I can't say much about the difference in the product, but I do see some advantages to the process. A worm bin can be very small and the worms process the material relatively quickly. For a compost pile to work quickly it has to get hot and to get hot it has to be fairly large. People who live in apartments or for other reasons do not have a large area for composting can do very well with vermicomposting.

MKitten, I'm not debating the process or if it's good or bad. I think the size factor is the biggest plus when it comes to worms. I'm considering setting up a worm bin myself. I've read in different places about how good the worm castings are, and I was wondering about what makes it better!

Well, I don't have the knowledge of Kelly, but I don't think vermicompost is really that much BETTER than compost. Just different. I use both.

Marianne, if I've not mentioned how refreshing I find your common sense, please allow me to do so now. You're a gem!

Whip, I don't think your question sounds the least bit argumentative! Rather, it is an excellent question the anwer to which needs to be repeated over and over to as many people as possible; worm castings are NOT better than compost and should not be described as such. They are, in fact, very different than compost, thus comparing the two is akin to arguing that a toothbrush is better than a spoon. Earthworm castings are not produced through the same process as compost, but are generated through an internal process that combines enzymatic and anaerobic digestion, while compost is produced through largely aerobic microbial decomposition. The resulting chemistry in the two materials is very different (based on research conducted by Dr. Rola Atiyeh of Ohio State U) as are much of their physical characteristics. When generated from the same feedstocks, for instance, castings contain concentrations of compounds that duplicate plant growth hormones and regulators while these compounds are either missing in the compost or present at much lower concentrations. Salt concentrations, however, are also higher in castings than in compost generated from the same feedstock, meaning castings should be used at lower concentrations than compost to prevent problems with salt toxicity.

Another reason to avoid making value judgements between compost and castings is because value is predicated upon the intended end use of any product. If one needs, for instance, to get as much OM into their soil as possible, castings are unlikely to be a good choice since the high salt content makes it unwise to apply them at concentrations typically suitable to increasd overall OM. Compost would tend to be the better choice for this application. If one is looking for the stimulation provided by the chemistry associated with castings, however, well, then castings are obviously the better choice. The yardstick for measuring value needs to be consistent before one can say that one thing is better than another.

Most important to understand is that the greatest level of overall plant benefit is demonstrated when compost and castings are applied to the soil together. A blend of compost/castings typically demonstrates generally improved plant performance in multiple areas (root growth; fruiting/flowering; drought tolerance; and, anecdotally, insect and disease resistance) better than does either compost or castings alone.

I am also frustrated with the continued claim that castings are "rich in nutrients", as this is a very misleading statement. While castings do TEND to contain more macronutrient than does compost, neither contain sufficient concentrations of soluble nutrient to compare favorably with fertilizer or raw manure. I've even heard is said that castings are the "richest natural fertilizer known to man", which is a load of BS. In fact, real bull shite, or cow shite, or pig shite, or chicken shite, or bat guano, or human sewage is much richer in nutrient than is either compost or castings, and they are most certainly "natural fertilizers"! Now please understand, I am most definitely NOT saying fertilizer or raw manure are better than compost or castings, I am saying they contain more soluble nutrients. We must remember, however, that there is far more to promoting plant growth than simple NPK. Many university plant growth trials have proven, in fact, that plants grown in media that includes compost/castings tends to germinate faster and at higher percentages, set true leaves earlier, produce more fruit and blooms, produce more root mass, and tolerate drought and disease better than do plants grown in media not containing compost castings even when all plants in the trial are fed and watered with the same optimized feeding and watering schedule. This demonstrates that the value of compost/castings goes well beyond simple nutient and water retention responses.

In truth, Whip, there is not much research directly comparing compost and castings, and what there is does not prove that one is universally better than another. Further, and to directly respond to one of your questions, researchers don't know with certainty all the chemicals and characteristics associated with castings that are most broadly responsible for their beneficial impact on plant vitality. They, like we average gardeners and farmers, simply know that the stuff is good.

When you read on web sites that castings are better than compost, take it with a grain of salt. Such value judgements do a disservice to gardeners and usually indicate a lack of understanding of plant and soils needs on the part of the person making the judgement. Between compost and castings, it's all good!

Kelly S