For the Soil — with Love!
Published: 2021-12-05Tags: бали слама, почвена смес, зелен палец, калифорнийски червеи, градина в слама, пермакултура, устойчиво земеделие
Translation
This is a translation of a Bulgarian-language post. It conveys the content faithfully but is not the author's original English writing.
December 5th — World Soil Day!
You may know that carbon is the main component of the soil's organic matter, which helps its structure, its capacity to hold water, and its fertility.
But did you know that the agricultural practices of the last century, and conventional farming, are responsible for 50 to 70 percent of the carbon contained in the soil being released into the atmosphere, where, oxidising, it turns into carbon dioxide — the greenhouse gas we know so well, to blame for the ozone hole, global warming, the melting of the glaciers, the disappearance of species… I won't go on!
Instead, I will suggest some simple things anyone can do to help the soil hold more carbon, and even capture more carbon dioxide from the atmosphere, by fixing it in its more stable form — carbon!
It is clear that I am addressing mainly fellow gardeners and farmers, but if you live in the city you can also be part of the change: instead of buying fruit and vegetables from conventional farming at the supermarkets or the market, take the trouble to seek out conscientious farmers who use sustainable practices — and then, besides nature, you and your family will be the winners too, because you will be consuming fresh and clean food!
And now, for those of you with the Green Thumb — the main things you can do to keep the carbon in your soil are to minimise or stop tilling it altogether (#no till Bulgaria), to mulch, to plant more perennial plantings, and to mow at the right height! As is clear, even just in our little garden, or in the yard with a lawn, we can change the way plants and soil interact, by changing the practices we are used to; and using the best of them, in the long term, can reduce greenhouse gases and help the environment!
Now a little science:
In the process of photosynthesis, plants capture carbon dioxide (CO2) from the atmosphere. They convert the carbon dioxide into simple sugars, which they then use for energy and growth, and into structural compounds such as fibre and cellulose. This is the first step of what scientists call carbon capture and storage.
When plants die and their biomass remains in the soil, the insects, worms and microorganisms that inhabit the soil, "eating" it, break down the sugars and the other compounds. One part of the carbon is released back into the atmosphere as carbon dioxide by the microorganisms, and another part of it remains in the soil. There is also plant matter that is harder to break down and becomes part of the soil's organic matter. This is the natural process of carbon capture and retention. Plants capture carbon dioxide — also known to us as a greenhouse gas — and fix it in the soil in its more stable form, carbon.
Of course, the process works in the reverse direction too. Those microorganisms that eat sugar release a little carbon dioxide into the atmosphere — just as we humans do when we exhale!
If you think about the two carbon-dioxide cycles just described, you will understand that our goal should be to increase the plant mass — by improving the growing conditions for the plants (which in turn will use more carbon dioxide) — and to slow the decomposition of the plant residues (which release carbon dioxide). In this way, more carbon is captured and retained in the soil.
Back to the easy practices that help with this: use dry grass (from the mower) as mulch for your garden, and dig (turn over) only where you plan to plant your vegetables! These two things help preserve the carbon in your garden's soil — and the result will be tasty vegetables and a smaller carbon footprint.
Here are more ways to optimise the growth of plants in your yard, which help retain more carbon in the ground:
- Let the grass in your yard grow a little more than usual before you mow it. This encourages more growth of the roots underground too. Longer grass leaves also mean more leaf area — and that means more carbon dioxide is captured from the air. First, you can let the grass grow a bit taller in spring before you mow it. Then leave the cut grass to dry out a little for a day before you rake it up, and finally use it as mulch in your vegetable garden!
- Plant perennial plants! Plants that live longer accumulate biomass — which is made of carbon (the woody stems or trunks and their extensive roots).
Cover your soil — either with plants or with mulch. Bare soil is prone to erosion and does not encourage the best growth of plants. Mulch retains moisture and supplies nutrients to the soil.
Hoe and spade?
Use your garden tools correctly. Reduce the need for the hoe and spade only to when you have soil compaction (which is avoided through mulching) or too many weeds to pull by hand. Unfortunately, classical tilling increases the amount of carbon released from the soil.
What can you do to slow the release of carbon dioxide back into the atmosphere? The decomposition of plant residues in the soil is a good and natural process that releases nutrients for use by other organisms and plants. But it can be managed in ways that slow the amount of carbon dioxide also released. The amount of carbon dioxide released is related to the amounts of oxygen, nitrogen and phosphorus in the soil. When you till the soil to control weeds, you also drive oxygen deeper into the soil.
Reduce, or stop completely, the tilling in your garden! Tilling — ploughing, turning over, cultivating — may help control weeds (for a short time), but it can also accelerate the decomposition of organic matter and help release too much carbon dioxide. In addition, soil organisms often release more carbon dioxide when too much fertiliser is added to the soil — so do not forget to test whether your soil really needs more nutrients before you add fertiliser. You will save money and help the environment by adding only as much fertiliser as your garden needs.
mulch of leaf litter
vegetables mulched with wool
Instead of tilling the soil, choose an alternative way to cultivate your garden — using mulch to control weeds and retain moisture.
Mulching reduces the contact between the organic material and the soil, so the organisms need more time to break it down. The mulch will decompose and its nutrients will be released into the soil, but this happens more slowly, while increasing the organic matter in the soil. If the mulch is left in place from year to year, the soil will be preserved and supplied with nutrients, and this long-term plan will keep the carbon in the garden or the flower bed. Sources of mulch can be grass, leaves, composted garden waste or straw. Besides, fallen leaves are a wonderful mulch, which holds within it the carbon they have absorbed — and there it is, ready in your yard.
At first glance it may not seem that a single person, with their yard or garden, can have any great effect on reducing carbon dioxide in the atmosphere.
But all together, even with the small steps described above that support the growth of plants and slowly return plant residues back into the soil, we can turn carbon dioxide into more stable forms of carbon. There are things we can do; there are things that lead to change!
Credit: personal archive and SSSA