Vermicompost Experiments Update

Hi Everyone,
Just wanted to provide a super quick update on the vermcompost growth experiment front. As you may recall, I set up a couple of preliminary trials (see “Vermicompost Growth Experiments“) about a week and a half ago just to get the ball rolling.

Some pretty interesting results already, I must say! As you can see in the picture above, the Chia seeds have started sprouting and one of them clearly has a LOT more plants coming up. Surprisingly enough, it is actually the potting-soil-only treatment! Of the two vermicompost treatments, the one without the rock dust (one on left) seems to be doing better so far – while there seems to be a similar number of seedlings, leaf size on average seems to be larger in the no-rock-dust mix.

I am happy to report that my two sad looking marigolds have bounced back from their near-death experience (haha), but nothing too earth-shattering to report in general. It’s too early to say for sure, but once again the rock dust vermicompost treatment may be impeding growth a bit. The marigold in that treatment (middle one in the picture) doesn’t look as full and healthy as the vermicompost-only (left plant) and the potting-soil-only (far right plant).

Very important not to reach ANY conclusions about any of this. For one thing I want this to be an ongoing experiment – I’m really interested to see what happens over the long-haul. Also, it’s once again important to realize that there is only one rep per treatment so not exactly rigorous scientific work here!

I DID decide to start up what I’d consider to be a much more scientific trial today though. I am testing the growth of radish plants from seed. Similar to these other experiments, I am looking at potting-soil-only, 33% vermicompost + soil, and 33% special vermicompost (with rock dust and some grounds) mix + soil.

I am using a 6-cell seedling holder for each treatment so we may actually be able to do some real comparisons here.

Will keep everyone posted!

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  1. If these plants are in the same order as the prior photo, then I’m definitely impressed with the VC only. It looks like it jumped way ahead of just the potting soil. Wow.

  2. For seed starting and for immature plants a low-nutrient medium is best. The weaker the mix, the better. As the plant grows, so do their nutrition needs.

    A very nutrient-rich medium (such as and especially vermicompost), used right from the start, tends to work in an undesirable way, sometimes even turns out to be fatal.

    I predict the potting-soil only will prove to work best. I may be wrong.

    • Bentley
    • June 21, 2011

    PATRICK – Yep, same order. The VC/Soil mix does seem to have more buds and to be as least as bushy as the soil-only, but we’ll see how things progress from here.
    PERMABLOGGER – Interesting info – thanks for sharing that. I really wanted to do a vermicompost-only treatment (ie 100% vermicompost), but alas, I didn’t have another one of the 6-cell mini planters. Would have been very interesting to see what would have happened to the seedlings in that one.
    What’s funny is you can have all sorts of different seedlings pop up in vermicompost (when you don’t necessarily want them to – haha).
    Anyway – should be fun to see how things pan out.

    • Anna
    • June 22, 2011

    Bentley–What are the ingredients in the Pro-Mix used? Does it include fertilizer?

    Permablogger–I’m interested in your assertion. I’ve just heard the opposite–that it’s better to add a little nutrition at the outset rather than try to add later.

    • Laura
    • June 22, 2011

    Comments from what I’ve observed: Certain plants (corn, bean, squash and gourd plants, for example) thrive in compost-rich soil. If they have too many nutrients, they may look lush but not produce much.Other plants (tomatoes) need a somewhat lower level of nutrients in the soil to be at their peak production. Tomatoes (and apparently chia plants?) actually get burned/ poor looking if the nitrate levels are too high.

    Question: How can you keep the trays cool enough yet in a sunny location to grow radishes at this time of year?

  3. The Strawberry Store uses VC to start strawberry plants. Bentley also linked to some seed starting and growing research (I can’t find it now 🙁 ) that shows different results depending upon variety and VC concentration. Seeds don’t really need fertilizer to get started, I agree. I don’t think that worm castings are “too much” though. The NPK varies but is never very high. I just found a reference that indicates a value of 3.2-1.1-1.5 – which seems kinda high based upon other references. The fact that you can start seeds in VC tells me that it shouldn’t really burn your plants. Try starting some seeds in straight Miracle Grow and see what you get….

    • Bentley
    • June 23, 2011

    Interesting discussion!
    ANNA – Good question. My assumption is that yes, there would be some starter fertilizer, but I will have to take a close look at the bag to find out for sure.
    LAURA – Squash definitely DO seem to thrive in association with my vermicomposting beds. I’ve had pretty good success with tomatoes as well though, but perhaps it’s because I don’t actually add any other fertilizer.
    I wonder how high is “too high” for nitrates? Vermicomposting definitely leads to increased nitrate levels.

    As for keeping the trays cool, your guess is as good as mine! haha
    This is why it’s better that I am not a super-pro gardener. I just do dumb things without any worry about what will and won’t work. I probably wouldn’t have done half the things I’ve done out in the garden (vermi-trenches etc etc etc) if I knew any better! lol

    Anyway, I guess we shall see! (but I will definitely take the info to heart and make sure the radish trays stay in the coolest location possible)
    PATRICK – I am not 100% sure which research you are referring to, but here are a couple of excellent academic research pages: (Cornell) (Ohio State University)

  4. Bentely,
    I’m not sure if those were the links or not. I”m pretty sure I followed them from here. I want to say the most effective balance was about 20% castings to other planting medium. It was an interesting read to be sure.

  5. Hi Patrick,
    The research you are referring to was almost certainly conducted by the team at OSU. It may be listed on the OSU page above (and perhaps I linked directly to the document from a post).

    This is something I definitely want to write more about, and I’ll be sure to track down some more academic results.

    • Laura
    • June 23, 2011

    Bentley and Patrick–I actually haven’t experimented with vermicompost and tomatoes yet. (Instead, I gave it to the squash and cucumber plants, which are thriving.) I just assumed they wouldn’t do well together since I know in previous years when the tomatoes got fertilized with somewhat aged manure (chicken/goat) they did poorly or even died. They do best for me when they are just in an area that had something else growing (say beans) last year and were fertilized then. Maybe vermicompost is gentler, and certainly I’m sure it depends on the type of soil you have. If you started with very poor soil I guess you’d want to fertilize almost anything you’d grow.

  6. Here is an interesting one from that page:

    Here is an interesting snippet from the abstract:

    “Substitutions with all of the vermicomposts into MM360 increased germination signi?cantly on almost all sampling dates”


    • Anna
    • June 23, 2011

    I should’ve added my source yesterday when I posted. It was Dick Zondag, the owner of Jung’s seed catalog who said that you need to start with an enriched growing medium. Here’s a link to the whole conversation (approx. 75 minutes) which covers a range of topics:

  7. I no longer use ProMix because it has a non organic wetting agent but, yes, it does have an initial fertilizer charge. It has just enough to get plants started.

    Another point is that vermicompost has components that promote germination and growth like humates. Don’t just look at the N-P-K only. The other components along with the organisms (if the vc is not as dry as dust) are equally, if not more important, than the N-P-K.

    My experience is that 100% vc has a “toxic” effect on seedlings and plants. I found the best range to be 10% to 40% VC to soiless mix (I now use SunGro Organic Mix)


    • Bentley
    • June 25, 2011

    Well said, Mike!
    I totally agree (and what you’ve found yourself seems to closely mirror the consensus from the OSU research group).
    For fun I am going to set up some experiments using deep-frozen (then thawed) vermicompost, bone dry vermicompost, and regular stuff just to see how they compare in terms of performance.
    Should be interesting!

  8. Works good if you have a big bin like mine to start seeds in the bin.I’m testing an heirloom tomato i just threw in there and gave a squeeze.Was waiting to see if the hybrids somehow would cross and either the hybrids may start growing.Or the heirlooms wouldn’t grow because they cross pollinate.The top couple inches is just about the perfect starter mix it appears in what i find.But i’m no green thumb! I just know worm bins are like nature,in that the top is not all worm castings.Probably the perfect ratio in a lot of cases!JMO

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