It really comes down to a number of factors pertaining to how both products were manufactured. If the same source material was used in both (lets say cow manure for arguments sake) and you follow protocols that are recognized to be best standard practice for the manufacture of both thermophyllic composts and vermicomposts respectively, then you will end up with two products that are similar in terms of nutrient availability, dissolved Carbon and microbial abundance. However your functional microbial diversity will be different for the two products (Biolog Ecoplates are useful in determining this) this may result in a different suite of secondary metabolites being formed which may effect the plant community differently. This is an aspect of  the comparison between compost and vermicompost that has not yet been investigated, to my knowledge. There are several papers out there that have compared thermophillic composts with vermicomposts and I'll attach them below, but no authors (to my knowledge) have yet investigated the difference in nutrient cycling rates and profiles attributed to the microbes within these two different organic ammendments. What the authors tend to agree on though is that a combination treatment of pre-composting and then vermicomposting results in a product that is of superior quality in terms of stability as well as N, P and C content. From my own research I have also found that pre-composting reduces the time required to achieve a stable vermicompost. From the literature it seems that vermicomposts produce a greater variety of phytohormones while compost contains slightly greater amounts of mineral nutrients, this is presumably due to reduced leaching during the composting process compared to vermicomposting. However both amendments yield similar growth responses across a variety of crops, when similar source materials are used. That being said, I suspect that soil type and plant community assemblage will play a role in how these two amendments influence crop yields.

I hope this helps. Typically though, there is no simple answer.

Dear Hue

Vermi-compost has its own merits and limitations. Worms do not prefer harder materials. Therefore at larger scale thermo-compost can be considered as better option. Quality wise there is not much differences between the two types of composts. 

Dear Hue,

I agree with the view given by Karbassi, however, the quality of compost material depends on the ingredients used. If same materials is used  to make compost by  both the methods, nutrients contents wise much differences may not be there but organic substances may vary. These organic substances help in soil aggregation and improvement of soil quality? 

The vermicompost as compared to thermocompost, has an additive effect since partially decomposed plant litter essentially soft and succulent ones, pass through the digestive tract of earthworms that enables digestive juices and mucus of earthworms to mix up with excrement which is termed as vermicompost. Whereas, this process does not occur in case of thermocompost which is produced by aerobic and anaerobic decomposition processes over crop residues and other materials of plant and animal origin. To evaluate comparative merits of these two, is to conduct incubation studies in a microbiology laboratory to find quantity and diversity of microbes. The composts are essentially intended to feed soil sheltered organisms but not to supply nutrients directly to crops. Let us understand this basic object of application of composts. Soil fertilization is crucial to soil quality. as it serves as a basic foundation to support higher plants. 

Althought compost quality greatly depends on initial organic materials, in general terms vermicomposts have smaller particle size as a consequece of worms feeding. The passage of a material throughtout worm gut increase microbial biomass and activity in a greater extent as compared to composting. In addition, it has been demostrated that worm activity promotes a humification of organic material  more intensely than composting. However, these are only general assumptions reported from the mayority of studies, and more studies focused on comparing the effect of thermal-compost vs vermicompost on soil and crops are still demanded.

It really comes down to a number of factors pertaining to how both products were manufactured. If the same source material was used in both (lets say cow manure for arguments sake) and you follow protocols that are recognized to be best standard practice for the manufacture of both thermophyllic composts and vermicomposts respectively, then you will end up with two products that are similar in terms of nutrient availability, dissolved Carbon and microbial abundance. However your functional microbial diversity will be different for the two products (Biolog Ecoplates are useful in determining this) this may result in a different suite of secondary metabolites being formed which may effect the plant community differently. This is an aspect of  the comparison between compost and vermicompost that has not yet been investigated, to my knowledge. There are several papers out there that have compared thermophillic composts with vermicomposts and I'll attach them below, but no authors (to my knowledge) have yet investigated the difference in nutrient cycling rates and profiles attributed to the microbes within these two different organic ammendments. What the authors tend to agree on though is that a combination treatment of pre-composting and then vermicomposting results in a product that is of superior quality in terms of stability as well as N, P and C content. From my own research I have also found that pre-composting reduces the time required to achieve a stable vermicompost. From the literature it seems that vermicomposts produce a greater variety of phytohormones while compost contains slightly greater amounts of mineral nutrients, this is presumably due to reduced leaching during the composting process compared to vermicomposting. However both amendments yield similar growth responses across a variety of crops, when similar source materials are used. That being said, I suspect that soil type and plant community assemblage will play a role in how these two amendments influence crop yields.

I hope this helps. Typically though, there is no simple answer.

Nice post by Ricky! I agree, the funtional microbial diversity is a key element besides plant nutrient content. 

Cornell University has done extensive testing of vermiculture products for agricultural crops. I agree with Ricki Allardice on all points and find that the enzymatic response in vermicompost is dramatically higher. Microbial activity and population is higher. Actual processing time is shorter and uses fewer mechanical inputs.  Its a different set of products than compost. The worm "juice" from the bins can has as much as 1250 ppm N and 5400 ppm K. A liquid product. Then the castings or compost, the worms, and worm eggs. All have a benefit in the soil when applied appropriately.

Articles:

Influence of earthworm culture.pdf

Properties in Earthworm Cast.pdf

I agee with Daniel. But I would like to remind us that vermicomposting is more expensive than composting if it is considered that more water is usually needed to prepare organic waste for worms. A optimal vermicomposting process requieres near 80-60% humidity. 

On the other hand, I would like to clarify that worm are normally removed from end vermicomposted product, and used for a new vermicomposting  process of as a source of animal protein. Consequenly, vermicomposts doesn't often contain worms when those organic products are applied as soil amendments.

Does anyone know paper in which compost or vermicompost produced from the same organic material were used as soil amendment, comparing their effect on soil fertility?  

Manuel,

I've attached a paper that should answer your question. The authors compared composing and vermicomposting of municipal biosolids as well as backyard vermicomposting. They found that vermicompost contained higher mineral nutrients, increased microbial populations and activity in the soil and increased rye grass biomass when compared to thermophyllic compost. The authors do also state though that comparisons cannot be drawn across the board, since source material plays such a key role.  However other authors have found composts to contain more mineral nutrients than vermicompost. I think it is safe to say though that vermicomposts contain a greater abundance and diversity of microbial life than thermophillic composts. 

Daniel,

I agree that leachate derived from vermicomposts is rich in mineral nutrients, however it is also anaerobic, providing a good breeding ground for many plant pathogens. If this can be overcome through aeration perhaps then this resource can be utilized more effectively? Leachate is also very rich in dissolved carbon and humic/fulvic acids. Currently this is an aspect of vermicompost research that has been largely ignored but definitely warrants further attention because if you combine the potential benefits to plant production of leachate and vermicompost you may well have a product that is highly competitive with chemical fertilizers. What do you guys think?