 8th, 2009 at 7:15 am
Hi Akhilesh Vijay,
Welcome! There’s a lot to learn about worm castings and their properties. But theres’s also a lot of information out on the web. I suggest starting at wikipedia and exploring from there, always with a skeptical eye.
5. Myco-vermicomposting arti&hellip | October 26th, 2009 at 8:15 am
[...] can turn nutrients into different, more accessible forms, but, as I mention in my post about sending my worm castings to a soil lab, the chemical contents of your bin depend on what you put into it. Earthworms aren’t [...]
Leave a Comment
Some HTML allowed:
<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>
Trackback this post | Subscribe to the comments via RSS Feed