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In Situ Worm Composting

Updated: Nov 13, 2020

Serious Business Teaching Modern Farmer Publisher Frank Giustra about the Green Resource Value of Worm Poop

I first heard learned about 'in situ', (Latin for on-site on in-place) worm communities several years ago in relation to fruit orchards where farmers utilized a combination of in-orchard and in-ground vermiculture (cultivating/farming of worms) and vermicomposting (utilizing worms to break down compost, usually for castings fertilizer) and to manage orchard waste and fertilize fruit trees with worm castings (poop) and broken down organics. As I continued my studies, about permaculture in particular, the subjects came up more regularly in relation to market gardens and small farms.

The idea of in-situ worm composting is completely adaptable and portable, and I've since incorporated an abbreviated form of it into many raised and ground-level beds in our urban permaculture garden. As in all aspects of 'urban' or 'suburban' permaculture, it is necessary to bend, re-imagine or adapt fundamental permaculture ideals around an existing and most-often non-ideal, or at least non-conforming situation.

Dave loves eating juicy worms and crunchy bugs so I keep a weighted lid on the in-ground worm compost behind him

In many neighborhoods and most residential buildings, composting is either not permitted under community or strata regulations, or is simply cause for neighborhood revolt. In such situations, vermicomposting, in particular in-ground vermi-composting can save the day. Worm composts, when managed properly are neither smelly or offensive, and they shouldn't attract the attention of unwanted pests.

I am not referring to the stand-alone, above ground worm composts that one can buy at garden centres and online, or the sort one can make from a lidded Rubbermaid container, though those are magnificent options for people without any outdoor space at all. Rather, I am referring to the creation and management of small below-ground worm communities that live in your garden bed or large container even, providing:

  • food and refuge for thousands of compost worms

  • ideal composting of green kitchen waste, and some garden waste

  • nature's best all-natural, high-nutrient fertilizer for the plants in your bed

  • aeration of the soil in your garden bed

  • a fun and educational family activity and responsibility

A black plastic in-situ worm compost is exposed after harvesting radishes, but typically the composts go un-noticed

When people visit my garden, the in-situ composts, the herb spiral, and the mini fruit orchard are the most popular features, but it is the in-ground composts hidden among the growing things that inspire immediate action frequently, to some degree. This of course makes me very happy, because the primary reason for my mid-life left turn into (urban) permaculture design was to inspire others to take action and make small changes. In situ vermicomposting is easy to get started. You will need:

  • a dark, moist (not wet), stable environment that stays cool like dirt and doesn't freeze

  • several access/egress (entry/exit) points and a weighted lid

  • a balanced, steady diet of appropriate organics

  • shredded paper bedding (preferably unbleached brown paper or leaves)

  • regular check-ins to ensure worms are happy and healthy

  • compost worms commonly known as red wrigglers (Eisenia foetida or Lumbricus rubellus) are ideal, though regular garden variety worms work also

Compost worms are available at many garden centres and online from vermiculturists. Many communities that have recycling programs also offer compost worms and compost bins (not the in-ground sort), for sale. Certainly local garden clubs would know sources, or refer you to someone who does.

I wouldn't typically compost viable tomatoes but these guys were badly munched by a resident racoon. Plenty to share.

In-site worm composts are small, typically one to 10 gallons in volume, which is very small compared to standard open composts. For that reason, I have one in-situ compost in each raised bed in the garden, plus a few in ground-level beds.

Each compost is drilled with about 100 1/4" holes spaced evenly along all vertical sides to within no less than 2" of the top lid ridge, and is sunk up to lid level in soil. Keeping the holes well below soil level, and the lid firmly in-place but not snapped shut, keeps contents from attracting wildlife, and odours inside where they belong.

I don't have issues with stinkiness, at least nothing worse than what a pile of old grass would offer (and then only when the compost lid is off), but I am also careful to compost only raw greens and other organics.

Compost worms surface quickly to investigate the addition of partially decomposed brown paper pot pieces

Fill your worm compost only with:

  • raw vegetables (except alliums) and fruit - my mix is about 80/20 respectively

  • egg shells

  • coffee grounds - I add only 20% of household grounds (the rest in garden waste bags)

  • shredded brown grocery bags, newspaper in a pinch, or brown paper plant pots

  • refuse from garden cleaning (dead soft leaves, flowers, etc)

I never add meat, dairy, oils, cooked vegetables (unless only lightly steamed), bones, citrus, onion or garlic or their skins, hard leaves, branch bits, or hard organics of any kind. Conventional wisdom says that compost worms don't like alliums like cooking onions and garlic, so I don't add them to my composts. Having said that, the worm composts in my beds containing leeks, onions and garlic are very active, and all areas within the beds themselves are impressively wormy, so I suppose my guys are fine with alliums. I haven't run out of non-alium compost feed and am happy to divert my onion and garlic skin to the regular yard trimmings bag, but if I couldn't do either of those things, I would experiment with small amount of garlic and onion and see what happens.

The point of all of this is poop, worm poop, or castings as they are known. Worm poop is gold, and worm poop tea is liquid gold. By incorporating worm composts in situ, we create an instant and constant supply of both. Since I use only organic compost as a planting medium in my beds, and my ground-level beds are blessed by well-aerated humusy soil, the exchange of materials into and out of the compost is easy and the worms do their own housekeeping simply by eating, pooping and wandering around. Uncomplicated transit in and out keeps the level of compost to a more-or-less constant and manageable level as the compost breaks down and the liquid and small particles move out into the bed soil, aided by the worms and insects that come and go. The worms deposit poop in their homes and also throughout the beds as they wander around garden partying here and there. If I had hard soil or plenty of clay in the soil, I would expect to have to empty the compost on occasion, or otherwise manage the quantity of inputs.

Worms are said to be shy, but mine are friendly and curious, surfacing whenever something new is planted

My worms are very curious creatures, and turn up in numbers without fail whenever I am planting seedlings or otherwise managing the garden. I swear they know me and like my quiet company. They are especially fond of my very young neighbours who visit regularly to check on 'their' carrots and radishes (even now, under row cover), and harvest anything they can reach, wash and munch on before heading back over the fence. Children love worms, and they love feeding them, so worm composts in-situ or freestanding are awesome projects to undertake at home, at school, even in the neighborhood.

My worm composts homes were intended for the tiny red wrigglers primarily (Eisenia foetida), the original starter batch (quart yogurt bucket full of inhabited vermicompost) gifted to me by my master gardener neighbour Yvonne. Those original wrigglers were descendants of the mail-order batch Yvonne and her young boys introduced into their indoor vermicompost bin over 20 years ago. Well-fed compost worms reproduce prolifically and quickly. I put all of the initial gift of wrigglers into just one of my in-ground composts, and as they multiplied I moved handfuls of inhabited compost into the other beds. I see very many garden variety worms and several of the larger Lumbricus rubellus wrigglers in my beds also, which means the composts are providing happy worm habitat and that word is getting around.

Installing buckets at the bed building stage isn't essential

Worm composts are easy to make with readily available plastic buckets, and can be installed immediately in a patio planter, large container, or garden bed. I wouldn't go any smaller than a one-gallon size bucket, which would suffice for a large planter or small bed, and I wouldn't go any larger than 10 gallons or two five-gallon buckets in a 4'x'8' bed. In use a single five-gallon black plastic bucket with lid in the centre of each of my 4'x8' beds.

This ratio is based on nothing other than intuition and the bulk price I was able to negotiate for the buckets, but it seems to work just perfectly. I sized my composts when building the beds, but it isn't necessary. You can easily sink buckets into existing beds.

You will need:

  • a lidded plastic bucket that can be sunk into your container of bed more-or-less completely, leaving just the lid rim and the lid exposed. Recycled food buckets are perfect, just be sure they re clean and grease-free before using.

  • a drill and a 1/4" drill bit

  • an inch or two of green kitchen scraps (see list above), and shredded paper

  • red wriggler worms (or garden worms if that is all you have)

  • a garden bed or large container full of soil

A few easy steps:

Drill 1/4" holes all around and through the bottom
  • measure two inches down from the lowest lid-rim ring on the bucket, and then drill 1/4" holes straight through the bucket horizontally, spaced two or three inches apart from each other, all the way around the circumference of the bucket.

  • do the same thing every three inches or so down the length of the bucket, alternating holes in a diamond-like pattern as you go. Drill a half-dozen, nicely spaced holes in the bottom.

  • sink the drilled bucket into your bed or container, up to the level of the lid, but making sure it is on firm enough soil that it won't sink when full.

  • add an inch or two of damp shredded paper or newspaper, sprinkle over some chopped kitchen greens, crushed egg shell and a tiny bit of coffee grounds or spent tea, to start. Small bits are best, at least in the beginning, though to be honest, I prefer uniform pieces to share among my worm families so I chop my dense and fibrous scraps up regularly.

  • another shallow layer of damp paper.

  • keep the lid on with a rock or garden tool

  • add greens and paper regularly in more or less equal measure, and water only lightly (don't drown the worms), turning occasionally with a small garden fork or tongs, and be sure there is air space throughout.

  • composts slow down in winter, and worms can freeze, so adjust feeding accordingly for your area and by observing worm activity. In cold locations, cover contents with a thick layer of fallen (non-glossy) leaves for insulation.

When I feel that I have overloaded on greens, I add some of the soil from the garden bed, and mix that in with some paper, just to lighten things up and make sure my little buddies can breathe and do their thing. They can live happily for up to 12 months, before they too become compost in situ. Such is the cycle of life.

worms need kitchen greens, brown paper and moisture

Worms will eat one to two times their body weight per week, so if you purchase one pound of worms, you can expect them to eat up to two pounds of compost per week. This ratio will vary over time, with temperature, and at different times of year, because as compost evolves and develops its own biodiversity, microbes and other visitors will consume the organics as well. This is an awesome form of pre-digestion for the worms, and it makes nutrients available to plants and fungi.

I overheard my little neighbour Sophia ask her dad how the worms in the composts poop, and he told her, through their tails.

I'm not sure if he actually knew that or if it was a guess, but it's true that a worm's bum is at the far pointy end of its 'tail'.

So now that you have the scoop on poop ... happy vermicomposting!

To learn more about the relationship between worm composting and our permaculture garden visit previous blog post No Dig Beds, and The Dirt On Soil.

To watch the Modern Farmer | Million Gardens Movement video "In Situ Worm Composting" featuring our urban permaculture garden, on YouTube click here.

Subscribe to the Modern Farmer channel watch future permaculture segments.

For regular updates about veggie dog Dave and his antics, follow us on Instagram @chefathand.  To subscribe to this blog, sign up here.

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