Combined results from 10 samples of my vermicompost over 10 months (approx)
(a) pH 7-8.2
(b) Organic carbon 12 – 17.98%
(c) Nitrogen 1.50-2.00%
(d) Phosphorus 0.9 – 1.7 %
(e) Potassium 1.05-1.20%
(f) Calcium 0.4-0.8%
(g) Magnesium 0.3-0.6%
(h) Sulphates 0.5%
(i) Iron 0.6%
(j) Zinc 300-700 ppm*
(k) Manganese 250-740 ppm
(l) Copper 200-375 ppm
And other micro nutrients with vitamins, enzymes and hormones.
*ppm - parts per million
That might seem low compared with commercial fertilizer. However, the value of vermicompost (or worm castings) is more significant than a standard N-P-K fertilizer scale would suggest.
"Vermicompost is far more complex than chemical fertilizer, and it contains many other substances (biological and chemical that improve soil and support healthy plants. Some of these include humus, worm mucus, and plant growth promoters like cytokinins. In addition, vermicompost commonly contains ten times as much micro organism activity as plain soil (microscopic bacteria and fungi).
The micro organisms in the vermicompost are able to provide the plant with everything it needs to be healthy. Because the compost is a living system there is no excess fertilizer to run off. The humus and worm mucus in the vermicompost helps the soil hold more water, retain its structure and keeps it aerated, while also providing binding sites for micro-nutrients that would otherwise wash out of soil during heavy rains."
The nutrients content in vermicompost vary depending on the waste materials that is being used for compost preparation. If the waste materials are heterogeneous (diverse in character or content), there will be a wide range of nutrients available in the compost. If the waste materials are homogenous (all of a similar kind like pure manure.), there will be only certain nutrients that are available. The vermicompost that i use is varied with food scraps/garden waste and eggshell with cardboard as the main bedding material. No manure (in this batch) but lots of Comfrey added. Air-dried powdered comfrey leaf tissues has a NPK ratio of 1.80-0.50-5.30. compared to animal manure (below).
Dairy Cow: .25-.15-.25
If you don’t think the NPK ratio of the dried leaves from Comfrey is impressive enough, you can also make a concentrated liquid fertilizer out of comfrey with an NPK ratio of about 8-2.60-20.50! (Although you’ll want to dilute this before use.)
I use worm tea as i hope to get the best of both worlds. The debate on vermicompost as a pest and disease control is still on going but i do think it makes a big difference. The problem i have is that i have far too much fun with worms.