Here we are now, midway between winter solstice and spring equinox! The skies are still grey, yet buds are swelling everywhere and the birds are starting to make a lot of joyful noise. A few days ago I went out into the garden late at night. I stood in the darkness transfixed, listening to that intense rustle and bustle within the leaf mulch. It was like hearing the earth eat and breathe. It’s happening again!
While preparing for the busy spring season, I keep thinking back to the Soil Biology course, put on by Soil Food Web Canada back in November. Was that ever fun! Picture a classroom full of adults gazing through microscopes and shrieking with delight at the discovery of a live wriggly nematode, a hairy ciliate, a long fungal strand, or a fantastically shaped amoeba…
And highly useful it was too. So I wanted to share some insight on how to produce high quality compost, for use on its own or for making high quality compost tea. It is possible to customize a recipe depending on what you want to use the compost for; and that depends on the preferences of the plants you wish to grow. For example:
Grasses have a preference for bacteria in their soil – more so than for fungi. So if you’re installing or maintaining lawns or growing grains, and you want to give the soil biology a boost, you would add a bacterial dominated compost (or compost tea). If you’re growing annual flowers, herbs, or vegetables, it’s useful to know that these plants like about equal proportions of bacteria to fungi. When it comes to ornamental shrubs, berry bushes, vines, fruit trees, and other deciduous trees, these plants have a preference for fungal dominated soils. Coniferous trees even want up to 1000 times more fungal mass than bacteria!
This does not mean grasses don’t like fungi, nor does it mean trees don’t need bacteria – they both do. This is simply an indicator of whose dominant presence they prefer.
Now in order to make the appropriate compost for your plants, you can choose the types and amounts of starting materials that support either more bacterial or more fungal growth.
Here are some rule of thumb numbers:
Bacterial compost: 25% high N, 45% green, 30% woody/brown materials Fungal compost: 25% high N, 30% green, 45% woody/brown materials
You probably know your greens and browns, but what is “high N”?
Greens: fruit and vegetable waste, coffee grounds, grass clippings, fresh leaves, weeds, hay, etc. Browns: dry fall leaves, straw, shredded newspaper and cardboard, sawdust and woodchips, etc. As for high N (nitrogen) materials, that would be manures, seaweed, okara (soybean waste from making tofu), or alfalfa. Use manures cautiously.
To further support microbe populations, you can add molasses or plant juices to bacterial compost, and humic acids or fish hydrolysate to fungal compost. It is generally quite easy to make bacterial compost, because bacteria are naturally the first organisms to arrive on scene where there is organic matter to be broken down. Fungal compost may take a little more effort.
Yet another way of tipping the scale is to mix in a bit of topsoil from a healthy meadow when starting a bacterial compost, and some earthy smelling forest soil into a fungal compost. It all comes down to creating an ecosystem at the same time as building a garden!
Of course there is much more to making compost – once your pile is built, you want to monitor and manage temperature, moisture, and air content. This is just about different ways to start out.
Enjoy the changing of the seasons!