By Darlene Belton, Master Gardener
The soil in your garden is constantly being depleted by you, the conscientious gardener. Whenever you harvest your herbs and vegetables, or clean the garden in spring or fall, you remove material filled with nutrients that had been transformed into plants. Over time with this practice your soil loses its ability to promote the health and productivity of your garden. In a forest, however, dead plant material falls to the ground to be reabsorbed into the earth to nurture new generations. So, how can we, non forest-dwellers but concerned regenerative gardeners and ecosystem managers, reverse this human-induced pattern of net loss?
Well, mulching helps, but the annual application of well-prepared compost is better yet. You can even be quite strategic about how you build healthy soil that works for whatever garden plants you have.
To explain the strategic part, we need to begin with nature’s universal botanical drive to create a forest, a process scientists call succession. At the start is a disturbance event such as fire, earthquake – or tillage – that destroys existing vegetation and lays bare the earth, destroying soil microorganisms especially fungal mycelia. The first plants able to grow in the depleted soil are pioneer plants many of which we call weeds, whose focus is the rapid production of seeds that begin to colonize the area (sound familiar?). As litter from dead pioneer plants accumulates, providing food first for soil bacteria then fungi, the earth becomes able to support more complex plants in a quite standard order of succession – annuals, grasses, perennials, then shrubs, small trees, larger trees and finally old-growth conifer-dominant forests, at least until the cycle begins again or is reversed somewhat through later disturbance events of varying severity.
During succession the composition of the soil biology actually changes, becoming richer in fungal diversity as mycelia attach to plant roots to proliferate by trading the minerals and other nutrients they have mined at a distance for the sugars plants create through photosynthesis and exude through their roots. The resulting immense network of fungal mycelia has been called the nervous system of soil. The amount of information that is passed among the tightly interconnected and diverse plants in a given ecosystem helps the plants fight off pests and disease, as well as obtain essential nutrients including water.
What then does succession have to do with your compost bin? Well, as gardeners, we mostly operate at the earlier stages of succession, from disturbance (tillage) through annuals (flowers and vegetables) to small trees (often fruit-bearing). Such soils, when optimally functioning to support these succession stages, are bacterial- dominant or balanced. Our soil workforce of bacteria and fungi is alive and therefore needs food, which at least at the first trophic levels is supplied by nitrogen (greens) and carbon (browns). Higher trophic levels in the soil food web tend to eat each other – but the health of the food web depends on the proliferation of lower levels. It is easy to see now why compost is needed for soils that are regularly robbed by the removal of dead or harvested plants as happens in our gardens.
Compost is more biology (living matter) than ‘material’ (dead plants) according to Doug Weatherbee, a protégé of Dr. Elaine Ingham (see Grow Column July 2021 MMGA newsletter), who gave a three-day workshop on composting for the Harvest Moon Permaculture Institute in Clearwater MB that I attended in 2012. He said you should ask yourself, “What kind of plants do I want to grow?” and “What kind of soil do I have now?” and then match the N:C (green/brown) ratios to suit your target stage(s) of succession (see diagram). However, erring on the side of brown (food for fungi) is never a problem, as he said most soils are very depleted in fungi that support the health and disease resistance of plants. Healthy compost smells good, he said, like forest earth, and is a deep brown to black.
“If it smells bad, it is bad,” (due to lack of oxygen creating anaerobic conditions) Weatherbee told our group. Anaerobic compost contains pathogens and suppresses good microorganisms. Regular turning infuses oxygen and, along with judicious amounts of water (compost when ‘hand-wrung’ should yield about one drop of water, similar to clothes from a spin cycle), ensures aerobic compost that is infused with health-giving microorganisms. In fact, you can inoculate your compost by adding small amounts of soil from, for example, a forest floor or a healthy wetland, or even compost from a vigorous pile – something I did recently after bringing samples back from a visit to a friend’s regenerative farm. The microorganisms from these sources should multiply in my compost, improving it as a soil additive for when I lay it out on my gardens this fall.
My home composter. On the left, ingredients ready for mixing. From bottom left, fresh chemical-free grass clippings, pail of well-rotted grass-fed cattle manure, wood chips, and shredded fall leaves. Note the construction - hardware cloth for ventilation on the sides and removable wooden slats for ease of turning. These ingredients were mixed with the existing compost to encourage the proliferation of ‘good’ microorganisms. On the right, the bins with the new ingredients mixed together and wetted.
Perhaps it is not necessary to get too technical about compost, however. Manitoba’s Green Action Centre promotes backyard composting throughout the province by offering the Master Composter program plus how-to videos and an informative website (https://greenactioncentre.ca/reduce-your-waste/composting-basics-and-getting-started/ ). Master Gardeners and Master Composters, Karen Loewen and Lori Graham found the intense 20-hour program both fascinating and very doable. Both still practice the balanced composting method taught by the Green Action Centre: equal amounts of greens (veggie scraps, grass clippings etc.) and browns (straw, shredded fall leaves, wood chips etc.) placed roughly in layers and turned about once a week through the growing season, even added to in winter but not turned when frozen.
This is a cold compost, Lori says, the easiest type for backyard systems, and it works well though it can take up to a year to be ready to use, depending on how often it is turned, how finely the ingredients are chopped, and whether the pile is in sun or shade. Because cold compost doesn’t heat up enough to kill pathogens or weed seeds Lori is careful when adding weeds (otherwise very nutritious food for soil microorganisms) and does so before seeds form. As well, she doesn’t add either tomato plants or rose clippings as these are known to harbour diseases. She also avoids plants that rabbits love to eat after the experience of finding a half-buried nest of baby rabbits in her compost one year (see photo). Now, just in case, she runs her hands through the top layer of compost before turning it to avoid killing any hidden bunnies.
Hot compost requires more attention, both in turning it every few days when the temperature in the pile’s centre reaches 55-60C as measured with a compost thermometer (a bin at least the size of 3’X3’X3’ is needed to reach these temperatures), and in ingredients used – for example high N (nitrogen) can be supplied by chicken manure that allows for the buildup of sufficient heat to kill pathogens and weed seeds (high N is not required for cold compost, as regular greens suffice). Karen was drawn to enroll in her compost course after reading that European countries are often very advanced in composting, including ingredients such as clothing so that almost nothing goes to landfills, unlike here in Canada. Karen says that even now, after moving to a smaller yard, she is looking for a tumbler-style composter to return to the level of composting she enjoyed formerly with two 4’X4’X4’ bins that produced a lot of compost for her many former gardens.
Karen found a fun and effective way to encourage composting in her community by enlisting young school children. She responded to teacher invitations sparked by her grandchildren to speak to their classes. She discovered that giveaways of plastic insects, candy ‘gummy bugs’ (not to mention the chance for the ‘hands in dirt’ of composting demos) excited the children who took the message home to their families.
Vermicomposting – composting by feeding worms and harvesting their castings (euphemism for ‘poop’) – is a method I haven’t tried, unsure as I am about where to place a bin of worms chomping on kitchen scraps in my open area home. However, worm castings are ideal food to build healthy soil microorganisms. Glenn Munroe, host of the Compost Council of Canada’s webinar series aired in early 2021, attests that the non-native red wiggler worms used can survive Canadian winters in insulated outside housing. I’m not sure if Glen has experienced a Manitoba winter, though, so I remain to be convinced. Lori has purchased worm castings from a commercial supplier, however, and used some of it to make a worm casting extract: 1/4 cup castings to two liters of water, or multiples thereof, that she lets sit for 48 hours then uses in planting holes in the spring.
A great time to lay compost in your gardens is in the fall. The newly emptied bins can be filled again with mulched grass and fall leaves from your own and neighbours’ yards – plus chopped garden waste – to start the process again before winter. Add kitchen scraps on your frozen pile over the winter and you will be off to a good start after the spring melt. With regular turning your compost should be ready for use in planting holes and to boost your gardens’ health and productivity as spring turns to summer 2022.
Published: September 2021