Composting, Cover Crops, and Carbon Sequestering

Building climate resilience with gardening.

Composting, Cover Crops, and Carbon Sequestering
Photo by Sandie Clarke / Unsplash

This post is for the gardeners, the people who spend their time digging and planting flowers, vegetables, shrubs, and trees - I love you all. I come from a family of old-school farmers and gardeners, so growing plants is in my blood. My partner is a big gardener, my parents were gardeners, and I love fighting for natural habitats that support dwindling flora and fauna.

Imagine my surprise that composting, in conjunction with cover crops, can capture and store over 12% more carbon in the soil. That’s what a 19-year study by the UC of Davis found, and I’m tickled pink!

For their 19-year study, published in the journal Global Change Biology, scientists dug roughly 6 feet down to compare soil carbon changes in conventional, cover-cropped, and compost-added plots of corn-tomato and wheat-fallow cropping systems. They found that:
Conventional soils neither release nor store much carbon.
Cover cropping conventional soils, while increasing carbon in the surface 12 inches, can actually lose significant amounts of carbon below that depth.
When both compost and cover crops were added in the organic-certified system, soil carbon content increased 12.6 percent over the length of the study, or about 0.07 percent annually. That's more than the international "4 per 1000" initiative, which calls for an increase of 0.04 percent of soil carbon per year. It is also far more carbon stored than would be calculated if only the surface layer was measured.

I always knew that gardeners loved the earth but now they can be on the front line to fight against climate change.

What is composting

Composting is recycling decaying organic matter for fertilizer or conditioning the land. Almost every gardener I know does some level of composting for their flower and vegetable beds.

My family composts all our vegetable scraps. We compost our tea, coffee, and other organic matter. Removing these organic scraps is a great way to reduce the amount of garbage we throw away too, so that’s another win in my book.

Composting helps enrich your soil with good nutrients for your plants to grow but that’s only part of the equation. Fixing nitrogen into the soil is the other part and that’s where cover crops come into play.

What are cover crops

Cover crops are plants you grow that “have the potential to increase soil organic matter and fertility, reduce erosion, improve soil structure, promote water infiltration, and limit pest and disease outbreaks.” (Via Ucdavis)

Cover crops come in a variety of types, ranging from grasses like buckwheat, rye, and wheat to legumes like white clover and fava beans. The goal of cover crops is to "fix nitrogen" from the air and move it into the soil. This is done via a symbiotic process with soil bacteria.

The combination of composting and cover crops is a big thing in the no-till, crop rotation, and organic farming movement. Strong healthy plants are resistant to pests and diseases and won’t need pesticides.

Climate resilience and food security

I wrote an article about food security being the new wealth in a +2C world. Climate change will alter how we grow food and everyone will need to learn how to grow food, either to supplement what we have or feed us 100%.

Understanding the soil is part of building climate resilience and we need to brace ourselves for the coming heat waves, droughts, and climate disasters. We need to fight with all our might to slow down climate change and turn the tide of the war.

Gardening and sustainable practices like composting and cover crops are part of the battle against climate change. We gardeners are like the Riders of Rohan in the Two Towers that arrive at the first light, on the fifth day.

I don't subscribe to the idea that the battle is lost. There is a chance to stop the damage we’ve done but it’s a multi-front war. We just have to pick which battle to wage and which friends will fight beside us.


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