I'm very skeptical that anyone sells pure worm castings. I define a casting as a particle that has actually passed through the digestive tract of a worm. Vermicompost or worm compost is a much more accurate description of what is probably in the bag.

Your homegrown VC is probably different from stuff you buy for a number of reasons. I can't remember which forum this came from, but it was posted by: Kelly Slocum On: 2001-09-01.

"the feedstocks chosen for producing maximum worm biomass are not always those chosen to produce the best castings for a particular situation, no.

keep in mind that castings value is determined largely by the intended end use. if you want the castings to amend your soil for planting a fruit orchard, for instance, the castings you'd most want would be dominated by microscopic fungi, supported in castings produced by a feedstock with a high proportion of carbon material (leaves, wood, paper, cardboard, etc.). were you looking for castings with which to amend soil that will be growing annual flowers the product with the highest value to you would be dominated by bacteria. bacterial castings are produced with feedstocks higher in nitrogen (greenwastes, manures, etc.). castings that have the most generally diverse community of organisms possible are generated from feedstocks with a particular balance of carbon and nitrogen bearing materials.

now, studies show that, provided appropriate moisture and aeration are maintained, manure is the material that produces the greatest worm biomass. manure alone is not going to produce castings with the most diverse numbe of organisms, however, needed for a high qualtiy general purpose product."

Note the tacit implication that NPK is not what makes VC a valuable soil amendment. Search "soil food web" and you'll have plenty of reading material.

Cheers,
Andrew

My first worm bin effort is nearing completion of its first "cycle," ie. all the original bedding is mostly gone and unrecognizable and it pretty much "finished." I have periodically for the last 4 months fed them about 1 lb (probably a little less) of rotten cow manure. This near finished product still has some small pieces of leaves and paper (the original bedding) in it. Since it's not purely castings, I consider it to be vermicompost. This end product is very fluffy and light. WHen I stir it with my hands, it sticks very little to my fingers. There's probably 30 lbs of the stuff and I can't wait to put it to use, regardless of what it is called.