My The vegetable garden is wild. It’s grass, the weeds have consumed my gardening tools and representatives from all kinds of the animal kingdom – maybe even the jabberwocky – are enjoying a comfortable existence there, eating my salad greens and each other.
Letting go of things seems like a good idea. I recently learned about carbon-positive agriculture, sometimes called carbon farming, and wanted to apply the small-scale suburban principles to my Blue Mountains vegetable and fruit growing efforts. The goal: always more stewed tomatoes, huge zucchini, sweet raspberries and a bunch of tart, juicy apples.
Carbon-positive farming (or horticulture) is a simple concept: remove carbon from the air and put it in the soil. In agriculture, it provides a potentially significant part of the solution to the crises of global climate change, caused by excess carbon in the atmosphere, and decreasing soil fertility, caused by the loss of carbon in the soil.
Carbon does the job better, says Prof Budiman Minasny, a soil scientist at the University of Sydney. “Trees, plants, animals, bacteria, when they die, they form organic matter in the soil, and a large part of it – more than 50 of it – is carbon,” says Minasny.
That organic matter helps the soil form ferns that allow water to disperse, holding and providing the nutrients plants need. The more it is in the ground, the healthier it is.
The most obvious way for gardeners to return more organic matter to the soil is by composting all plant-based organic waste, including leaves. “The compound actually helps to break down all the leaves and other things into a more stable form of carbon; That means it’s not released quickly,” Minasny says.
His back is always full of leaves, but instead of throwing them, he collects them and places them on the ground.
There are techniques for composting to avoid generating too much methane – a powerful greenhouse gas – and to dispose of your organic waste properly. That means replacing your nutrient-rich kitchen waste with less nutritious materials such as leaves, grass clippings or even shredded newspaper or cardboard. If there is no space for a compost bin, you can work by digging a kitchen shovel directly into the soil.
In agricultural fields, one carbon-positive technique that achieves treatment is low till or no till farming. Cultivation – turning the soil – releases a lot of nutrients for crops, but it also releases a lot of soil carbon into the air. Low or no cultivation involves rolling the soil into narrow channels for planting, or even planting only in scrub, not cultivating the rest of the soil. The rest is just quiet.
I tried. Somewhere in the backyard I planted three cabbage plants three months ago. I think I already burned the weeds and ate them for breakfast. the chalk as if they failed together.
Prof Alex McBratney, from the University of Sydney, is not the only scientist keen on backyard gardens. “I am old,” he said. “I gardener would be well kept.”
Better cover the crops, he said. This term describes plants specially bred to prevent erosion, slow the growth of weeds, retain moisture, increase nutrients, and reduce the risk of pests and diseases, which are also a key part of carbon-positive agriculture.
Traditionally, backyard gardeners grow fruits and vegetables in the spring and summer, then harvest and leave the soil largely through the fall and winter. But if every gardener plants a crop and harvests it, while doing nothing else to improve the soil, then overall it will probably help the amount and quality of carbon in the soil over time, losing it both in terms of crop production, but also in carbon lost to the air and erosion.
Cover crops put nutrients — especially carbon and nitrogen — back into the soil that fall, can help control pests and diseases, and help suppress weeds. McBratney suggests planting a mix of grains (e.g. rye or buckwheat) and legumes such as peas and beans, with a few cabbages — cabbage, cauliflower or cauliflower, for example — that help control fungal diseases.
“You just have to grow them to grow biomass above ground and grow nitrogen and biomass underground,” McBratney says. The vegetables do not need to be wrapped; they can lie on the ground, then really dig into the soil.
A more controversial technique in agriculture is the addition of carbon as biochar; a form of carbon made from organic matter burned in low oxygen conditions. It undoubtedly adds carbon, but whether it achieves a greater reduction in atmospheric carbon is debatable. McBratney says if you have woody material that can’t be composted, and you can burn it in a covered pit as biochar, “it can have some benefits for the nutrient and microbial population.” Biochar can also be purchased from plant and film stores.
A simpler technique, at least in sandy or light soils, is to add some clay, mixing it with water and watering it into the soil. “The more clay you have, the easier it is to retain or increase carbon,” he said.
After a brutal, hot weekend, the tall grass was yanked out – with as little disturbance as possible to the surrounding soil – and rested on the surface of the earth, in the hope of returning some of that grass carbon to the soil as it were. neutralizes and reduces moisture loss. A multitude of earthworms have moved through mass relocation from my compost bin and the newly bare earth has been patchily covered in grass clippings and cardboard. Now I’m just waiting for the sun and the rain to do their job.