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Public Lab Research note


How To Become a Carbon Gardener

by laurel_mire | September 29, 2021 20:28 29 Sep 20:28 | #27813 | #27813

Become a carbon gardener and turn your backyard into a carbon sink to improve soil and air quality, reduce surface and air temperatures, restore biodiversity, & help combat climate change!

Motivation

I am an amateur gardener. And by that I mean I was overwhelmed by all that I can and perhaps should do to maintain the green bits of land surrounding my home. While trying to concoct a plan to make my garden beautiful, functional, and good for the planet, I came across the idea of being a “carbon gardener”---a gardener who works to increase the amount of carbon stored in their soil and garden ecosystem. I’ve chosen this route because, while increasing carbon storage is one relatively simple goal to work towards, there are many ways to go about it and many additional benefits that will spring up in the process.

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Why Increasing Carbon Storage In Your Backyard Is Worthwhile

Improving your soil’s health goes hand in hand with increasing the amount of carbon stored in it. By focusing on ways to sequester more carbon in your soil, you can create a ripple effect of benefits that begin in your own garden and stretch out to help the whole biosphere.

The goal of carbon gardening is to increase carbon sequestration (or storage) in your soil and vegetation. Like larger scale carbon sequestration efforts like the much-debated carbon capture and storage method, carbon gardening can decrease the amount of CO2 in the atmosphere by increasing the amount of CO2 stored in the Earth. This in turn helps mitigate climate change. I’m not saying that one home garden is going to solve this global scale issue. However, the power of individual action working towards a collective goal is important, and, because carbon gardening has so many benefits, why not better the whole Earth while bettering your own slice of it?

How It Works

Carbon gardening aims to increase carbon sequestration---the process of absorbing and storing atmospheric carbon---in your garden by helping soil store more carbon for longer than what would occur otherwise. As shown in the simplified soil carbon cycle below, carbon storage occurs naturally in healthy soils. The main players are plants and soil. Plants take CO2 from the air, process the gas, break it apart, deposit carbon into the soil, and release oxygen. The soil then stores this carbon.

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Image courtesy of The Conversation via Yahoo!News https://news.yahoo.com/soil-carbon-valuable-soil-carbon-134539933.html

Carbon is held in soil in 3 different ways, or pools, depending on how long the carbon storage lasts. The “fast pool” is made up of plant residue and stores carbon only for a few days or a few years. The “slow pool” may store carbon for years to decades and includes carbon stored in processed plant material, microbial residue from the fast pool, and soil aggregates. The most important pool for the most effective carbon sequestration in soil occurs in the “stable pool”, which may hang onto carbon for centuries to millennia. The stable pool is found at least a meter below the surface and contains humus---decomposed organic material made from the process of humification. Humus is an aggregate of sand, clay, and silt held together by a gluey protein called glomalin. Glomalin is made by mycorrhizae (fungi) in the soil and is made up of 30-40% carbon in a very stable form.

In short...soil that is high in humus is soil that is excellent at sequestering carbon because its carbon is held in such a stable form. I’m sure any soil experts and botanists out there have much more to say about this, so please contribute!

What To Do and What Not To Do

What To Do What Not To Do
- Leave lawn clippings and let fallen leaves
accumulate under trees and shrubs
- Plant at least 80% native vegetation
- Diversify! Mimic nature as best you can
- Choose perennials over annuals
- Use synthetic NPK fertilizers
- Plow, till, or extensively dig
- Leave your soil bare for extended periods of time
- Plant lots of wildflowers or anything that says "instant"

Healthy soils store carbon naturally. So in simplest terms, carbon gardening is just helping nature along.

Synthetic NPK fertilizers shut down natural production of nitrogen (an element crucial to plant growth and photosynthesis) and in effect slows or may completely stop humus formation and deep carbon storage. However, stopping fertilizer use cold turkey will leave your plants unprepared to thrive on their own. Expert carbon gardeners suggest using the 20-30-30 reduction regime, tapering off fertilizer application by 20% the first year, 30% the following 2 years, and then completely by year 4. Although it may seem unnecessary, a slow reduction of fertilizer use invests in your long-term garden health and cutting out fertilizers completely has lots of benefits. First, you’ll save money. You’ll also reduce upstream energy inputs and carbon emissions required to make fertilizers and downstream effects like nutrient loading and eutrophication of waterways. Lastly, many fertilizers contain harmful chemicals and can be toxic to humans and wildlife. So reducing their use helps clean up waterways and encourage a healthier ecosystem. Instead, you can use lawn clippings and fallen leaf matter that are full of yummy nitrogen. Letting dead organic matter accumulate will help naturally increase nitrogen in your soil. Plus, it's hard to find a much easier method than just letting nature be.

In its most passive form, carbon gardening is about trying to minimize soil disturbance and keep carbon in the soil rather than releasing it into the air. Perennials will store carbon longer than annuals because they do not need to be replanted each year, a process that releases carbon stored in soil. For the same reason, adopting a no plow and no till policy also lets carbon remain in your soil for longer.

What To Plant

Native Plants

Likely any gardener knows the importance of incorporating native plants into your garden. Carbon gardeners are no exception. I initially thought there would be some magic list of the “best” plants and trees for storing carbon. And while there are definitely some that are better than others, native plants will still be the best for each particular location. A study from New Zealand found that even planting the “best” non-native trees still released more than 2.5x more CO2 than native trees. This has to do with the slow growth rate of native vegetation rather than often rapid-growing exotic species. Use this Native Plants Finder from the National Wildlife Foundation to see what’s best for your location. (NWF also ranks each native plant by the number of butterfly and moth species supported by each species!) As a bonus, native plants are also more likely to survive local weather and support your local ecosystem with habitat creation and a food source for native wildlife. They also don’t need to be pampered if your soil is healthy, again avoiding fertilizer and cutting costs.

Grasses

It is often assumed that trees are the best option for storing carbon. However, grasslands are actually even more efficient carbon storers than trees. Some native grasses in North America include black-eyed susan, milkweed (bonus points for supporting monarch butterflies!), and gaillardia. Grasses are also more ideal in fire and drought-prone areas as they can recover much faster than trees and begin sequestering carbon again.

Shrubs

Shrubs have similar advantages over trees as grasses do. A shrub is a woody plant with multiple stumps that branch close to the ground. They are very adaptable because they can regrow easily after disturbance, grow much faster than trees, and are an active citizen in a healthy, biodiverse, carbon-sequestering soil system. (Shrubs trade nutrients with fungi and shelter microbes, enhancing soil health). Shrubs are crucial to establishing community health in a garden and encouraging ecological relationships between multiple species. Especially for midwesterners, shrubs are a great addition to your garden and yard because much of the natural shrubland of the Midwest has been destroyed. Check out dogwood for dry areas, chokecherry for shady areas, and hardy, drought-tolerant junipers that can grow anywhere in the US.

Trees

Trees are still quite good carbon storers, but which tree is “best” will again depend on location and what you may need. For example, choosing a tree tolerant of pollution and road salt may be best for urban and suburban areas. One study from New York found that tulip trees removed the most pollutants from the atmosphere in addition to sequestering carbon. Pines are also a great option as they decompose slower than other trees and thus store carbon for longer after the tree dies.

A Note on Lawns

Lawns are sometimes seen as an enemy to the environment and to natural ecosystems. However, many of us in suburbia are likely rather attached to our green lawns. Thankfully, there are ways to improve your patch of grass.

  • Let your grass grow longer. This will reduce lawn mower use and allow your grasses’ roots to grow deeper, resulting in fewer weeds and less need for watering.
  • Mow higher. Set your mower to 3”.
  • Leave your grass clipping on the lawn to compost in place (clippings are full of nitrogen)
  • Add native grasses as opposed to “turf grasses”. They have longer roots and will sequester 20-40x more carbon than turf grass
  • Overseed with Dutch white clover
  • Increase the size of your non-lawn areas as much as possible

Find much more detail about bettering your lawn for the environment here: The Polyculture Lawn: A Primer (ecologicalgardening.net)

Conclusion

The Earth’s soils contain over 3x the amount of carbon stored in the atmosphere and 4x the amount in living things. They are a huge resource for taking in excess CO2 in the atmosphere and fighting climate change. Adopting the techniques of carbon gardening can contribute to this important function of the Earth’s soils while gaining the many benefits of an overall healthier garden and local ecosystem.

I’ll be incorporating some of the practices of carbon gardening into my own yard and learning more as I go! If anyone has any other tips or tricks, let me know! Happy gardening!

More Resources

Background of Carbon Sequestration and Soil Health

What To Plant


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