Storing Carbon In Your Own Backyard

compost
Making and applying compost adds organic matter to the soil. Photo by Robyn Rosenfeldt

Regenerative agriculture is attracting a lot of attention as a way to reverse declining soil fertility while pulling carbon out of the atmosphere and stashing it back in the ground. Yet, restoring soil health is not just for farms. It is something we can do in urban places, too, and gardeners can lead the way in their small corners of the world.

Proponents say that regenerative farming, if adopted broadly, could help slow the rate of global warming. With better management, global croplands could store up to an additional 1.85 gigatonnes of carbon each year, or as much as the entire transportation sector emits.

Researchers at the Rodale Institute calculated that replacing conventional farming practices around the world with regenerative ones would allow us to sequester 100 percent of annual global carbon emissions.

This means the way we grow food could help save our planet. It requires major changes in the way farming is practised. Planting a monocrop over vast amounts of acreage, leaving the soil bare for long periods and relying on regular cultivation accelerates the loss of healthy topsoil and releases buried carbon into the air. It also prevents water retention in the soil, through loss of groundcover.

Poor soil structure can mean plants develop weak root systems and makes them more vulnerable to pests and disease. This necessitates higher levels of chemical fertilisers and pesticides that, in turn, kill the beneficial organisms in the soil that feed plants and help make the soil rich in carbon.

How Soil And Plants Draw Down CO2

About half of the carbon released into the atmosphere every year is absorbed by oceans, plants, animals, air and soil. Soil does most of the heavy lifting, storing four times more carbon than plants. We interrupt this cycle by ploughing it, stripping it of forests, spreading chemicals on it and leaving it bare – and this has terrible consequences. When soil degrades, the molecules that bind carbon break down, releasing it back into the air.

Regenerative practices grow food in a way that returns atmospheric carbon back to the soil, a process called sequestration. It starts with plants, through photosynthesis, the process by which light energy is turned into plant food.

Every morning, the sun stimulates plants to suck down carbon dioxide. The carbon is shuttled through plant cells, picking up new elements along the way, such as hydrogen, oxygen, and more carbon. Eventually, it comes to rest in plant tissue as glucose and starch. This is how a molecule of greenhouse gas is turned into the carbon-rich sugar that plants use to grow.

The carbon gets worked into the soil by bugs and soil organisms. Leaves fall and branches break off, but decomposing plant debris accounts for only a fraction of the carbon that gets stored underground. Real carbon sequestration happens deeper, at the roots.

Plants release some of the carbon-rich sugars they make through the tips of their roots to attract bacteria, fungi and other beneficial microbes. In exchange for the free meal, these tiny organisms offer access to nutrients that plants otherwise can’t reach; and even help ward off pests and disease. Now those molecules of carbon, originally drawn from the atmosphere, are tied up in the bodies of soil organisms. When they die, that carbon stays deep underground for as long as it’s undisturbed.

Regenerative farming mimics what nature does so beautifully. It leaves plants alone and lets the soil be. In a forest that has been growing for hundreds of years, the plants don’t need any fertiliser, irrigation or pesticides to flourish. When left alone, trees grow, shed leaves and push down roots that support a community of carbon-capturing soil organisms.

Plants growing in favourable conditions like this, with easy access to moisture and nutrients, grow sturdier, more resilient and better able to suck down carbon dioxide. This positive cycle is how nature works when we don’t interfere.

Climate Victory Gardens

Backyard gardeners can incorporate regenerative practices into their gardens and create ‘climate victory gardens’. During World War I and II, the victory garden movement emerged in the USA in response to a growing need to reduce pressure on the public food supply. The government at the time called for

Americans to plant food gardens instead of lawns to feed and support their local communities and troops overseas. Amateur gardeners were given pamphlets about how to grow food and tend their gardens. By 1944, nearly 20 million victory gardens produced 7.25 million tonnes of food; at the time, this was around 40 percent of the fresh fruits and vegetables consumed in the US. It was successful because it connected to grassroots organisers and community efforts. It is an inspiration for today’s Climate Victory Garden movement.

The Climate Victory Garden movement empowers and inspires us to act at the individual and community level. This grassroots effort chips away at much larger issues that otherwise may seem overwhelming and out of reach. If millions of people plant Climate Victory Gardens, it will have a significant impact on climate change. Both then and now, change is possible through the food system.

soil
Soil carbon cycle. Illustration by Joe Wirthiem

How To Create A Climate Victory Garden

Soil test

The first step towards creating good soil is figuring out what you’re starting with. If your land already supports healthy plants, it’s probably in pretty good shape to begin with and your biggest challenge may be weeds. If, instead, your land supports stunted plants and bare, dry patches of dirt, it might make sense to build your soil from scratch or grow your food in a raised plant bed.

A good way to learn what’s going on underground is to get your soil tested. A soil test tells you the nutrient and pH levels in your soil, allows you to fine-tune your fertiliser use and establishes a baseline reading so you can evaluate your soil health over time. It can also alert you to any unsafe toxins hidden in your soil.

Organic matter

Organic matter is the superstar ingredient of healthy soil. It’s the shredded leaves you spread as mulch, the kitchen scraps you add to your compost heap, the old roots left to decompose underground. Basically, it’s anything that was once living. Hungry soil organisms break down these dead leaves, roots and scraps and convert them into plant nutrients, like phosphorus, nitrogen and potassium. This process, known as decomposition, produces humus, a dark brown material that is 60 percent carbon. Humus is very stable and, if undisturbed, can remain in the soil for hundreds or even thousands of years.

Soils rich in organic matter soak up water and nutrients because the molecules are charged, sort of like a static cling. This charge holds moisture and nutrients tight so it’s less likely they’ll evaporate or wash away. Increasing organic matter in your soil by just one percent can increase its waterretaining ability by an extra 75,000 litres per acre.

Increasing the percentage of organic matter in the soil also feeds mycorrhiza fungi, vast networks of fungi that release glomalin. Glomalin is a sticky, gum-like substance that binds together particles of sand, silt and clay, creating a soil structure that further helps to lock in moisture and hold on to nutrients.

Building your plant bed

Building soil from scratch by way of sheet mulching is a great method for starting a new garden. It allows you to build good soil while eliminating weeds, all without digging; plus it works well for just about any space. Creating soil does take time, however, and calls for a hefty supply of leaves, grass clippings, cardboard and other organic material, so it’s not for everyone.

Mulch

Mulch is a backyard carbon farmer’s very good friend. Spreading it helps trap moisture so you won’t need to water your plants as much. It fights weeds, so you spend less time hunched over pulling them out of the ground. It also protects soil, roots and soil organisms against harsh weather elements and it adds organic matter to the soil.

Almost anything can be used as a mulch, as long as it feeds and protects the soil. Pick materials that are inexpensive, easy to find and make sense for the job at hand.

Water your plants, but not too much

Established perennials more or less fend for themselves, finding pockets of water stashed away from the last rainstorm. But annuals like a steady supply. With all the freaky weather that’s happening, who knows when your region will be hit by a record-breaking drought?

Drip irrigation is the best way to ensure a steady supply of water right to the plants that need it. It’s better than using a hose or sprinkler because it uses water efficiently, dripping it right into the root zone. It’s possible to cut your total water use by one third by installing drip irrigation. Drip irrigation also prevents overwatering.

If you’re not planning on installing an irrigation system, you can avoid overwatering by regularly sticking a finger into the soil. If it feels dry at the tip, it’s time to water. If it’s still moist, hold off. For young plants, which need more moisture, water them when the first inch of the soil is dry.

garlic
Grow garlic as a gateway perennial. Photo by Robyn Rosenfeldt

Grow perennials

Planting perennials is one of the best ways to maximise our impact as backyard carbon farmers. These plants have deep roots that provide a safe haven for carbon-capturing soil organisms. They return year after year so you only have to plant them once. And they conserve underground resources, using water and nutrients only as needed, because they’re in it for the long haul.

Annuals, by contrast, are greedy. They grow quickly and die within one growing season, sucking up any nutrients and water their roots can find, whether they need it or not, and releasing carbon back into the air when they die and decompose on the soil’s surface. They have to be planted every year, which means seasonal digging that disrupts communities of the soil organisms we carbon farmers work so hard to cultivate; and they can’t store the amount of carbon that perennials can.

But becoming a backyard carbon farmer doesn’t mean you have to ditch your favourites entirely. If you love growing delicious annuals, like peas, spinach and squash, then plant a few. You can grow anything using a soil-first approach. Heaping on compost and keeping roots in the ground after harvest are just a couple of ways to enhance any plant’s regenerative effect.

There are also plants that are ‘gateway perennials’ like garlic and potatoes. If you leave a few heads in the ground over the winter, a new crop will emerge in the spring, all on its own.

Succession planting

Another way to squeeze more out of your small space is to practise succession planting, which means planting more than one crop in a single space throughout the season. You can plant early-season radishes outside, for example, while waiting for warm-season crops like peppers and tomatoes to grow inside (or under cover). Once you harvest the radishes, you can pop the peppers and tomatoes into their place.

In addition to making efficient use of space, succession planting is a way to make sure your ground is never bare. Keeping roots in the ground is a good way to enhance soil fertility and preserve topsoil, which in turn increases your soil’s carbon-storing capacity.

Fruit trees

Planting trees is the best way to maximise the carbon-storing potential of your garden. The average tree can absorb as much as 22 kg of carbon dioxide per year and will have sequestered about one tonne of carbon dioxide by the time it reaches 40 years old. Plus it will provide you with years of fruit.

Herbs

Herbs are about as accommodating as garden plants get. Once established, they’ll return year after year with very little effort on your part. The nearly bulletproof herbs listed below are great garden companions because their pungent aroma helps deter pests while their dainty flowers attract pollinators. If you’re nervous about ripping out your lawn or just don’t have the space for a garden, planting herbs in containers is a nice compromise. Easy herbs to grow include chives, mint, lemon balm, oregano, sage, thyme and rosemary.

By incorporating these ideas into your backyard garden practices, it’s easy to park some carbon in your own soil. Let’s build a loamy, spongy, dark-brown, microbe-happy foodscape together. It has been done and it can be done, starting with a patch of soil near you.

To learn more about backyard carbon farming, check out Acadia’s books, Growing Good Food, a Citizen’s Guide to Backyard Carbon Farming (Stone Pier Press 2019) and Growing Perennial Foods: A Field Guide to Raising Resilient Herbs, Fruits and Vegetables (Stone Pier Press 2019).

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