Compost Brew for the Soil

One of the greatest shifts in our understanding of optimum plant health is that we’re not actually feeding plants by injecting nutrients into the soil.

It’s commonly thought that adding enough NPK (Nitrogen, Phosphorus, Potassium) plus a few other nutrients is enough to grow a crop.

In a way, it is enough - plants will grow, and may even look fine - but it doesn’t lead to optimum plant health.

Instead, when we feed and support the microbes in the soil, who then feed plants through a complex mutual relationship, we can attain significantly higher levels of plant health - which goes hand in hand with higher levels of nutrition as well as resistance to insects and diseases.

One of the ways to give the soil microbes a boost is with a stepped-up version of “compost tea”.

The effectiveness of this brew will depend on the quality of the compost that is used, so try to use a rich, earthy-smelling compost.

This is a basic recipe… I add several other ingredients when I make it on a larger scale. This basic version should give good results when you’re first learning the process.

Materials Required

  • A 5 gallon bucket (or other sturdy waterproof container)

  • A piece of window screening, thin cotton, or other mesh (to keep flies out)

  • A weight to go on top of the screen, over the top of the bucket (to deter coons and other critters)

  • An old stick or branch, for stirring

How to Make the Compost Brew

The basic process is:

  • Gather all the ingredients

  • Combine them in the bucket

  • Stir it daily

  • Let it brew for 2 - 3+ weeks

  • Strain out some liquid, as needed, to use on your soil


  • Water - preferably rain water (see note below)

  • Good quality, active compost; it should smell rich and earthy

  • 1 cup kelp (use flakes, or crumble it if it’s in large pieces)

  • 1 cup molasses

  • 6 cans sardines, with the juices from the can

  • Some of the optional ingredients:

    • couple cups of wood chip “compost” (wood chips that have been decomposing for at least a season)

    • couple cups of leaf compost

    • handful of worm castings

    • spoonful of ocean minerals (aka concentrated sea water… this is also an ingredient in the foliar sprays that I have found useful)


  • Fill a 5 gallon bucket about 1/3 full of compost

  • Add the kelp, molasses and sardines to the bucket (and any of the optional ingredients)

  • Fill the bucket to within 6 inches of the top with water (this is easier if the bucket is sitting in the location it will be for the next few weeks)

  • Stir everything together thoroughly with an old stick or branch, getting right to the bottom of the bucket

  • Top up the bucket to about 2 inches from the top with water; briefly stir again

  • Cover the bucket with window screening or an old cotton pillow case (single layer, not double layer, unless it’s very thin); securely tie a string around the screening or cotton, to prevent flies from getting in

  • Set a weight over the bucket, to prevent critters from getting it. The mixture needs air, so the top of the bucket shouldn’t be completely covered. For example, set a board over the bucket with several bricks or other weight to hold the board in place.

  • If the bucket is sitting in the open, drape a tarp over it to prevent rain from getting in

  • Stir the contents of the bucket every day or two - or, even stir it twice a day, if you wish

  • The brew is ready to use after approximately 2 - 3 weeks. The exact timing depends on the outdoor temperature; it will be ready sooner when the weather is warmer.


Water: Rain water is ideal to use for this (and for any soil or foliar spray). The next best option is well or spring water. Municipal water can be used too - but it should be allowed to sit in a bucket for 24 hours first, to off-gas some of the chlorine.

Where to set the bucket: in a sheltered place, out of the rain (or, drape a tarp over it, if it’s in the open); away from a door or window of your house, as there can be some odour initially

What to expect

  • Somewhat of an odour, but not a “bad” odour, as in, it shouldn’t smell like it’s rotting

  • The odour will become more earthy with time

  • Everything breaks down, becomes a uniform mix

How to Use the Compost Brew

Main use: as a soil drench, or to wet the roots of your seedlings when you plant them

  • Strain off 1/4 cup of the brew, add to 1 gallon of water in a water can or sprayer. Sprinkle this on the soil around newly-planted seedlings, or over a row of seedlings that are just germinating

  • For drenching roots of seedlings, line a crate or box with plastic, pour the mixture in, and set your seedlings in there for several minutes before planting - they will wick up the water. Alternately, sprinkle this mixture over them (with the above ratio) through a watering can immediately before transplanting them.

This brew can be applied every couple weeks to the soil. Avoid getting it on the leaves of plants that will be harvested soon (eg lettuce). It can be applied to the soil multiple times through the growing season, especially when you are beginning the process of revitalizing life in your garden soil.

Some people suggest adding a source of phosphorus to this type of mixture, each time you dilute some of the brew in water. I’m still working on coming up with a homemade source of phosphorus that would be suitable for this application.

If you’d like to add some phosphorus (which, most plants would appreciate - especially those that produce a “fruit”, such as tomatoes, cucumbers, etc), the best suggestion I can offer at this point is to pick up a liquid organic phosphorus fertilizer at a garden centre. The label will give a ratio of NPK in the fertilizer… look for one with a high level of P (phosphorus). Follow the directions on the label for how much to include in the mix. Depending on the brand, it may be a good idea to cut that dosage in half for this brew.