Vermicompost Comparison-07-26-12

I figured it was about time I posted an update on my cucumber-growing (with vermicompost) experiment. If you happened to miss the first installment, here is the link: “A Tale of Three Vermicomposts“. I’m actually quite surprised I still have any of my plants left, to be totally honest. Apart from dealing with seedling-munching chipmunk early on (I kid you not), I’ve also been battling with very hot, dry weather (by our standards, anyway). Speaking of which, I actually did end up giving up on the small passion-flower seed growing experiment since it was just too difficult to keep the three small pots moist.

The results of the other two experiments have been quite interesting so far. I am definitely seeing some strong evidence to indicate that not all vermicomposts are created equal! Before I elaborate, let me quickly point out that the following results should IN NO WAY serve as a reflection of the quality of the vermicomposting system these vermicomposts were created in. There are MANY different factors that can play a role in helping to create a top notch vermicompost, such as the type of feedstock, frequency of feeding, quantity of worms present in the system etc. Obviously the type of bin/bed used will still be an important factor – I just don’t want people assuming these types of systems are no good for producing decent vermicompost simply based on my results. I’ll definitely discuss this a bit more once I’ve shared the results.

A quick word or two about the chipmunk munching (lol) before we dive in here. The seedlings in the larger (100% vermicompost, with one black earth control) pots were not harmed at all, but in the soil + vermicompost experiment I ended up with only two seedlings in the WF-360 treatment and two seedlings in the manure-vermicompost treatment (the other two treatments were unharmed). Since this entire project is mostly for fun, I don’t think I’ll lose any sleep over it. lol

OK – the “results”…

For starters, it seems as though my own hunch about 100% vermicompost potting mixes not being the best choice has some validity. I guess you could say this is based on more than a “hunch”, though, since it mirrors some of the findings in the academic literature. Of the three vermicomposts, the manure vermicompost appears to be the “best” in terms of supporting plant growth on its own, and may be even better than the black earth soil as you can see in the first image below.

The WF-360 and Worm Inn vermicomposts did not fare quite so well. The plants growing in the WF-360 vermicompost actually ended up getting killed off by some sort of disease (seemed to be some form of “damping off”). The Worm Inn vermicompost plants survived, but as you can see below they seem to be suffering from some sort of deficiency (likely low nitrogen).

Based on the look of the plants in the soil + vermicompost experiment (below), I think it’s safe to say that including vermicompost as part of a potting mix (with soil etc) is likely a better strategy! Interestingly enough, the plants seem to be more robust in all the treatments with vermicompost than in the black-earth-only control pots. That being said, there IS still some evidence to suggest that the Worm Inn and WF-360 vermicomposts contain some compounds (or disease organisms) that are negatively affecting plant growth. Some of the leaves in these treatments appear to be stunted and/or to have some blemishes on them.

In all honesty, the results (so far) really don’t surprise me all that much when I think back to how the WF-360 and Worm Inn systems were managed prior to harvesting the vermicompost! Both systems were badly neglected, and the resultant vermicompost in both was likely derived largely from the processing of shredded cardboard – rather than lots of rich food wastes.

According to various research studies conducted at Ohio State University (the “Mecca” of academic research in this field) manure vermicomposts have always tended to perform better than those created from other materials, so I’m also not TOO surprised to see this one outperforming the others (especially considering how the other ones were made).

What I’d like to do now is transfer the soil + vermicompost plants to larger pots (with more of the same mix they are in), and add some slow-release fertilizer tablets to each of them to see how they respond. One of the important findings in the academic literature has been the fact that vermicomposts appear to provide plant-growth-promoting benefits that go above and beyond simple fertilization, so it will be interesting to see if the plants in the vermicompost treatments continue to outperform those in the black earth soil.

I’d like to get to the point of actually growing cucumbers if I can, since it will be even more interesting to see if the presence of my vermicomposts helps to improve yields at all.

Should be fun. Stay tuned!

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    • John
    • July 26, 2012

    I have to say…looking at that first pic with the border line dead looking plant in the WF 360 is kind of depressing since that is the system I use. I use a lot of cardboard so I can only hope mine comes out better than yours! 🙂

    • Bentley
    • July 26, 2012

    Like I said, John – please do NOT take these results to heart! There are any number of factors that could have lead to this. If you use the system the way it’s supposed to be used I’m sure you will end up with nice stuff.

    • GA
    • July 28, 2012

    I think it’s also worth pointing out here that quality, true ‘black earth’ may not be the best comparison – in that you’re really comparing with a fantastic growing medium for most types of plants. (It may be a fair comparison for many growers if that’s all they’re using, but it’s also – for most – a fairly expensive option).

    Hard to come up with a fair soil control group, as every place will differ, but true black earth is really going to be close to incredibly old, aged worm castings where everything has stabilized perfectly into true humus.

    Or to summarize differently: worm compost is likely best used as a soil amendment, something to add to soils with low organic content or poor microbial activity, and not as a ‘soil substitute.’

    I also forget your original post and maybe you did this, but suspect what seems to be the pathogen/disease/fungus issues affecting the plants might be addressed in part by letting the worm compost sit out in dry sun and air for a good long while.

    I also wonder – from personal experience – whether the issues with using worm compost directly are much more severe in potted plants (as opposed to a garden bed). Just seems any organism imbalances in potted plants would have a tendency to get out of hand much more quickly in an enclosed environment.

    • Julie
    • July 30, 2012

    Great experiment and very educational! I really appreciate the comments added by other people as well. This is a fascinating webste!

    • Bentley
    • July 30, 2012

    GA – Thanks for sharing your thoughts!

    I think it’s safe to say that my “Black Earth” is not “true black earth” – it’s just the brand name of the bagged potting soil I’m using. It still looks decent, and seems to support plant growth fairly well, but my hunch is that they actually create the stuff rather than digging it from a real black earth source. (And, it’s also not very expensive stuff at all)

    I agree 100% with your assertion that vermicompost is best used as an amendment, NOT as a soil substitute, which is why I set up the small side experiment testing growth in 100% vermicompost. Although, I don’t necessarily think the soil needs to have low organic matter. Vermicompost has unique properties/compounds/microbes not necessarily found in other rich soils/composts.

    You are likely right about the WF-360 vermicompost requiring either a longer curing period, or better yet, a more effective curing process. Just tossing the material into a bin with air holes and leaving it down in my basement for months likely wasn’t the best solution! haha
    I wouldn’t ever leave vermicompost in hot, direct sunlight, but some place outdoors with some better air flow and warmer temps (than a basement) likely would have been better.

    I also agree re: effects of disease organisms on a potted plant vs one sitting in the garden. I can pretty much guarantee that all plants would have done very well (in comparison) had they been planted in an actual garden since various other stress factors wouldn’t likely have been as significant.
    JULIE – thanks for the kinds words.

    • GA
    • July 30, 2012

    Thanks Bentley and enjoying the site and experiments.

    One point of clarity: didn’t mean to imply that soil used with vermicompost “needs to have low organic content.” Rather, my point was that the additional impact of vermicompost (other composts too) would be most noticeable where it was being added to poorer-quality soil. And that the positive impact might be a lot less noticeable for very high quality organic soil like (true) black earth, maybe even marginal in some cases.

    Maybe my idea of leaving it in the sun was overdoing it, but another approach might be to add to the other soil, mix, and let it sit for a while and stabilize in a natural environment, probably a somewhat dry one. Wouldn’t work with my own planting and projects, where I tend to dig a hole and throw a bunch of compost in and just plant right away. (So far with good results but I’m not testing anything)

    But if people using fresh worm compost are noting issues, it could easily be just a bit too much young compost.

    Like I said, I tend not to worry about it too much, and if the easiest solution for me is to plant directly in vermicompost, I’ll just do that ))

    Thanks again!

    • Bentley
    • August 2, 2012

    OK – gotcha, GA!
    Once again, you’ve made lots of good points.

    One of my most memorable experiences involving the “magic” of vermicompost (and really, my FIRST experience with using some of my own) involved simply digging a bunch of black stuff from the bottom of an active worm bin and dumping it in a pot I was moving a tropical plant into. The growth of that plant in the new pot with the vermicompost absolutely EXPLODED! So I agree – the “no worries” approach isn’t necessarily “bad” that’s for sure.

    There are so many factors that can affect the “quality” of this stuff, and even just how it get’s used makes a big difference. This is definitely why I don’t want people to take the results of this particular experiment too seriously.

    Thanks again for sharing your thoughts!

    • Mads
    • August 7, 2012

    Hi Bentley,

    I’ve been with you here since November 2011 where I also started my first Rubbermaid bin. I’m completely hooked on worms and by now I’ve expanded to three bins and have big plans about taking it to a commercial level.
    I’ve harvested a couple of times and in both cases the bottom of the bins were quite soggy, in one case even smelly. When it comes to Rubbermaid vermicomposting this seems to be the rule rather than the exception, but I’ve found a solution for this:
    After the initial turbo-light harvesting I put the wet vermicompost in a bin with air holes and then stick sheets of cardboard in it. After a couple of days these sheets of cardboard have drawn a lot of liquid out of the vermicompost and it’s easy to shred them for bedding in another box. I put in new sheets and if the vermicompost is still to wet after a week or so I repeat a third time (haven’t been necesarry yet). This sponge-method works really well: The excess liquid is transferred from compost to cardboard and the worms that weren’t separated while harvesting will happily munch on the cardboard. The soft cardboard is filled with microbial life and makes excellent bedding or can be used for homemade manure when setting up new bins.
    I’m making short videos of my life as a vermicomposter and will soon make one on this very issue. My previous videos can be seen here:

    They are in Danish, so probably you and most of your readers won’t understand much, haha.

    Thanks for a great site and lots of inspiration!

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