by Kai Hoffman-Krull
The modern age could very well be termed the age of carbon. We have increased the amount of carbon dioxide in the atmosphere by more than a third since the Industrial Revolution began.1 A gas that keeps heat from the sun contained within the Earth’s atmosphere, carbon dioxide makes up more than three-quarters of the greenhouse gas emissions in the world.2 At the same time agriculture is currently experiencing a carbon crisis, with 50–70 percent of the world’s carbon in farmland soils off-gassed into the atmosphere due to tillage.3 Carbon, known as the building block of life, is the single most essential element in soil fertility as it aids in soil structure development, water retention, nutrient retention, and the biological process.
The decreased fertility from our carbon loss is occurring during a changing climate, when creating resilient crops that can withstand the stress of unpredictable weather patterns will be more important than ever before. The Intergovernmental Panel on Climate Change estimates that global food production could be reduced by up to 17 percent by the year 2100 due to crop failures from increased weather variation.4 The population in the year 2100 is estimated to be 11.2 billion people.5 Finding ways to preserve the carbon in our soil is simultaneously an environmental and social piece of activism, something we can do on our farms to improve our soil health and the health of our climate.
One of the most central carbon retention practices is no-till cultivation. Tillage has contributed 792 billion tons of carbon emissions over the past 250 years.6 In comparison, humans contributed nearly 40 billion tons of carbon dioxide into the atmosphere last year. Tillage introduces unnaturally large amounts of oxygen into the soil, increasing the decomposition of organic matter. As carbon from this organic tissue is freed through the decomposition process, carbon molecules bond with the abundant oxygen introduced through tillage to become CO2, rising into the atmosphere.
If you’ve used tillage and seen impressive results, that’s because tillage is indeed providing a biological bloom momentarily in your soil. By increasing the decomposition of soil organic matter, there is a short-term rise of available labile carbon — the form of carbon that fuels the microbial machinery. While the fungal hyphae are torn and disrupted through tillage, this available labile carbon generates a rise in soil bacteria, which increases the percentage of nutrients that are bio-available for root uptake.
The problem is that tillage is mining this organic carbon at a very quick rate that provides immediate nutrient gain but at a significant long-term cost. A research colleague, Dr. Tom DeLuca at the University of Montana, found that tillage in Midwest prairie soils decreased organic matter levels by 50 percent over a fifteen-year period. The additional concern with this decreased organic matter is that soil carbon levels operate exponentially. Higher rates of organic matter allow for increased nutrients and water to be made available, which in turn increases the production for cover crop and green manure material — two of the foundational methods of increasing soil organics. With decreased organic matter levels, production of both market crops and cover crops decreases over time, making it more difficult to regenerate from the carbon deficiency created through tillage.
My farming mentor, Steve Bensel, once told me that almost everything we do in sustainable agriculture — cover cropping, animal rotations, reduced tillage, composting — are all fundamentally about increasing organic matter in the soil. And when we speak about organic matter we are in large part speaking about carbon, which comprises 58 percent of soil organic matter.7 Organic matter and the carbon within it holds several key roles in soil health:
Carbon is the fuel source that drives the microbial network to digest minerals and make them bio-available to plant roots, also known as mineralization. Without this biological support system processing minerals, plants find it more difficult to access the nutrients available in the soil.
The sugars from composted organic matter pull soil particles into aggregates, providing space that allows soil to store air and water. As this structure diminishes with tillage, soil compacts more and more, requiring higher amounts of disturbance for water, air, and roots to access the subsoil layers.
Organic matter can absorb six times its weight in water, playing a significant role in holding moisture in the soil.8 In addition, the decreased compaction of no-till plots allows for water access through the soil layers, whereas compacted soil creates runoff that carries water and nutrients away. In a four-year study at the University of Nebraska, researchers found that no-till plots saved between two-and-a-half to five inches (65–130 mm) of water per year compared to tilled plots.9
Organic matter increases the soil’s cation exchange capacity, a measure of the soil’s ability to hold nutrients. This means less fertilizer costs each growing season.
No-till systems operate in a manner that mimics natural soil ecosystems — the microbiome, soil animals, and root fibers develop a lattice tunnel system that aerates the ground. Through limiting the loss of organic matter in the soil, no-till methods improve these key soil areas of biological activity, structure, and water and nutrient retention. Unlike tillage, which maximizes benefits in the short term while decreasing soil health over time, no-till systems mature in their fertility. No-till can regenerate compacted, disturbed soils and return carbon back to the ecosystem. No-till is not the only carbon solution we must explore to remediate our depleted croplands nationally and globally, but without it we should all fear for what our children and their children will eat.
If you start using no-till methods, tell your customers and friends. In a time when our government is actively removing environmental regulations, we need to find ways of inviting more of our populace to participate in climate solutions. No-till is a practice you can promote as increasing the quality of your produce, as well as storing carbon in the soil and keeping it from the atmosphere. You can see this as marketing, but also as environmental education — helping people understand the soil carbon crisis and ways they can participate in regenerating our farmlands through their purchasing decisions. And if you aren’t a farmer, tell your co-ops and the farmers at the farmers market you want to buy no-till produce.
For as much as we all use the term sustainable agriculture, few of us contemplate the cost of which we are truly speaking — future famine. We have all lived through the peak of tillage agriculture, where food has been abundant as we have mined our soil resources to maximize immediate food production. Famine only exists for us in stories; it’s something we read about in books, see in movies, or hear about occasionally somewhere else on the globe. Like climate change, it can feel like an abstraction. But famine may not be an abstraction to future generations. We cannot avoid the cost of what our food system has extracted, and some day that debt will need to be paid.
Copernicus started a revolution when he told us that the Earth was not the center of the universe. Today we need a new revolution, one where earth becomes the center of our human universe. We all eat. May this book, and you, be a part of that revolution.
—Kai Hoffman-Krull