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Concentration of CO2 in the Atmosphere

No-Till Gardening: Good for Crops and the Environment

Image: rootsimple.com

Jessie Haas

Most people don’t realize that we are living through two carbon crises (plus a pandemic, plus mass political craziness. I know, right?) We have too much carbon in the atmosphere and not enough in the soil, and there’s a connection: between 50 and 70% of the carbon in world farmland soils has been off-gassed due to tillage. Plowing, cultivating, and harrowing has sent 792 billion tons of carbon into the atmosphere in the past 250 years.

Tillage also introduces excess oxygen into soils; that temporarily provides abundant growth, but it also increases the decomposition of soil organic matter (SOM). Tillage is mining the soil of carbon, putting it where it doesn’t belong and heating the planet. It’s also depleting soil fertility and reducing the nutritional value of crops.

These twin problems, though, are actually a huge opportunity, and one that Cedar Circle Farm and Education Center in East Thetford has been exploring. For the past five years, the farm and education center has been experimenting with various forms of no-till vegetables growing on crops such as broccoli and kale. They have used rollers to crimp and kill cover crops (without using Roundup, one of the drawbacks of mainstream no-till), and also the extremely low-tech methods of solarizing and occultation. Solarizing is covering a piece of ground with clear plastic for a short period, usually just a day or two in warm, sunny weather. This kills weeds, weed seeds, and slug eggs and leaves a bare seedbed for planting. Occultation is the same process done much more slowly using tarps put on black side up.

No-till vegetable garden. Image: Flickr/Jackie Caserta

Cedar Circle has put in its strawberry plants for the 2021 season, and has experimented with planting directly into a crimped and solarized cover crop. The bed looks as if it’s already been mulched. To test the theory that no-till helps soils retain moisture, the Cedar Circle team has installed a soil moisture reader in the experimental bed and another in the traditionally planted bed a few rows over. It will be interesting to hear about the results.

No-till scales in both directions; many dairy farmers drill seed directly into killed cover crops, and home gardeners can use the techniques as well. It’s not too late to get started; cover crops are an important part of building soil carbon, and many cover crops, such as buckwheat, oats, and annual rye grass, can still be planted. They may not reach maturity before frost, but that’s okay. They will still feed soil microorganisms with their living roots, and build SOM once they’ve died and fallen, contributing their incorporated carbon.

No-till field of peas and oil radishes, after harvest. Image: Volker Prasuhn, Wikimedia Commons. https://bit.ly/3blLvB4

SOM is 58% carbon, and that carbon is what allows the microbial soil network to digest minerals and trade them with plant roots. Without adequate carbon, plants lack nutritional value. SOM also helps soil aggregate, creating structure that lets it store more air and water. It builds an absorbant soil sponge that is resilient to both drought and excess rainfall. And it can be a key to farm profitability. Many market gardeners who switch to no-till find they no longer need a tractor. This helps lower the costs of getting into farming. It can also allow a marginal piece of land to be made productive; many no-till market gardeners build their soil literally from the ground up with manure, compost, and cover crops.

No-till is a climate solution that anyone can participate in. Grow Your Soil!, by Diane Miessler (Storey 2020) is a cheerful, practical resource for home gardeners who wants to draw down carbon in their own front yards. Miessler happily accepts weeds as cover crops and details methods for ‘chop and drop’ weeding, where you simply cut or pull the weeds and leave them where they are, covering them with mulch to prevent the garden from looking too messy. Another good resource, geared to the market gardener, is The Organic No-Till Farming Revolution, by Andrew Mefferd (New Society Publishers 2019). There are multiple resources for large-scale farming; one of the most inspiring is Dirt Into Soil by Gabe Brown (Chelsea Green, 2019).

If gardening is not your thing, you can still ask at the farmers’ market if the produce you are buying is grown by no-till methods. If farmers hear that customers are interested in buying no-till crops, they will start thinking about growing them. Any moves in that direction help solve both climate crises and the what’s-for-dinner crisis in one fell swoop.

Jessie Haas has written 40 books, mainly for children, and has lived in an off-grid cabin in Vermont.

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