No-dig gardening easier on the planet and the back
What’s your gardening style? The way we garden can determine whether we are increasing or decreasing greenhouse gases such as carbon dioxide. Carbon has been on my mind lately following the release of the alarming 2021 report “Climate Change 2021, The Physical Science Basis,” from the United Nations’ Intergovernmental Panel on Climate Change.
The forests and grasslands, which existed before today’s extensive farms and development, were constantly returning organic matter to the soil as they grew and reproduced, died, and regenerated.
Our ancestors fertilized with bedding straw and manures, but in most of today’s agriculture, the soil is tilled and planted, with chemical fertilizers and pesticides added, but little organic material is returned to the soil.
When organic materials in the soil, such as roots and leaves, dead insects, and compost and mulch that we add are decomposed by microorganisms the remaining matter becomes humus, which among other things, is the basis for carbon storage in the soil. Much of the reason humus is black is because of its carbon content so you can get an idea of how much carbon is stored in your soil by how dark it is.
Humus, which is stable and resistant to decomposition, is approximately 60 percent carbon, which can remain undisturbed in the soil hundreds, even thousands of years, until it finally decomposes completely and returns the carbon to the air. Deforestation and poor farming (and gardening) practices over the past century have depleted carbon in the earth’s soil by as much as 50 percent.
Returning carbon to the soil
According to the IPCC report, carbon dioxide levels in the atmosphere are higher than they have been for hundreds of thousands, possibly millions, of years. Returning carbon to the soil is one of the remedies.
In a previous article, I recommended home landscapes as a good place to sequester carbon, but what about vegeta
ble gardens? A vegetable garden is not a very stable environment. We are constantly tilling and digging, changing crops, and pulling up plants and weeds. That’s a problem. When we disturb the soil, we release carbon stored there. When exposed to air, the carbon combines with oxygen and becomes carbon dioxide.
We can help return some of the missing carbon to the soil for storage by adding organic material to our gardens. Mulches of leaves and straw, compost, and cover crops replenish the organic matter needed to create humus, nourish plants, and store carbon.
Another way to help reverse destructive carbon depletion is no-till gardening. You can start a no-till garden from scratch or transition from traditional gardening to no-till over the course of several years.
No-dig bed can start with cardboard
No-till, sometimes called no-dig, is an easy way to create a raised bed garden on turf or some other permeable surface. It requires no digging, leaving carbon stores undisturbed.
Start by laying down one or two layers of cardboard over the footprint of your raised bed, and several feet beyond if you want mulched pathways around the bed. If the soil is particularly compacted, it’s a good idea to loosen it with a broadfork or garden fork, or even a lawn aerator, before laying the cardboard.
An optional layer of compost on the surface under the cardboard will jump start production of the soil life needed. When the cardboard is down and the raised bed has been built or placed on top, poke holes in a number of places through the cardboard so water doesn’t accumulate to drown roots once garden soil has been added. Wet the cardboard well.
If a raised bed is more than eight inches deep, a good option is to first add sticks, leaves, and other yard debris such as banana leaves and stalks. This provides immediate material for decomposition and reduces the cost of filling the bed.
Fill the top six to eight inches with your choice of compost and garden soil, add some mulch to hold in moisture and suppress weeds, then plant seeds and seedlings. Just move the mulch aside where you want to plant.
Cardboard kills weeds and grass
The cardboard will kill any weeds and grass beneath, adding them to the soil as organic matter. Over the next six months to a year the cardboard (also organic material) will also decompose, worms and microorganisms will soften the earth beneath, and soon you’ll have deep, fertile garden soil well on its way to becoming humus.
At this stage it’s a good idea to plant root vegetables such as carrots, beets, turnips, and daikon radishes to further loosen and aerate the soil and allow carbon stores to merge deeper into the earth.
Once your raised bed is established, you can garden traditionally or continue with no-till methods to retain carbon stores and continue feeding your plants with organic matter. In raised beds or gardening in native soil, no-till involves cutting your healthy vegetable plants and cover crops at the soil surface and dropping them in place to act as mulch, and planting cover crops or new vegetable crops among the dropped and decomposing plants.
Cover crops prevent bare soil
Microorganisms, including the extensive webs of fungi necessary to sustain plants, are undisturbed. No-till gardening creates a more stable garden environment, reduces the release of carbon, conserves moisture, discourages weeds, prevents erosion and leaching, and provides a steady slow-release supply of nutrients for crops as mulched plants decompose.
It works best when cover crops are planted between vegetable crop seasons so that the soil is never bare. Pioneer plants (weeds) will soon take root where soil is bare.
Transitioning from traditional gardening to no-till requires a period of several seasons of weeding and management. But eventually, if crops are rotated, cover crops are thick and diverse enough, and new weeds are not allowed to seed out, weeds, pests, and diseases will be discouraged, and less care will be needed.
It’s a great way to garden.