THE LOW CARBON FOOTPRINT OF ORGANIC GARDENING
We have all heard about rising carbon dioxide gas (CO2) levels in the earth’s atmosphere, which is causing heating, resulting in world-wide climate change. The atmosphere holds about 800 billion tons of carbon at present. Another 560 billion tons of carbon is stored in living plant life. However, the soils of the earth hold the most carbon, about 2,500 billion tons! Forest and grassland soils contain the most carbon, and soils degraded by chemically-drenched agricultural practices hold the least. Rainforest soils can contain as much as 10% carbon of total mass, while the poorest and exploited soils have been reduced to as little as 1% of mass. The process of photosynthesis by plants pulls CO2 out of the air and stores it in living tissues, excess carbon is released through the roots into the soil where it is stored. This process is known as carbon sequestration. Plant roots use living soil fungi (mycorrhizae) in the process. Degraded soils have reduced numbers of these fungi, slowing their ability to sequester carbon.
It is estimated that the world’s agricultural soils have lost 50-70% of their original carbon. Most of that carbon has become CO2 and was released into the earth’s atmosphere. If that carbon could be returned to the earth’s soils, the carbon in the atmosphere could be reduced enough to mitigate global warming and limit heating to 1.5 degrees Celsius. We could do this by changing to organic gardening and farming practices.
Gardening and farming practices that degrade soil are: fallowing, stubble burning, frequent tilling, overgrazing, monoculture cropping and excess application of synthetic fertilizers. All of these reduce the soil’s carbon-holding capacity, soils dry and erode, and CO2 is released into the atmosphere.
Organic gardening practices build living, healthy soils able to sequester much higher levels of carbon. Farming trials in several countries around the globe have shown a rapid increase in carbon in soils where organic gardening and farming methods were employed. A key to this is increasing organic matter in the soil.
Methods known to restore soil’s ability to process and store carbon include: tilling as little as possible or not tilling, mulching, using cover crops, management of crop residues, crop rotation, and proper irrigation.
If you are preparing a new garden space, place a heavy mulch of rotted, damp straw and compost or manure (or bedding from livestock stalls) onto the space for your garden plot. This will smother existing plants and is best done in fall to be left in place all winter. In spring, till the garden space, turning the straw and manure under. This should be the only time you will need to till the soil. Plant your garden crops immediately, and any areas to be planted later can be seeded to a cover crop. A thick cover crop will smother weeds and will pull carbon from the air while it builds your soil.
Rotate your garden or field crops in a four-year (or more) rotation. (Each kind of plant is grown in a location in the garden or field once every four years.) This will discourage pests and diseases. Mulch your garden; this keeps soil animals alive and keeps soils moist and cool. (Heated or dried soils lose carbon.) As you weed, either compost the weeds or incorporate them into your soil. The best time to add manures or compost is in spring or fall.
Plant shelter belts or hedgerows near or around your garden. These will become homes for pollinators, birds, snakes and other animals beneficial to your garden. Forests, hedgerows and grasslands hold the most carbon on the planet, so hedgerows and shelter belts help reduce emissions.
Do not overgraze or till grasslands, because that will reduce the carbon-holding capacity.
In flower beds and borders, prepare your soil the same way as for vegetables and plant perennial ground covers to act as living mulches. In low-water landscapes, sedums or creeping yarrow planted between larger plants will act as living mulches.
Changing to the regenerative methods of organic gardening and farming will result in lower CO2 emissions, healthy foods, heathy wildlife, clean air and clean water.
Ingram, Dr. Julie, Best Practices for Soil Organic Carbon Management in Agricultural Systems, Countryside & Community Research Institute, UK , 2017
Goode, Cecile M., et. al. Understanding the Impacts of Soil, Climate & Farming Practices on Soil Organic Carbon Sequestration, Australia, 2016
Muchmuller, Megan B., et. al., Emerging Land Use Practices Rapidly Increase Soil Organic Matter, USA, 2015
Zhang, Limimg, et. al, “Toward Optimal Soil Organic Sequestration With Effects of Agriculture Management Practices & Climate Change in Tai-Lake Paddy Soils of China,” In Geoderma, 2016
Smallwood, Mark, Regenerative Organic Agriculture & Climate Change, Rodale Institute, 2013