What’s in the Worm Juice?

A couple of weeks ago I mentioned that I would be taking a look at the leachate that comes from vermicompost. Here is the worm house, owned by Master Gardener Meleah Maynard, from which this leachate came. This is a picture from when the house was new — it now has multiple floors.

It has been running for a few years now, and the “ingredients” that she puts in, mostly table scraps, are pretty typical of what anyone would put into compost. She reports that it produces about a gallon of leachate every 2-3 weeks. The leachate from this house has the following properties:

  • pH – 8.5: That’s a high pH for soil, but for a fertilizer added every week or two it’s fine.
  • Nitrogen – 1120 ppm: That’s high for a fertilizer.  About twice the concentration I’d use if I were applying a liquid fertilizer to my plants at home. The nitrogen is present mostly as nitrate, which is a good thing.  If the nitrogen were present primarily as ammonium, that might cause problems.
  • Phosphorus – 22 ppm: That’s a good/appropriate concentration of phosphorus for most plants. It’s much less than we apply when we use a typical garden fertilizer. Potassium – 5034 ppm: This is an order of magnitude higher than we’d apply for most plants using a liquid fertilizer.
  • Calcium – 279 ppm: This is a reasonable amount of calcium.
  • Magnesium – 211 ppm: This is reasonable amount of magnesium.
  • Sodium – 634 ppm: I’d like to see less sodium, but this shouldn’t cause a major problem.
  • Other elements present included Iron, Copper, Manganese, Zinc, Molybdenum, and Boron, all at levels less than 1 ppm.

So what’s my conclusion? I think that, based on the nutrients and nothing else (no trials), this could be a great liquid fertilizer if it were used properly. I’d recommend diluting it somewhere between 1:1 and 1:5 worm juice : water before applying it, and I’d only apply it once every week or two. If you want to use it, try it on something that you’re not too concerned about first, just to make sure that it doesn’t do anything too terrible (It shouldn’t, but I believe in caution).

27 thoughts on “What’s in the Worm Juice?”

  1. I’ve often wondered about my worm water mineral content and assumed that mine would vary from someone else’s based on the things I feed the worms. For instance, worms at Chez Bell have a diet high in banana peels, the tough ends of asparagus, dead flowers, withered kale, onion skins, citrus peel, and canceled checks. How much do ingredients determine the mineral output? Or more to my point, do all the things we’d generally put in a worm bin have a similar enough chemical makeup that using a lot more of one thing than the other won’t significantly alter the usefulness of the juice-fertilizer or the castings? Is there a way to adjust the contents & perhaps lower the potassium without also lowering minerals which are present in reasonable proportion?

    I’ve always diluted my worm juice since killing a patch of chamomile by using the high-octane stuff (that was my assessment anyway).

  2. Hi Laura, I’m certain that the ingredients you use do determine the output — at least to some extent. I don’t know how much. If you have the chance, send a sample to your local extension people and have them run a test on it — and then let me know what’s in there! I’ll be sure to post!

  3. I have been watering my vegetable transplants once a week or so with my work juice and I love it! I dilute about 3 cups in a large watering can. It really seems to wake my transplants up and get them going! Maybe it’s all the coffee grounds the worms get? 🙂

  4. Please define worm juice. It is NOT the liquid drained from the bin as in a recent MG article. Compost tea is what I apply to my indoor plants. I adjust the PH to 7.0 or less, higher can “burn” citrus loving plants.

  5. Hi Joan,

    Actually, it is the liquid drained from the bin. Do you have the MG article? I’d like to take a look at it.

  6. Worm juice producers should know that even though these are reasonable levels of nutrients, that doesn’t mean your landscape soil is devoid of them. Adding additional nutrients to landscapes that don’t need them can cause all kinds of toxicity problems for plants, soils, and whatever is downstream.
    I’ve said it before and I’ll say it again – do soil tests first before adding any fertilizer, organic or otherwise, to your landscape.

  7. Any idea why the pH is so high? That’s already a problem in our area due to hard water. I find it a little surprising, but wonder if her choice of substrate has anything to do with it. N content is pretty startling, too.

  8. This is really interesting! Thanks for posting this. A gallon of worm juice every two weeks. That’s a lot of organic fertilizer, stored up by the end of the winter… Good for the yard in the spring, once the ground thaws. But a bear to carry out of the basement, without sloshing. I couldn’t use it all on my houseplants during the winter months. Thanks, also to Meleah, for sharing!

  9. This will probably vary from bin to bin depending on what the worms are fed. In the UK we generally recoment 10:1 dilution with water and I use it on everything – my tomatoes love the stuff. It is also a great way of adding not only nutrients but microorganisms back into tired soil.

  10. Can you tell us more about how to test these things? It would be a fun thing for us to do in our school garden and compare with your results.

  11. Hi Grace, there are lots of ways to test, but I think a florists test is probably the cheapest and easiest. Just ask your University soils lab.

  12. Hi Jeff,
    You can use the liquid drained from your worm bin. As for me I would not put that “smelly” stuff on my house plants. i will continue to make compost tea and correct the PH.

  13. I would never use any liquid magic mixture in garden soils ever, but i think it would serve better purposes on Potted plants where material building up in the pot would be a challenge. Otherwise I prefer using Earthworm castings under shrubs and letting the natural forces gradually break things down for plants to utilize. for example these casting have worked great for me in the past under Hibiscus to discourage large White Fly infestations which can overwhelm them in Southern California. Beyond that teas have never interested me.

  14. Liquid from my worm bin is awesome. I have used it on my houseplants and it is NOT smelly. I am now adding the liquid worm juice to outdoor trees and plants. My veggies are organic or without pesticides. I hope to add the worm liquid to my lawn. I have 2 compost bins, one is outside and I have one inside. It snows here so being able to discard my veggie refuse during the winter is great.

  15. Hi Jeff,
    I’ve been collecting the worm juice in a bin which sits under the worm bin where my worms reside. I just poured the liquid into gallon jars, after collecting it for several months. How long will this juice keep, does it lose it’s beneficial properties, or go “bad”? Can I store the gallons jars of worm juice in the refrigerator, and then use them in a diluted form for my seed starts?
    Thank you for your advice,

  16. will aerating the concentrated leachate change any of the ingredients
    for example the nitrogen component?
    the ph?
    the concentration that should be used

  17. Hi Jeff,
    How did you get the analysis of the macro and micro nutrients from the worm leachate?
    I would also be interested in what other components are in leachate like potentially harmful products from anaerobic processes like ammonia or alcohols. Do you have any of that kind of information?


  18. Hello,
    I was just wondering how many worms would be in this vermicomposter and how many people were using it? Thanks!

  19. I haven’t purchased Fetilizer for years. I have several 55 drums that I use. Each drum has several PVC pipes with drilled holes for air set in vertically. Each drum has a drilled fitting near the bottom to drain liquid the liquid. The top of the barrel has a screen. Rain enters the top Worm juice comes out the bottom. I add a bag of spent coffee grounds one per week until the barrel is full (the grounds come for coffee bars). When a barrel is full I start another. I remove the first foot of Coffee and worms for the new barrel. The remainder of the barrel goes into Garden.

  20. I built my own vermi bin. I use the juice I harvest on everything from tomatoes to pot. I have been using it (I eyeball the amounts) about 1-2 cups or so of vermi juice, a dash of fish emulsion, a spade of chicken S*#% to a 3 or 4 gallon bucket, add water to the brim from a hose, aerating the mixture, mix and serve asap. Dont drench the plants with this mixture, but give them a nice dose.at the respective root perimeter and then water as usual for penetration. Repeat every 2 or 3 days. I can only speak for my own results, but lets just say NOBODY has nicer tomatoes than I do…. uck uck,


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